La bibliothèque N. H. Kuiper propose un fonds documentaire spécialisé dans les domaines de recherche de l’Institut et offre à ses lecteurs des services et des produits documentaires variés.

La revue *Les Publications mathématiques de l’IHES* publie les articles des principaux résultats de recherche. De diffusion internationale, elle est reconnue comme l’une des meilleures au monde.

Les prépublications rassemblent l’ensemble des travaux menés à l’Institut et témoignent de l’interdisciplinarité et des collaborations entre professeurs et chercheurs invités.

- La bibliothèque Nicolaas Hendrik Kuiper
- Les Publications mathématiques de l’IHES
- Les prépublications

# La bibliothèque Nicolaas Hendrik Kuiper

Inaugurée le 23 mai 2003, la nouvelle bibliothèque de l’IHES porte le nom du deuxième directeur afin de rendre hommage et d’honorer Nicolaas Hendrik Kuiper. Créée dès l’emménagement de l’Institut à Bures-sur-Yvette en 1962, la bibliothèque se situait initialement dans le pavillon de musique du domaine de Bois-Marie. Aujourd’hui installée au premier étage du bâtiment scientifique, elle offre un cadre propice à l’étude et à l’inspiration des lecteurs, avec une vue sur la nature environnante.

Spécialisée dans les domaines des mathématiques, de la physique théorique et dans toute autre science qui s’y rattache, la bibliothèque Nicolaas Hendrik Kuiper accueille :

– les professeurs permanents,

– les chercheurs invités de l’IHES,

– les chercheurs extérieurs à l’IHES dans les domaines mentionnés à partir du niveau post-doctoral,

– les étudiants de l’université Paris-Saclay des écoles doctorales ou ayant un niveau supérieur au Master 2.

Avec FOCUS, consultez le catalogue et les ressources électroniquesde la bibliothèque

La bibliothèque propose un fonds papier de 10 000 ouvrages environ et 170 périodiques en mathématiques et physique. Un fonds russe est également mis à la disposition des usagers.

Les ressources numériques comprennent les accès aux bases de données (MathScinet, Zentralblatt, ArXiv, Numdam…) et à plus de 13 000 revues électroniques.

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### Informations pratiques

**Heures d’ouverture de la bibliothèque :**

La bibliothèque est accessible 24h sur 24 aux professeurs permanents et les chercheurs invités de l’IHES.

L’accueil des chercheurs extérieurs et des étudiants de l’Université Paris-Saclay est soumis aux horaires de la bibliothécaire, Aurélie Brest.

**Horaires et coordonnées de la bibliothécaire :**

Lundi-mardi-jeudi-vendredi : 9h-12h et 13h30-17h30

Mercredi : 8h30 – 12h00

Contact : 01 60 92 66 98 – bibli@ihes.fr

### Institutions partenaires:

– **RNBM** : Le Réseau National des Bibliothèques de Mathématiques mène une politique documentaire nationale et joue un rôle majeur dans l’accès à la documentation électronique (accords de consortiums) pour la communauté mathématique française. www.rnbm.org

– **CNRS** : La bibliothèque Nicolaas H. Kuiper est une unité mixte de Service (UMS 1786) du CNRS. www.cnrs.fr

– **Université Paris-Saclay** : La bibliothèque Nicolaas H. Kuiper est aussi l’une des bibliothèques membres de l’Université Paris-Saclay.

### Bibliothèques partenaires:

– Bibliothèque Jacques Hadamard

– Bibliothèques de l’Université Paris-Saclay

– Bibliothèque de l’Institut Henri Poincaré

# Les Publications mathématiques de l’IHES

Avec une distribution trilingue et internationale, la revue *Les Publications mathématiques de l’IHES *est l’une des plus prestigieuses revues dans ce domaine.

Créée en 1959 sous l’impulsion de Léon Motchane, et de Jean Dieudonné, professeur de l’institut, la revue *Les Publications mathématiques de l’IHES* paraît au début par fascicules isolés et en quatre langues : français, anglais, allemand et russe (version aujourd’hui abandonnée). Progressivement, l’IHES fait paraître annuellement deux volumes totalisant 800 pages. Depuis 2012, la revue est tirée à 320 exemplaires. Elle est également disponible en ligne et sur numdam.org.

Grâce à sa distribution dans le monde entier (on la trouve dans les bibliothèques de toutes les grandes institutions mathématiques), à sa tradition de publication d’articles historiques et à sa large couverture de la discipline, c’est une revue de haut niveau scientifique qui bénéficie d’une reconnaissance internationale.

Jean Dieudonné est le premier rédacteur en chef de la revue. Jacques Tits lui succède de 1980 à 1998, puis c’est Etienne Ghys qui reprend le poste de rédacteur-en chef jusqu’en 2009.

Le comité de rédaction s’élargit au fil des ans à d’autres professeurs de l’Institut : Pierre Deligne, Dennis Sullivan et René Thom l’intègrent en 1980.

En 1982, Mikhail Gromov rejoint le comité, suivi de Jean Bourgain en 1982, Maxim Kontsevitch en 1996, Laurent Lafforgue en 1999 et Claire Voisin en 2007.

*Les Publications mathématiques de l’IHES* ont été dirigées en 2010 et 2011 par Claire Voisin et Sergiu Klainerman ainsi que par Claire Voisin depuis le 1er janvier 2012.

## Le comité de rédaction actuel

Il est aujourd’hui élargi à des scientifiques extérieurs à l’Institut.

**Rédactrice en chef** : Claire Voisin

**Editeurs** : Viviane Baladi (Institut Mathématique de Jussieu), Philippe Biane (CNRS, Université Marne-la-Vallée, France), Nicolas Bergeron (ENS), Frank Merle (Université Cergy-Pontoise et IHES), Philippe Michel (EPFL, Lausanne, Suisse), Hiraku Nakajima (RIMS, Kyoto, Japon)

**Comité de rédaction** : Jean Bourgain (IAS, Princeton, Etats-Unis), Denis Auroux (University of California, Berkeley), Alain Connes (IHES et Collège de France), Pierre Deligne (IAS, Princeton, Etats-Unis), Mikhail Gromov (IHES), Maxim Kontsevitch (IHES), Dennis Sullivan (CUNY and SUNY, Stony Brook, Etats-Unis)

## Soumettre un article

Pour soumettre un article dans *Les Publications mathématiques de l’IHES*, merci d’adresser votre manuscrit de préférence en fichier pdf à Claire Voisin (voisin@math.jussieu.fr)

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Les Publications Mathématiques de l’IHES

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F-75005 Paris

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La revue est également disponible en ligne et sur numdam.org.

Prépublication | Date | |
---|---|---|

The lure of conformal symmetry P/19/01 Voir plus > Voir moins >The Clifford algebra ${\rm Cl} (4,1) \simeq {\mathbb C} [4]$, generated by the real (Majorana) $\gamma$-matrices and by a hermitian $\gamma_5$, gives room to the reductive Lie algebra $u(2,2)$ of the conformal group extended by the $u(1)$ helicity operator. Its unitary positive energy ladder representations, constructed by Gerhard Mack and the author 50 years ago, opened the way to a better understanding of zero-mass particles and fields and their relation to the space of bound states of the hydrogen atom. They became a prototypical example of a minimal representation of a non-compact reductive group introduced during the subsequent decade by Joseph. |
22/01/2019 | |

Hyperbolic endomorphisms and overlap numbers M/18/10 Voir plus > Voir moins >Hyperbolic endomorphisms and overlap numbers for equilibrium measures are studied on lifts of invariant sets. We look into the structure of Rokhlin conditional measures with respect to various fiber partitions, and find relations between them. We also compute topological overlap numbers in several concrete cases. In particular, we obtain a large class of endomorphisms which asymptotically are irrational-to-1. |
13/11/2018 | |

Some aspects of topological Galois theory M/18/09 Voir plus > Voir moins >We establish a number of results on the subject of the first author's topos-theoretic generalization of Grothendieck's Galois formalism. In particular, we generalize in this context the existence theorem of algebraic closures, we give a concrete description of the atomic completion of a small category whose opposite satisfies the amalgamation pro- perty, and we explore to which extent a model of a Galois-type theory is determined by its symmetries. |
04/09/2018 | |

Three Hopf algebras from number theory, physics and topology, and their common operadic, simplicial and categorical background M/18/08 Voir plus > Voir moins >We consider three a priori totally different setups for Hopf algebras from number theory, mathematical physics and algebraic topology. The primary examples are the Hopf algebras of Goncharov for multiple zeta values, that of Connes--Kreimer for renormalization, and a Hopf algebra constructed by Baues to study double loop spaces. We show that these examples can be successively unified by considering simplicial objects, cooperads with multiplication and Feynman categories at the ultimate level. These considerations open the door to new constructions and reinterpretation of known constructions in a large common framework. |
18/06/2018 | |

On the Ramanujan conjecture for automorphic forms over function fields I. Geometry M/18/07 |
31/05/2018 | |

Global bifurcations of limit cycles in the Leslie-Gover model with the Allee effect M/18/06 Voir plus > Voir moins >In this paper, we complete the global qualitative analysis of the Leslie-Gover system with the Allee effect which models the dynamics of the populations of predators and their prey in a given ecological or biomedical system. In particular, studying global bifurcations, we prove that such a system can have at most two limit cycles surrounding one singular point. We also conduct some numerical experiments to illustrate the obtained results. |
23/05/2018 | |

Multi-parameter planar polynomial dynamical systems M/18/05 Voir plus > Voir moins >In this paper, we study multi-parameter planar dynamical systems and carry out the global bifurcation analysis of such systems. To control the global bifurcations of limit cycle in these systems, it is necessary to know the properties and combine the effects of all their field rotation parameters. It can be done by means of the development of our bifurcational geometric method based on the Wintner-Perko termination principle and application of canonical systems with field rotation parameters. Using this method, we solve, e.g., Hilbert's Sixteenth Problem on the maximum number of limit cycles and their distribution for the general Li\'{e}nard polynomial system and a Holling-type quartic dynamical system. We also conduct some numerical experiments to illustrate the obtained results. |
13/04/2018 | |

Pre-Calabi-Yau algebras as noncommutative Poisson structures M/18/04 Voir plus > Voir moins >We show how the double Poisson algebra introduced in \cite{VdB} appear as a particular part of a pre-Calabi-Yau structure, i.e. cyclically invariant, with respect to the natural inner form, solution of the Maurer-Cartan equation on $Ac part of this solution is described, which is in one-to-one correspondence with the double Poisson algebra structure. As a consequence we have that appropriate pre-Calabi-Yau structures induce a Poisson bracket on representation spaces $({\rm Rep}_n A)^{Gl_n}$ for any associative algebra $A$. |
27/03/2018 | |

Introduction to Higher Cubical Operads. Second Part: The Functor of Fundamental Cubical Weak $\infty$-Groupoids for Spaces M/18/03 |
16/01/2018 | |

Some Aspects of Dynamical Topology: Dynamical Compactness and Slovak Spaces M/18/02 Voir plus > Voir moins >The area of dynamical systems where one investigates dynamical properties that can be described in topological terms is "Topological Dynamics". Investigating the topological properties of spaces and maps that can be described in dynamical terms is in a sense the opposite idea. This area is recently called as "Dynamical Topology". For (discrete) dynamical systems given by compact metric spaces and continuous (surjective) self-maps we (mostly) survey some results on two new notions: "Slovak Space" and "Dynamical Compactness". Slovak space is a dynamical analogue of the rigid space: a nontrivial compact metric space whose homeomorphism group is cyclic and generated by a minimal homeomorphism. Dynamical compactness is a new concept of chaotic dynamics. The omega-limit set of a point is a basic notion in theory of dynamical systems and means the collection of states which "attract" this point while going forward in time. It is always nonempty when the phase space is compact. By changing the time we introduced the notion of the omega-limit set of a point with respect to a Furstenberg family. A dynamical system is called dynamically compact (with respect to a Furstenberg family) if for any point of the phase space this omega-limit set is nonempty. A nice property of dynamical compactness: all dynamical systems are dynamically compact with respect to a Furstenberg family if and only if this family has the finite intersection property. |
08/01/2018 | |

From Euler's play with infinite series to the anomalous magnetic moment P/18/01 |
05/01/2018 | |

Introduction to Higher Cubical Operads. First Part: The Cubical Operad of Cubical Weak $\infty$-Categories M/17/19 |
21/12/2017 | |

In memoriam: Cécile DeWitt-Morette M/17/15 |
08/12/2017 | |

``Ars combinatoria'' chez Gian-Carlo Rota ou le triomphe du symbolisme M/17/18 Voir plus > Voir moins >Gian-Carlos Rota est l'inventeur d'une nouvelle science : la combinatoire algébrique qui n'était jusque-là qu'un ensemble de questions disparates, dont la solution, parfois ingénieuse, ne laissait entrevoir la méthode. Il s'agit ici de décrire la stratégie mise en oeuvre sous sa forme mathématique dont les enjeux philosophiques ne sont pas négligeables, en poursuivant le geste de Rota, pour sortir la combinatoire de son ghetto. |
06/12/2017 | |

Generalized conformal Hamiltonian dynamics and the pattern formation equations M/17/16 Voir plus > Voir moins >We demonstrate the significance of the Jacobi last multiplier in Hamiltonian theory by explicitly constructing the Hamiltonians of certain well known first-order systems of differential equations arising in the activator-inhibitor (AI) systems. We investigate the generalized Hamiltonian dynamics of the AI systems of Turing pattern formation problems, and demonstrate that various subsystems of AI, depending on the choices of parameters, are described either by conformal or contact Hamiltonian dynamics or both. Both these dynamics are subclasses of another dynamics, known as Jacobi mechanics. Furthermore we show that for non Turing pattern formation, like the Gray-Scott model, may actually be described by generalized conformal Hamiltonian dynamics using two Hamiltonians. Finally, we construct a locally defined dissipative Hamiltonian generating function \cite{HHG} of the original system. This generating function coincides with the ``free energy'' of the associated system if it is a pure conformal class. Examples of pattern formation equation are presented to illustrate the method. |
05/12/2017 | |

Study of quasi-integrable and non-holonomic deformation of equations in the NLS and DNLS hierarchy M/17/17 Voir plus > Voir moins >The hierarchy of equations belonging to two different but related integrable systems, the Nonlinear Schrödinger and its derivative variant, DNLS are subjected to two distinct deformation procedures, viz. quasi-integrable deformation (QID) that generally do not preserve the integrability, only asymptotically integrable, and non-holonomic deformation (N HD) that does. QID is carried out generically for the NLS hierarchy while for the DNLS hierarchy, it is first done on the Kaup-Newell system followed by other members of the family. No QI anomaly is observed at the level of EOMs which suggests that at that level the QID may be identified as some integrable deformation. NHD is applied to the NLS hierarchy generally as well as with the specific focus on the NLS equation itself and the coupled KdV type NLS equation. For the DNLS hierarchy, the Kaup-Newell(KN) and Chen-Lee-Liu (CLL) equations are deformed non-holonomically and subsequently, different aspects of the results are discussed. |
05/12/2017 | |

Noncommutative Catalan Numbers M/17/14 Voir plus > Voir moins >The goal of this paper is to introduce and study non-commutative Catalan numbers C_n which belong to the free Laurent polynomial algebra in n generators. Our non-commutative numbers admit interesting (commutative and non-commutative) specializations, one of them related to Garsia-Haiman (q,t)-versions, another to solving non-commutative quadratic equations. We also establish total positivity of the corresponding non-commutative Hankel matrices and introduce accompanying nonc-mmutative binomial coefficients. |
25/08/2017 | |

Theory of Morphogenesis M/17/13 Voir plus > Voir moins >A model of morphogenesis is proposed based upon seven explicit postulates. The mathematical import and biological significance of the postulates are explored and discussed. |
08/06/2017 | |

Spin-orbit precession along eccentric orbits for extreme mass ratio black hole binaries and its effective-one-body transcription P/17/12 |
07/06/2017 | |

Properties of soliton surfaces associated with integrable $\mathbb{C}P^{N-1}$ sigma models P/17/11 Voir plus > Voir moins >We investigate certain properties of $\\mathfrak{su}(N)$-valued two-dimensional soliton surfaces associated with the integrable $\\mathbb{C}P^{N-1}$ sigma models constructed by the orthogonal rank-one Hermitian projectors, which are defined on the two-dimensional Riemann sphere with finite action functional. Several new properties of the projectors mapping onto one-dimensional subspaces as well as their relations with three mutually different immersion formulas, namely, the generalized Weierstrass, Sym-Tafel and Fokas-Gel\'fand have been discussed in detail. Explicit connections among these three surfaces are also established by purely analytical descriptions and, it is demonstrated that the three immersion formulas actually correspond to the single surface parametrized by some specific conditions. |
06/06/2017 | |

q-deformed quadrature operator and optical tomogram P/17/10 Voir plus > Voir moins >In this paper, we define the homodyne q-deformed quadrature operator and find its eigenstates in terms of the deformed Fock states. We find the quadrature representation of q-deformed Fock states in the process. Furthermore, we calculate the explicit analytical expression for the optical tomogram of the q-deformed coherent states. |
22/05/2017 | |

SKEW PRODUCT SMALE ENDOMORPHISMS OVER COUNTABLE SHIFTS OF FINITE TYPE M/17/09 Voir plus > Voir moins >We introduce and study skew product Smale endomorphisms over finitely irreducible topological Markov shifts with countable alphabets. We prove that almost all conditional measures of equilibrium states of summable and locally Holder continuous potentials are dimensionally exact, and that their dimension is equal to the ratio of the (global) entropy and the Lyapunov exponent. We also prove for them a formula of Bowen type for the Hausdorff dimension of all fibers. We develop a version of thermodynamic formalism for finitely irreducible two-sided topological Markov shifts with countable alphabets. We describe then the thermodynamic formalism for Smale skew products over countable-to-1 endomorphisms, and give several applications to measures on natural extensions of endomorphisms. We show that the exact dimensionality of conditional measures on fibers, implies the global exact dimensionality of the measure, in certain cases. We then study equilibrium states for skew products over endomorphisms generated by graph directed Markov systems, in particular for skew products over expanding Markov-Renyi (EMR) maps, and we settle the question of the exact dimensionality of such measures. In particular, this applies to skew products over the continued fractions transformation, and over parabolic maps. We prove next two results related to Diophantine approximation, which make the Doeblin-Lenstra Conjecture more general and more precise, for a different class of measures than in the classical case. In the end, we |
14/05/2017 | |

M-theoretic Lichnerowicz formula and supersymmetry P/17/06 Voir plus > Voir moins >A suitable generalisation of the Lichnerowicz formula can relate the squares of supersymmetric operators to the effective action, the Bianchi identities for fluxes, and some equations of motion. Recently, such formulae have also been shown to underlie the (generalised) geometry of supersymmetric theories. In this paper, we derive an M-theoretic Lichnerowicz formula that describes eleven-dimensional supergravity together with its higher-derivative couplings. The first corrections to the action appear at eight-derivative level, and the construction yields two different supersymmetric invariants, each with a free coefficient. We discuss the restriction of our construction to seven-dimensional internal spaces, and implications for compactifications on manifolds of G 2 holonomy. Inclusion of fluxes and computation of contributions with higher than eight derivatives are also discussed. |
12/05/2017 | |

Modification of Schrodinger-Newton equation due to braneworld models with minimal length P/17/07 Voir plus > Voir moins >We study the correction of the energy spectrum of a gravitational quantum well due to the combined effect of the braneworld model with infinite extra dimensions and generalized uncertainty principle. The correction terms arise from a natural deformation of a semiclassical theory of quantum gravity governed by the Schrodinger-Newton equation based on a minimal length framework. The two fold correction in the energy yields new values of the spectrum, which are closer to the values obtained in the GRANIT experiment. This raises the possibility that the combined theory of the semiclassical quantum gravity and the generalized uncertainty principle may provide an intermediate theory between the semiclassical and the full theory of quantum gravity. We also prepare a schematic experimental set-up which may guide to the understanding of the phenomena in the laboratory. |
12/05/2017 | |

Quantum Supersymmetric Cosmological Billiards and their Hidden Kac-Moody Structure P/17/08 |
12/05/2017 | |

Software modules and computer-assisted proof schemes in the Kontsevich deformation quantization M/17/05 Voir plus > Voir moins >The Kontsevich deformation quantization combines Poisson dynamics, noncommutative geometry, number theory, and calculus of oriented graphs. To manage the algebra and differential calculus of series of weighted graphs, we present software modules: these allow generating the Kontsevich graphs, expanding the non-commutative ⋆-product by using a priori undetermined coefficients, and deriving linear relations between the weights of graphs. Throughout this text we illustrate the assembly of the Kontsevich ⋆-product up to order 4 in the deformation parameter ħ. Already at this stage, the ⋆-product involves hundreds of graphs; expressing all their coefficients via 149 weights of basic graphs (of which 67 weights are now known exactly), we express the remaining 82 weights in terms of only 10 parameters (more specifically, in terms of only 6 parameters modulo gauge-equivalence). Finally, we outline a scheme for computer-assisted proof of the associativity, modulo o(ħ^4), for the newly built ⋆-product expansion. |
11/05/2017 | |

Galois equivariance of critical values of $L$-functions for unitary groups M/17/04 Voir plus > Voir moins >The goal of this paper is to provide a refinement of a formula proved by the first author which expresses some critical values of automorphic $L$-functions on unitary groups as Petersson norms of automorphic forms. Here we provide a Galois equivariant version of the formula. We also give some applications to special values of automorphic representations of $\GL_{n}\times\GL_{1}$. We show that our results are compatible with Deligne's conjecture. |
08/04/2017 | |

Deducing the symmetry of the standard model from the automorphism and structure groups of the exceptional Jordan algebra P/17/03 Voir plus > Voir moins >We continue the study undertaken in [DV] of the exceptional Jordan algebra $J = J_3^8$ as (part of) the finite-dimensional quantum algebra in an almost classical space-time approach to particle physics. Along with reviewing known properties of $J$ and of the associated exceptional Lie groups we argue that the symmetry of the model can be deduced from the Borel-Siebenthal theory of maximal subgroups of simple compact Lie groups. |
30/03/2017 | |

Examples of pre-CY structures, associated operads and cohomologies M/17/02 |
01/02/2017 | |

On the four-loop static contribution to the gravitational interaction potential of two point masses P/17/01 |
19/01/2017 | |

Three-body problem in 3D space: ground state, (quasi)-exact-solvability P/16/29 |
22/11/2016 | |

Diffeomorphisms of quantum fields P/16/28 Voir plus > Voir moins >We study field diffeomorphisms $\Phi(x)= F(\rho(x))=a_0\rho(x)+a_1\rho^2(x)+\ldots=\sum_{j+0}^\infty a_j \rho^{j+1}, $ for free and interacting quantum fields $\Phi$. We find that the theory is invariant under such diffeomorphisms if and only if kinematic renormalization schemes are used. |
07/10/2016 | |

Sur la dualité des topos et de leurs présentations et ses applications : une introduction M/16/26 Voir plus > Voir moins >Ce texte est une version écrite enrichie des notes d'un exposé donné à l'Université de Nantes le 1er avril 2016. Il a été rédigé par le second auteur, à partir de notes succinctes et d'expositions orales du premier auteur. Il peut servir d'introduction à la technique des topos comme ponts et à ses applications, en particulier pour les géomètres peu familiers de la logique catégorique et de la théorie des topos classifiants. |
22/09/2016 | |

Le principe de fonctorialité de Langlands comme un problème de généralisation de la loi d'addition M/16/27 Voir plus > Voir moins >Ce texte représente les notes écrites d'un cours donné à l'Université de Nottingham en juin 2016. Dans la continuité des écrits précédents de l'auteur, il étudie le transfert automorphe de Langlands des groupes réductifs vers les groupes linéaires sous la forme équivalente de la définition d'opérateurs de transformation de Fourier locaux et globaux sur les groupes réductifs induits par les représentations de leurs groupes duaux, d'espaces fonctionnels locaux et globaux fixés par ces opérateurs et d'une fonctionnelle linéaire de Poisson globale qui serait invariante par transformation de Fourier. Se fondant sur une étude du cas des tores, il propose dans le cas des groupes réductifs non abéliens généraux une définition conjecturale des espaces fonctionnels recherchés et une caractérisation conjecturale de la fonctionnelle de Poisson associée. Il montre que la définition des opérateurs de transformations de Fourier et l'éventuelle vérification des propriétés attendues de ces espaces fonctionnels et de cette fonctionnelle de Poisson posent la question cruciale de la construction et de l'étude des opérateurs de convolution (transformés de Fourier de l'opérateur de multiplication point par point des fonctions) associés. Le texte propose pour ces opérateurs de convolution une conjecture d'algébricité qui semble plus raisonnable que la conjecture de "stabilité du tore par convolution" qui avait été faite dans la précédente pr |
22/09/2016 | |

Algebraic flows on Shimura varieties M/16/21 |
15/09/2016 | |

Holomorphic curves in compact Shimura varieties M/16/22 Voir plus > Voir moins >We prove a hyperbolic analogue of the We prove an analogue of the Bloch-Ochiai theorem about the Zariski closure of holomorphic curves in abelian varieties. |
15/09/2016 | |

Structures spéciales et problème de Zilber-Pink M/16/23 Voir plus > Voir moins >The Manin-Mumford and the André-Oort conjectures as well as the one formulated by Zilber and Pink concern algebraic varieties (algebraic tori, Abelian or semi-Abelian varieties, pure or mixed Shimura varieties) endowed with a natural set of special points and special subvarieties. An axiomatisation, in the spirit of model theory, is presented for a description of algebraic varieties endowed with a natural set of special points and special subvarieties with an emphasis on the bi-algebraic nature of the question. The text also reviews recent results on these conjectures. |
15/09/2016 | |

Bi-algebraic geometry and the André-Oort conjecture M/16/24 |
15/09/2016 | |

O-minimal flows on abelian varieties M/16/25 |
15/09/2016 | |

Gravitational scattering, post-Minkowskian approximation and Effective One-Body theory P/16/20 |
09/09/2016 | |

Golod-Shafarevich type theorems and potential algebras M/16/19 Voir plus > Voir moins >Potential algebras feature in the minimal model program and noncommutative resolution of singularities, and the important cases are when they are finite dimensional, or of linear growth. We develop techniques, involving Groebner basis theory and generalized Golod-Shafarevich type theorems for potential algebras, to determine finiteness conditions in terms of the potential. We consider two-generated potential algebras, and prove that they can not have dimension smaller than 8, using Groebner bases arguments, and arguing in terms of associated truncated algebra. We derive from the improved version of the Golod-Shafarevich theorem,that if the potential has only terms of degree 5 or higher, then the potential algebra is infinite dimensional. We prove, that potential algebra for any homogeneous potential of degree n>=3 is infinite dimensional. The proof includes a complete classification of all potentials of degree 3. Then we introduce a certain version of Koszul complex, and prove that in the class P_n of potential algebras with homogeneous potential of degree n+1>= 4, the minimal Hilbert series is H_n=1/1-2t+2t^n-t^{n+1}, so they are all infinite dimensional. Moreover, growth could be polynomial (but at least quadratic) for the potential of degree 4, and is always exponential for potential of degree starting from 5. For one particular type of potential we prove a conjecture by Wemyss, which relates the difference of dimensions of potential algebra and its abelianization with Gopakumar-Vafa invaria |
02/07/2016 | |

Divisor Braids M/16/18 Voir plus > Voir moins >We study a novel type of braid groups on a closed orientable surface Σ. These are fundamental groups of certain manifolds that are hybrids between symmetric products and configuration spaces of points on Σ; a class of examples arises naturally in gauge theory, as moduli spaces of vortices in toric fibre bundles over Σ. The elements of these braid groups, which we call divisor braids, have coloured strands that are allowed to intersect according to rules specified by a graph Γ. In situations where there is more than one strand of each colour, we show that the corresponding braid group admits a metabelian presentation as a central extension of the free Abelian group H_1(Σ;Z)^r, where r is the number of colours, and describe its Abelian commutator. This computation relies crucially on producing a link invariant (of closed divisor braids) in the three-manifold S^1×Σ for each graph Γ. We also describe the von Neumann algebras associated to these groups in terms of rings that are familiar from noncommutative geometry. |
25/05/2016 | |

One question from the Polishchuk and Positselski book on Quadratic algebras M/16/16 Voir plus > Voir moins >In the book 'Quadratic algebras' due to Polishchuk and Positselski algebras with small number of generators (n=2,3) is considered. For some number of relations r possible Hilbert series are listed, and those appearing as series of Koszul algebras are specified. The first case, where it was not possible to do, namely the case of three generators n=3 and three relations r=6 is formulated as an open problem. We give here a complete answer to this question, namely for quadratic algebra A with dim A_1=dim A_2=3 we list all possible Hilbert series, and find out which of them can come from Koszul algebras, and which can not. |
05/05/2016 | |

On the proof of the homology conjecture for monomial non-unital algebras M/16/15 Voir plus > Voir moins >We consider the bar complex of a monomial non-unital associative algebra A=k |
04/05/2016 | |

Periodic subvarieties of a projective variety under the action of a maximal rank abelian group of positive entropy M/16/14 |
19/04/2016 | |

Conservative second-order gravitational self-force on circular orbits and the effective one-body formalism P/16/13 |
01/04/2016 | |

Do the Kontsevich tetrahedral flows preserve or destroy the space of Poisson bi-vectors? M/16/12 Voir plus > Voir moins >We examine two claims from the paper "Formality Conjecture" (Ascona 1996): specifically, that 1) a certain tetrahedral graph flow preserves the class of (real-analytic) Poisson structures, and that 2) another tetrahedral graph flow vanishes at every such Poisson structure. By using twelve Poisson structures with high-order polynomial coefficients as explicit counterexamples, we show that both the above claims are false: neither does the first flow preserve the property of bi-vectors to be Poisson nor does the second flow vanish identically at the Poisson bi-vectors. The counterexamples at hand themselves suggest a correction to the formula for the "exotic" flow on the space of Poisson bi-vectors; in fact, this flow is encoded by the balanced sum involving both the Kontsevich tetrahedral graphs (that give rise to the flows mentioned above). We reveal that it is only the balance (1:6) for which the flow does preserve the space of Poisson bi-vectors. |
31/03/2016 | |

BADLY APPROXIMABLE VECTORS AND FRACTALS DEFINED BY CONFORMAL DYNAMICAL SYSTEMS M/16/10 Voir plus > Voir moins >We prove that if J is the limit set of an irreducible conformal iterated function system (with either finite or countably infinite alphabet), then the badly approximable vectors form a set of full Hausdorff dimension in J. The same is true if J is the radial Julia set of an irreducible meromorphic function (either rational or transcendental). The method of proof is to find subsets of J that support absolutely friendly and Ahlfors regular measures of large dimension. In the appendix to this paper, we answer a question of Broderick, Kleinbock, Reich, Weiss, and the second-named author (’12) by showing that every hyperplane diffuse set supports an absolutely decaying measure. |
22/03/2016 | |

Real Analyticity for random dynamics of transcendental functions M/16/11 Voir plus > Voir moins >Analyticity results of expected pressure and invariant densities in the context of random dynamics of transcendental functions are established. These are obtained by a refinement of work by Rugh \cite{Rug08} leading to a simple approach to analyticity. We work under very mild dynamical assumptions. Just the iterates of the Perron-Frobenius operator are assumed to converge. We also provide a Bowen's formula expressing the almost sure Hausdorff dimension of the radial fiberwise Julia sets in terms of the zero of an expected pressure function. Our main application states real analyticity for the variation of this dimension for suitable hyperbolic random systems of entire or meromorphic functions. |
22/03/2016 | |

SU(N) transitions in M-theory on Calabi-Yau fourfolds and background fluxes P/16/07 Voir plus > Voir moins >We study M-theory on a Calabi-Yau fourfold with a smooth surface S of AN−1 singularities. The resulting three-dimensional theory has a =2 SU(N) gauge theory sector, which we obtain from a twisted dimensional reduction of a seven-dimensional =1 SU(N) gauge theory on the surface S. A variant of the Vafa-Witten equations governs the moduli space of the gauge theory, which, for a trivial SU(N) principal bundle over S, admits a Coulomb and a Higgs branch. In M-theory these two gauge theory branches arise from a resolution and a deformation to smooth Calabi-Yau fourfolds, respectively. We find that the deformed Calabi-Yau fourfold associated to the Higgs branch requires for consistency a non-trivial four-form background flux in M-theory. The flat directions of the flux-induced superpotential are in agreement with the gauge theory prediction for the moduli space of the Higgs branch. We illustrate our findings with explicit examples that realize the Coulomb and Higgs phase transition in Calabi-Yau fourfolds embedded in weighted projective spaces. We generalize and enlarge this class of examples to Calabi-Yau fourfolds embedded in toric varieties with an AN−1 singularity in codimension two. |
09/03/2016 | |

New gravitational self-force analytical results for eccentric orbits around a Schwarzschild black hole P/16/08 |
09/03/2016 | |

High post-Newtonian order gravitational self-force analytical results for eccentric orbits around a Kerr black hole P/16/09 |
09/03/2016 | |

Intermittency in the Hodgkin-Huxley model M/16/06 Voir plus > Voir moins >We show that action potentials in the Hodgkin-Huxley neuron model result from a type I intermittency phenomenon that occurs in the proximity of a saddle-node bifurcation of limit cycles. For the Hodgkin-Huxley spatially extended model, describing propagation of action potential along axons, we show the existence of type I intermittency and a new type of chaotic intermittency, as well as space propagating regular and chaotic diffusion waves. Chaotic intermittency occurs in the transition from a turbulent regime to the resting regime of the transmembrane potential and is characterised by the existence of a sequence of action potential spikes occurring at irregular time intervals. |
26/02/2016 | |

The Langlands-Shahidi method over function fields: the Ramanujan Conjecture and the Riemann Hypothesis for the unitary groups M/16/05 Voir plus > Voir moins >On étudie la méthode de Langlands-Shahidi sur les corps de fonctions de caractéristique p. On prouve la fonctorialité de Langlands globale et locale des groupes unitaires vers les groupes linéaires pour les représentations génériques. Supposant connue la conjecture de Shahidi pour les L-paquets modérés, on donne une extension de la définition des fonctions L et des facteurs ε. Enfin, utilisant le travail de L. Lafforgue, on établit la conjecture de Ramanujan et on prouve que les fonctions L automorphes de Langlands-Shahidi satisfont l'hypothèse de Riemann. |
11/02/2016 | |

Class number problems and Lang conjectures M/16/04 Voir plus > Voir moins >Given a square-free integer d we introduce an affine hypersurface whose integer points are in one-to-one correspondence with ideal classes of the quadratic number field Q(\sqrt{d}). Using this we relate class number problems of Gauss to Lang conjectures. |
01/02/2016 | |

On Emergent Geometry from Entanglement Entropy in Matrix Theory P/16/03 Voir plus > Voir moins >Using Matrix theory, we compute the entanglement entropy between a supergravity probe and modes on a spherical membrane. We demonstrate that a membrane stretched between the probe and the sphere entangles these modes and leads to an expression for the entanglement entropy that encodes information about local gravitational geometry seen by the probe. We propose in particular that this entanglement entropy measures the rate of convergence of geodesics at the location of the probe. |
29/01/2016 | |

Perturbative quantum field theory meets number theory P/16/02 |
27/01/2016 | |

On the conservative dynamics of two-body systems at the fourth post-Newtonian approximation of general relativity P/16/01 |
08/01/2016 | |

Modular Graph Functions P/15/29 Voir plus > Voir moins >We consider properties of modular graph functions, which are non-holomorphic modular functions associated with the Feynman graphs for a conformal scalar field theory on a two-dimensional torus. Such functions arise, for example, in the low energy expansion of genus-one Type II superstring amplitudes. We demonstrate that these functions are sums, with rational coefficients, of special values of single-valued elliptic multiple polylogarithms, which will be introduced in this paper. This insight suggests the many interrelations between these modular graph functions (a few of which were motivated in an earlier paper) may be obtained as a consequence of identities involving elliptic polylogarithms. |
22/12/2015 | |

Cutkosky Rules and Outer Space P/15/34 Voir plus > Voir moins >We derive Cutkosky’s theorem starting from Pham’s classical work. We emphasize structural relations to Outer Space. |
08/12/2015 | |

Higher Chern classes in Iwasawa theory M/15/33 Voir plus > Voir moins >We begin a study of m-th Chern classes and m-th characteristic symbols for Iwasawa modules which are supported in codimension at least m. This extends the classical theory of characteristic ideals and their generators for Iwasawa modules which are torsion, i.e., supported in codimension at least 1. We apply this to an Iwasawa module constructed from an inverse limit of p-parts of ideal class groups of abelian extensions of an imaginary quadratic field. When this module is pseudo-null, which is conjecturally always the case, we determine its second Chern class and show that it has a characteristic symbol given by the Steinberg symbol of two Katz p-adic L-functions. |
05/12/2015 | |

Confirming and improving post-Newtonian and effective-one-body results from self-force computations along eccentric orbits around a Schwarzschild black hole P/15/31 |
04/12/2015 | |

Minisuperspace quantum supersymmetric cosmology (and its hidden hyperbolic Kac-Moody structures) P/15/32 |
04/12/2015 | |

Persistent homology and string vacua P/15/30 Voir plus > Voir moins >We use methods from topological data analysis to study the topological features of certain distributions of string vacua. Topological data analysis is a multi-scale approach used to analyze the topological features of a dataset by identifying which homological characteristics persist over a long range of scales. We apply these techniques in several contexts. We analyze N=2 vacua by focusing on certain distributions of Calabi-Yau varieties and Landau-Ginzburg models. We then turn to flux compactifications and discuss how we can use topological data analysis to extract physical informations. Finally we apply these techniques to certain phenomenologically realistic heterotic models. We discuss the possibility of characterizing string vacua using the topological properties of their distributions. |
03/12/2015 | |

Catégories syntactiques pour les motifs de Nori M/15/26 |
13/11/2015 | |

A new effective-one-body Hamiltonian with next-to-leading order spin-spin coupling P/15/27 |
13/11/2015 | |

Spin-dependent two-body interactions from gravitational self-force computations P/15/28 |
13/11/2015 | |

BPS spectra, barcodes and walls P/15/25 Voir plus > Voir moins >BPS spectra give important insights into the non-perturbative regimes of supersymmetric theories. Often from the study of BPS states one can infer properties of the geometrical or algebraic structures underlying such theories. In this paper we approach this problem from the perspective of persistent homology. Persistent homology is at the base of topological data analysis, which aims at extracting topological features out of a set of points. We use these techniques to investigate the topological properties which characterize the spectra of several supersymmetric models in field and string theory. We discuss how such features change upon crossing walls of marginal stability in a few examples. Then we look at the topological properties of the distributions of BPS invariants in string compactifications on compact threefolds used to engineer black hole microstates. Finally we discuss the interplay between persistent homology and modularity by considering certain number theoretical functions used to count dyons in string compactifications and by studying equivariant elliptic genera in the context of the Mathieu moonshine. |
04/11/2015 | |

Moduli Spaces and Macromolecules M/15/24 Voir plus > Voir moins >Techniques from moduli spaces are applied to biological macromolecules. The first main result provides new a priori constraints on protein geometry discovered empirically and confirmed computationally. The second main result identifies up to homotopy the natural moduli space of several interacting RNA molecules with the Riemann moduli space of a surface with several boundary components in each fixed genus. Applications to RNA folding prediction are discussed. The mathematical and biological frameworks are surveyed and presented from first principles. |
30/10/2015 | |

Smoothness and classicality on eigenvarieties M/15/23 Voir plus > Voir moins >Let p be a prime number and f an overconvergent p-adic automorphic form on a definite unitary group which is split at p. Assume that f is of "classical weight" and that its Galois representation is crystalline at places dividing p, then f is conjectured to be a classical automorphic form. We prove new cases of this conjecture in arbitrary dimension by making crucial use of the "patched eigenvariety". |
07/10/2015 | |

A program for branching problems in the representation theory of real reductive groups M/15/22 Voir plus > Voir moins >We wish to understand how irreducible representations of a group G behave when restricted to a subgroup G' (the branching problem). Our primary concern is with representations of reductive Lie groups, which involve both algebraic and analytic approaches. We divide branching problems into three stages: (A) abstract features of the restriction; (B) branching laws (irreducible decompositions of the restriction); and (C) construction of symmetry breaking operators on geometric models. We could expect a simple and detailed study of branching problems in Stages B and C in the settings that are {\it{a priori}} known to be "nice" in Stage A, and conversely, new results and methods in Stage C that might open another fruitful direction of branching problems including Stage A. The aim of this article is to give new perspectives on the subjects, to explain the methods based on some recent progress, and to raise some conjectures and open questions. |
29/09/2015 | |

Decorated super-Teichmueller space M/15/21 |
25/09/2015 | |

La suite spectrale de Hodge-Tate M/15/20 Voir plus > Voir moins >The Hodge-Tate spectral sequence for a proper smooth variety over a p-adic field provides a framework for us to revisit Faltings' approach to p-adic Hodge theory and to fill in many details. The spectral sequence is obtained from the Cartan-Leray spectral sequence for the canonical projection from the Faltings topos to the étale topos of an integral model of the variety. Its abutment is computed by Faltings' main comparison theorem from which derive all comparison theorems between p-adic étale cohomology and other p-adic cohomologies, and its initial term is related to the sheaf of differential forms by a construction reminiscent of the Cartier isomorphism. |
14/09/2015 | |

On the modular structure of the genus-one Type II superstring low energy expansion P/15/04 Voir plus > Voir moins >The analytic contribution to the low energy expansion of Type II string amplitudes at genus-one is a power series in space-time derivatives with coefficients that are determined by integrals of modular functions over the complex structure modulus of the world-sheet torus. These modular functions are associated with world-sheet vacuum Feynman diagrams and given by multiple sums over the discrete momenta on the torus. In this paper we exhibit exact differential and algebraic relations for a certain infinite class of such modular functions by showing that they satisfy Laplace eigenvalue equations with inhomogeneous terms that are polynomial in non-holomorphic Eisenstein series. Furthermore, we argue that the set of modular functions that contribute to the coefficients of interactions up to order $D^{10} \cR^4$ are linear sums of functions in this class and quadratic polynomials in Eisenstein series and odd Riemann zeta values. Integration over the complex structure results in coefficients of the low energy expansion that are rational numbers multiplying monomials in odd Riemann zeta values. |
02/09/2015 | |

Proof of a modular relation between 1-, 2- and 3-loop Feynman diagrams on a torus P/15/07 Voir plus > Voir moins >The coefficients of the higher-derivative terms in the low energy expansion of genus-one graviton scattering amplitudes are determined by integrating sums of non-holomorphic modular functions over the complex structure modulus of a torus. In the case of the four-graviton amplitude, each of these modular functions is a multiple sum associated with a Feynman diagram for a free massless scalar field on the torus. The lines in each diagram join pairs of vertex insertion points and the number of lines defines its weight $w$, which corresponds to its order in the low energy expansion. Previous results concerning the low energy expansion of the genus-one four-graviton amplitude led to a number of conjectured relations between modular functions of a given $w$, but different numbers of loops $\le w-1$. In this paper we shall prove the simplest of these conjectured relations, namely the one that arises at weight $w=4$ and expresses the three-loop modular function $D_4$ in terms of modular functions with one and two loops. As a byproduct, we prove three intriguing new holomorphic modular identities. |
02/09/2015 | |

More Graviton Physics P/15/05 Voir plus > Voir moins >The interactions of gravitons with spin-1 matter are calculated in parallel with the well known photon case. It is shown that graviton scattering amplitudes can be factorized into a product of familiar electromagnetic forms, and cross sections for various reactions are straightforwardly evaluated using helicity methods. Universality relations are identified. Extrapolation to zero mass yields scattering amplitudes for photon-graviton and graviton-graviton scattering. |
02/09/2015 | |

Fractal Tube Formulas and a Minkowski Measurability Criterion for Compact Subsets of Euclidean Spaces M/15/17 Voir plus > Voir moins >We establish fractal tube formulas valid for a large class of compact subsets (and more generally, relative fractal drums, RFDs) in Euclidean spaces of any dimension. These formulas express the volume of the tubular neighborhoods of the fractal under consideration in terms of the residues of the associated fractal zeta functions and their poles (i.e., the complex dimensions). Under suitable assumptions, we also show that a compact subset of R^N is Minkowski measurable if and only if its only complex dimension of maximum real part is the Minkowski (or box) dimension D of the fractal (or RFD), and D is simple. These results extend to arbitrary dimensions N greater than 1 the corresponding ones obtained by Lapidus and van Frankenhuijsen for fractal strings (i.e., when N =1). We illustrate them by means of several examples. |
27/07/2015 | |

Fractal Zeta Functions and Complex Dimensions of Relative Fractal Drums M/15/14 |
15/07/2015 | |

Distance and Tube Zeta Functions of Fractals and Arbitrary Compact Sets M/15/15 |
15/07/2015 | |

Fractal Zeta Functions and Complex Dimensions: A General Higher-Dimensional Theory M/15/16 |
15/07/2015 | |

Deformation approach to quantisation of field models M/15/13 Voir plus > Voir moins >Associativity-preserving deformation quantisation via Kontsevich's summation over weighted graphs is lifted from the algebras of functions on finite-dimensional Poisson manifolds to the algebras of local functionals within the variational Poisson geometry of gauge fields over the space-time. |
14/07/2015 | |

The Sound of Fractal Strings and the Riemann Hypothesis M/15/11 |
07/07/2015 | |

Towards Quantized Number Theory: Spectral Operators and an Asymmetric Criterion for the Riemann Hypothesis M/15/12 Voir plus > Voir moins >An asymmetric criterion for the Riemann hypothesis is provided, expressed in terms of the invertibility of the spectral operator. This criterion is asymmetric, in the sense that it is valid for all fractal dimensions c in (0,1/2) if and only if the Riemann hypothesis is true, but that (unconditionally) it fails to be true for any value of c in (1/2, 1), a fact which is closely connected to the universality of the Riemann zeta function. |
07/07/2015 | |

Energetics and phasing of nonprecessing spinning coalescing black hole binaries P/15/19 |
28/06/2015 | |

Deformations of complex structures on Riemann surfaces and integrable structures of Whitham type hierarchies M/15/10 Voir plus > Voir moins >We obtain variational formulas for holomorphic objects on Riemann surfaces with respect to arbitrary local coordinates on the moduli space of complex structures. These formulas are written in terms of a canonical object on the moduli space which corresponds to the pairing between the space of quadratic differentials and the tangent space to the moduli space. This canonical object satisfies certain commutation relations which appear to be the same as the ones that emerged in the integrability theory of Whitham type hierarchies. Driven by this observation, we develop the theory of Whitham type hierarchies integrable by hydrodynamic reductions as a theory of certain differential-geometric objects. As an application we prove that the universal Whitham hierarchy is integrable by hydrodynamic reductions. |
12/06/2015 | |

On the large-scale geometry of the $L^p$-metric on the symplectomorphism group of the two-sphere M/15/09 Voir plus > Voir moins >We prove that the vector space $R^d$ of any finite dimension $d$ with the standard metric embeds in a bi-Lipschitz way into the group of area-preserving diffeomorphisms of the two-sphere endowed with the $L^p$-metric for $p>2$. Along the way we show that the $L^p$-metric on this group is unbounded for $p>2$ by elementary methods. |
10/06/2015 | |

The Equivalence Principle in a Quantum World P/15/06 |
20/05/2015 | |

Lectures on Regular and Irregular Holonomic D-modules M/15/08 Voir plus > Voir moins >This is a survey paper based on lectures given by the authors at Ihes, February/March 2015. In a first part, we recall the main results on the tempered holomorphic solutions of D-modules in the language of indsheaves and, as an application, the Riemann-Hilbert correspondence for regular holonomic modules. In a second part, we present the enhanced version of the first part, treating along the same lines the irregular holonomic case. |
18/05/2015 | |

Fourth post-Newtonian effective one-body dynamics P/15/18 |
30/04/2015 | |

Analytic determination of high-order post-Newtonian self-force contributions to gravitational spin precession P/15/17 |
04/03/2015 | |

Detweiler's gauge-invariant redshift variable: analytic determination of the nine and nine-and-a-half post-Newtonian self-force contributions P/15/16 |
09/02/2015 | |

Differential symmetry breaking operators I. General theory and F-method M/15/02 Voir plus > Voir moins >We prove a one-to-one correspondence between differential symmetry breaking operators for equivariant vector bundles over two homogeneous spaces and certain homomorphisms for representations of two Lie algebras, in connection with branching problems of the restriction of representations. We develop a new method (F-method) based on the algebraic Fourier transform for generalized Verma modules, which characterizes differential symmetry breaking operators by means of certain systems of partial differential equations. In contrast to the setting of real flag varieties, continuous symmetry breaking operators of Hermitian symmetric spaces are proved to be differential operators in the holomorphic setting. In this case symmetry breaking operators are characterized by differential equations of second order via the F-method. |
11/01/2015 | |

Differential symmetry breaking operators. II. Rankin--Cohen operators for symmetric pairs M/15/03 Voir plus > Voir moins >Rankin--Cohen brackets are symmetry breaking operators for the tensor product of two holomorphic discrete series representations of SL(2,R). We address a general problem to find explicit formulae, for such intertwining operators in the setting of multiplicity-free branching laws for reductive symmetric pairs. For this purpose we use a new method (F-method) developed in the first part of the series and based on the algebraic Fourier transform for generalized Verma modules. The method characterizes symmetry breaking operators by means of certain systems of partial differential equations of second order. We discover explicit formulae, of new differential symmetry breaking operators for all the six different complex geometries arising from semisimple symmetric pairs of split rank one, and reveal an intrinsic reason why the coefficients of orthogonal polynomials appear in these operators (Rankin--Cohen type) in the three geometries and why normal derivatives are symmetry breaking operators in the other three cases. Further, we analyze a new phenomenon that the multiplicities in the branching laws of Verma modules may jump up at singular parameters. |
11/01/2015 | |

Global uniqueness of small representations M/15/01 Voir plus > Voir moins >We prove that automorphic representations whose local components are certain small representations have multiplicity one. The proof is based on the multiplicity-one theorem for certain functionals of small representations, also proved in this paper. |
04/01/2015 | |

On the integral law of thermal radiation P/14/43 Voir plus > Voir moins >The integral law of thermal radiation by finite size emitters is studied. Two geometrical characteristics of a radiating body or a cavity, its volume and its boundary area, define two terms in its radiance. The term defined by the volume corresponds to the Stefan-Boltzmann law. The term defined by the boundary area is proportional to the third power of temperature and inversely proportional to the emitter's effective size, which is defined as the ratio of its volume to its boundary area. This generalized law is valid for arbitrary temperature and effective size. It is shown that the cubic temperature contribution is observed in experiments. This term explains the intrinsic uncertainty of the NPL experiment on radiometric determination of the Stefan-Boltzmann constant. It is also quantitatively confirmed by data from the NIST calibration of cryogenic blackbodies. Its relevance to the size of source effect in optical radiometry is proposed and supported by the experiments on thermal emission from nano-heaters. |
12/12/2014 | |

On weight modules of algebras of twisted differential operators on the projective space M/14/42 Voir plus > Voir moins >We classify blocks of categories of weight and generalized weight modules of algebras of twisted differential operators on P^n. Necessary and sufficient conditions for these blocks to be tame and proofs that some of the blocks are Koszul are provided. We also establish equivalences of categories between these blocks and categories of bounded and generalized bounded weight sl(n+1)-modules in the cases of nonintegral and singular central character. |
11/12/2014 | |

Topological invariants in magnetohydrodynamics and DNA supercoiling M/14/41 Voir plus > Voir moins >We discuss the structure of topological invariants in two different media. The first example relates to the problem of reconnection in magnetohydrodynamics and the second one to the supercoiling of DNA. Despite the apparently different systems, the behavior of magnetic spread lines and supercoiling process in DNA display some common features based on the existence of topological invariants of Hopf's type. |
10/12/2014 | |

$r_\infty$-Matrices, triangular $L_\infty$-bialgebras, and quantum$_\infty$ groups M/14/40 Voir plus > Voir moins >A homotopy analogue of the notion of a triangular Lie bialgebra is proposed with a goal of extending the basic notions of theory of quantum groups to the context of homotopy algebras and, in particular, introducing a homotopical generalization of the notion of a quantum group, or quantum$_\infty$-group. |
09/12/2014 | |

The calculus of multivectors on noncommutative jet spaces M/14/39 Voir plus > Voir moins >The Leibniz rule for derivations is invariant under cyclic permutations of the co-multiples within the derivations' arguments. We now explore the implications of this fundamental principle, developing the calculus of variations on the infinite jet spaces for maps from sheaves of free associative algebras over commutative manifolds to the quotients of free associative algebras over the linear relation of equivalence under cyclic shifts. In the frames of such variational noncommutative symplectic geometry, we prove the main properties of the Batalin-Vilkovisky Laplacian and variational Schouten bracket. As a by-product of this intrinsically regularised picture, we show that the structures that arise in the classical variational Poisson geometry of infinite-dimensional integrable systems - such as the KdV, NLS, KP, or 2D Toda - do actually not refer to the graded commutativity assumption. |
07/12/2014 | |

Smooth approximation of plurisubharmonic functions on almost complex manifolds M/14/38 Voir plus > Voir moins >This note establishes smooth approximation from above for J-plurisubharmonic functions on an almost complex manifold (X,J). The following theorem is proved. Suppose X is J-pseudoconvex, i.e., X admits a smooth strictly J-plurisubharmonic exhaustion function. Let u be an (upper semi-continuous) J-plurisubharmonic function on X. Then there exists a sequence {u_j} of smooth strictly J-plurisubharmonic functions point-wise decreasing down to u. In any almost complex manifold (X,J) each point has a fundamental neighborhood system of J-pseudoconvex domains, and so the theorem above establishes local smooth approximation on X. This result was proved in complex dimension 2 by the third author, who also showed that the result would hold in general dimensions if a parallel result for continuous approximation were known. This paper establishes the required step by solving the obstacle problem. |
27/11/2014 | |

Une interprétation modulaire de la variété trianguline M/14/37 Voir plus > Voir moins >En utilisant le système de Taylor-Wiles-Kisin construit dans un travail récent de Caraiani, Emerton, Gee, Geraghty, Paškūnas et Shin, nous construisons un analogue de la variété de Hecke. Nous montrons que cette variété coïncide avec une union de composantes irréductibles de l'espace des représentations galoisiennes triangulines. Nous précisons les relations de cette construction avec les conjectures de modularité dans le cas cristallin ainsi qu'avec une conjecture de Breuil sur le socle des vecteurs localement analytiques de la cohomologie complétée. Nous donnons également une preuve d'une conjecture de Bellaïche et Chenevier sur l'anneau local complété en certains points des variétés de Hecke. |
26/11/2014 | |

The BV formalism for L$_\infty$-algebras M/14/36 Voir plus > Voir moins >The notions of a BV$_\infty$-morphism and a category of BV$_\infty$-algebras are investigated. The category of L$_\infty$-algebras with L$_\infty$-morphisms is characterized as a certain subcategory of the category of BV$_\infty$-algebras. This provides a Fourier-dual, BV alternative to the standard characterization of the category of L$_\infty$-algebras as a subcategory of the category of dg cocommutative coalgebras or formal pointed dg manifolds. The functor assigning to a BV$_\infty$-algebra the L$_\infty$-algebra given by higher derived brackets is also shown to have a left adjoint. |
23/10/2014 | |

Graviton-Photon Scattering P/14/32 Voir plus > Voir moins >We use that the gravitational Compton scattering factorizes on the Abelian QED amplitudes to evaluate various gravitational Comp- ton processes. We examine both the QED and gravitational Compton scattering from a massive spin-1 system by the use of helicity am- plitudes. In the case of gravitational Compton scattering we show how the massless limit can be used to evaluate the cross-section for graviton-photon scattering and discuss the difference between photon interactions and the zero mass spin-1 limit. We show that the forward scattering cross-section for graviton photo-production has a very pecu- liar behaviour, differing from the standard Thomson and Rutherford cross-sections for a Coulomb-like potential. |
16/10/2014 | |

Three dimensional Sklyanin algebras and Groebner bases M/14/35 Voir plus > Voir moins >We consider a Sklyanin algebra S with 3 generators, which is the quadratic algebra over a field K with 3 generators x,y,z given by 3 relations pxy+qyx+rzz=0, pyz+qzy+rxx=0 and pzx+qxz+ryy=0. This class of algebras enjoyed much of attention, in particular, using tools from algebraic geometry, Feigin, Odesskii, and Artin, Tate, Van den Berg, showed that if at least two of the parameters p, q and r are non-zero and at least two of three cubes of p, q and r are distinct, then S is Koszul and has the same Hilbert series as the algebra of commutative polynomials in 3 variables. It became commonly accepted, that it is impossible to achieve the same objective by purely algebraic and combinatorial means, like the Groebner basis technique. The main purpose of this paper is to trace the combinatorial meaning of the properties of Sklyanin algebras, such as Koszulity, PBW, PHS, Calabi-Yau, and to give a new constructive proof of the above facts due to Artin, Tate and Van den Bergh. |
14/10/2014 | |

Geometry of Morphogenesis M/14/34 |
01/10/2014 | |

On Koszulity for operads of Conformal Field Theory M/14/31 Voir plus > Voir moins >We study two closely related operads: the Gelfand-Dorfman operad GD and the Conformal Lie Operad CLie. The latter is the operad governing the Lie conformal algebra structure. We prove Koszulity of the Conformal Lie operad using the Gr ̈bner bases theory for operads and an operadic analogue of the Priddy criterion. An example of deformation of an operad coming from the Hom structures is considered. In particular we study possible deformations of the Associative operad from the point of view of the confluence property. Only one deformation, the operad which governs the identity (α(ab))c = a(α(bc)) turns out to be confluent. We introduce a new Hom structure, namely Hom–Gelfand-Dorfman algebras and study their basic properties. |
24/09/2014 | |

The proof of the Kontsevich periodicity conjecture on noncommutative birational transformations M/14/30 Voir plus > Voir moins >For an arbitrary associative unital ring R, let J1 and J2 be the following noncommutative birational partly defined involutions on the set M3 (R) of 3 × 3 matrices over R: J1 (M ) = M −1 (the usual matrix inverse) and J2 (M )jk = (Mkj )−1 (the transpose of the Hadamard inverse). We prove the following surprising conjecture by Kontsevich (1996) saying that (J2 ◦ J1 )3 −1 is the identity map modulo the DiagL × DiagR action (D1 , D2 )(M ) = D1 M D2 of pairs of invertible diagonal matrices. That is, we show that for each M in the domain where (J2 ◦J1 )3 is defined, there are invertible −1 diagonal 3 × 3 matrices D1 = D1 (M ) and D2 = D2 (M ) such that (J2 ◦ J1 )3 (M ) = D1 M D2. |
24/09/2014 | |

Topos-theoretic background M/14/27 Voir plus > Voir moins >This text, which will form the first chapter of my book in preparation "Lattices of theories", is a self-contained introduction to topos theory, geometric logic and the 'bridge' technique. |
23/09/2014 | |

Lattice-ordered abelian groups and perfect MV-algebras: a topos-theoretic perspective M/14/28 Voir plus > Voir moins >We establish, generalizing Di Nola-Lettieri's categorical equivalence, a Morita-equivalence between the theory of lattice-ordered abelian groups and that of perfect MV-algebras. Further, after observing that the two theories are not bi-interpretable in the classical sense, we identify, by considering appropriate topos-theoretic invariants on their common classifying topos, three levels of bi-interpretability holding for particular classes of formulas: irreducible formulas, geometric sentences and imaginaries. Lastly, by investigating the classifying topos of the theory of perfect MV-algebras, we obtain various results on its syntax and semantics also in relation to the cartesian theory of the variety generated by Chang's MV-algebra, including a concrete representation for the finitely presentable models of the latter theory as finite products of finitely presentable perfect MV-algebras. Among the results established on the way, we mention a Morita-equivalence between the theory of lattice-ordered abelian groups and that of cancellative lattice-ordered abelian monoids with bottom element. |
23/09/2014 | |

Quasi-exact-solvability of the $A_2$ elliptic model: Algebraic form, $sl(3)$ hidden algebra, polynomial eigenfunctions P/14/29 |
23/09/2014 | |

Dimensional exactness of self-measures for random countable iterated function systems with overlaps. M/14/26 Voir plus > Voir moins >We study projection measures for random countable (finite or infinite) conformal iterated function systems with arbitrary overlaps. In this setting we extend Feng's and Hu's result from [6] about deterministic finite alphabet iterated function systems. We prove, under a mild assumption offinite entropy, the dimensional exactness of the projections of invariant measures from the shift space, and we give a formula for their dimension, in the context of random infinite conformal iterated function systems with overlaps. There exist numerous differences between our case and the finite deterministic case. We give then applications and concrete estimates for pointwise dimensions of measures, with respect to various classes of random countable IFS with overlaps. Namely, we study several types of randomized systems related to Kahane-Salem sets; also, a random system related to a statistical problem of Sinai; and randomized infinite IFS in the plane for which the number of overlaps is uniformly bounded from above. |
09/09/2014 | |

Principe de fonctorialité et transformations de Fourier non linéaires : proposition de définitions et esquisse d'une possible (?) démonstration M/14/25 Voir plus > Voir moins >Ce texte rassemble les notes écrites d'une série de quatre exposés donnés à l'IHES les 19 juin, 26 juin, 3 juillet et 8 juillet 2014. Il introduit une nouvelle approche pour une éventuelle démonstration - encore à vérifier - du transfert automorphe de Langlands sur les corps globaux. En attendant donc de vérifier soigneusement si cela marche ou bien non, d'abord dans le cas de GL(2) et des représentations de puissances symétriques de son dual. Le point le plus essentiel, sur lequel tout est fondé, est la propriété de stabilité du tore maximal par convolution (définie comme la transformée de Fourier de la multiplication point par point des fonctions) apparue dans la dernière partie de la partie III. |
21/08/2014 | |

Extensions of flat functors and theories of presheaf type M/14/23 Voir plus > Voir moins >We develop a general theory of extensions of flat functors along geometric morphisms of toposes, and apply it to the study of the class of theories whose classifying topos is equivalent to a presheaf topos. As a result, we obtain a characterization theorem providing necessary and sufficient semantic conditions for a theory to be of presheaf type. This theorem subsumes all the previous partial results obtained on the subject and has several corollaries which can be used in practice for testing whether a given theory is of presheaf type as well as for generating new examples of theories belonging to this class. Along the way, we establish a number of other results of independent interest, including developments about colimits in the context of indexed categories, expansions of geometric theories and methods for constructing theories classified by a given presheaf topos. |
26/06/2014 | |

Cyclic theories M/14/22 Voir plus > Voir moins >We describe a geometric theory classified by Connes-Consani's epicylic topos and two related theories respectively classified by the cyclic topos and by the topos $[{\mathbb N}^{\ast}, \Set]$. |
26/06/2014 | |

A Feynman integral via higher normal functions P/14/06 Voir plus > Voir moins >We study the Feynman integral for the three-banana graph defined as the scalar two-point self-energy at three-loop order. The Feynman integral is evaluated for all identical internal masses in two space-time dimensions. Two calculations are given for the Feynman integral; one based on an interpretation of the integral as an inhomogeneous solution of a classical Picard-Fuchs differential equation, and the other using arithmetic algebraic geometry, motivic cohomology, and Eisenstein series. Both methods use the rather special fact that the Feynman integral is a family of regulator periods associated to a family of $K3$ surfaces. We show that the integral is given by a sum of elliptic trilogarithms evaluated at sixth roots of unity. This elliptic trilogarithm value is related to the regulator of a class in the motivic cohomology of the $K3$ family. We prove a conjecture by David Broadhurst that at a special kinematical point the Feynman integral is given by a critical value of the Hasse-Weil $L$-function of the $K3$ surface. This result is shown to be a particular case of Deligne's conjectures relating values of $L$-functions inside the critical strip to periods. |
10/06/2014 | |

Beltrami-Courant Differentials and $G_{\infty}$-algebras M/14/19 Voir plus > Voir moins >Using the symmetry properties of two-dimensional sigma models, we introduce a notion of the Beltrami-Courant differential, so that there is a natural homotopy Gerstenhaber algebra related to it. We conjecture that the generalized Maurer-Cartan equation for the corresponding $L_{\infty}$ subalgebra gives solutions to the Einstein equations. |
06/05/2014 | |

2-CY-tilted algebras that are not Jacobian M/14/17 Voir plus > Voir moins >Over any field of positive characteristic we construct 2-CY-tilted algebras that are not Jacobian algebras of quivers with potentials. As a remedy, we propose an extension of the notion of a potential, called hyperpotential, that allows to prove that certain algebras defined over fields of positive characteristic are 2-CY-tilted even if they do not arise from potentials. In another direction, we compute the fractionally Calabi-Yau dimensions of certain orbit categories of fractionally CY triangulated categories. As an application, we construct a cluster category of type G2. |
29/04/2014 | |

Algebras of quasi-quaternion type M/14/18 Voir plus > Voir moins >We define algebras of quasi-quaternion type, which are symmetric algebras of tame representation type whose stable module category has certain structure similar to that of the algebras of quaternion type introduced by Erdmann. We observe that symmetric tame algebras that are also 2-CY-tilted are of quasi quaternion type. We present a combinatorial construction of such algebras by introducing the notion of triangulation quivers. The class of algebras that we get contains Erdmann's algebras of quaternion type on the one hand and the Jacobian algebras of the quivers with potentials associated by Labardini to triangulations of closed surfaces with punctures on the other hand, hence it serves as a bridge between modular representation theory of finite groups and cluster algebras. |
29/04/2014 | |

SL(2,Z)-invariance and D-instanton contributions to the $D^6 R^4$ interaction P/14/07 Voir plus > Voir moins >The modular invariant coefficient of the $D^6R^4$ interaction in the low energy expansion of type~IIB string theory has been conjectured to be a solution of an inhomogeneous Laplace eigenvalue equation, obtained by considering the toroidal compactification of two-loop Feynman diagrams of eleven-dimensional supergravity. In this paper we determine its exact $SL(2,\Z)$-invariant solution $f(condition as $y\to \infty$ (the weak coupling limit). The solution is presented as a Fourier series with modes $\widehat{f}_n(y) e^{2\pi i n x}$, where the mode coefficients, $\widehat{f}_n(y)$ are bilinear in $K$-Bessel functions. Invariance under $SL(2,\Z)$ requires these modes to satisfy the nontrivial boundary condition $ \widehat{f}_n(y) =O(y^{-2})$ for small $y$, which uniquely determines the solution. The large-$y$ expansion of $f(ower-behaved) terms, together with precisely-determined exponentially decreasing contributions that have the form expected of D-instantons, anti-D-instantons and D-instanton/anti-D-instanton pairs. |
09/04/2014 | |

Algebraic rational cells, equivariant intersection theory, and Poincaré duality M/14/15 Voir plus > Voir moins >We provide a notion of algebraic rational cell with applications to intersection theory on singular varieties with torus action. Based on this notion, we study the algebraic analogue of Q-filtrable varieties: algebraic varieties where a torus acts with isolated fixed points, such that the associated Bialynicki-Birula decomposition consists of algebraic rational cells. We show that the rational equivariant Chow group of any Q-filtrable variety is freely generated by the cell closures. We apply this result to group embeddings, and more general spherical varieties. In view of the localization theorem for equivariant operational Chow rings, we get some conditions for Pointcarré duality in this setting. |
09/04/2014 | |

Motivic Cohomology Spectral Sequence and Steenrod Algebra M/14/16 Voir plus > Voir moins >For an odd prime number $p$, it is shown that differentials $d_n$ in the motivic cohomology spectral sequence with $p$-local coefficients vanish unless $p-1$ divides $n-1$. We obtain an explicit formula for the first non-trivial differential $d_p$, expressing it in terms of motivic Steenrod $p$-power operations and Bockstein homomorphisms. Finally, we construct examples of varieties, having non-trivial differentials $d_p$ in their motivic spectral sequences. |
09/04/2014 | |

Boundedness of non-homogeneous square functions and $L^q$ type testing conditions with $q \in (1,2)$ M/14/14 |
01/04/2014 | |

Calculabilité de la cohomologie étale modulo l M/14/13 |
20/03/2014 | |

Scattering Equations and String Theory Amplitudes P/14/11 Voir plus > Voir moins >Scattering equations for tree-level amplitudes are viewed in the context of string theory. As a result of the comparison we are led to define a new dual model which coincides with string theory in both the small and large $\alpha'$ limit, and whose solution is found algebraically on the surface of solutions to the scattering equations. Because it has support only on the scattering equations, it can be solved exactly, yielding a simple resummed model for $\alpha'$-corrections to all orders. We use the same idea to generalize scattering equations to amplitudes with fermions and any mixture of scalars, gluons and fermions. In all cases checked we find exact agreement with known results. |
19/03/2014 | |

Localization in equivariant operational K-theory and the Chang-Skjelbred property M/14/12 Voir plus > Voir moins >We establish a localization theorem of Borel-Atiyah-Segal type for the equivariant operational K-theory of Anderson and Payne. Inspired by the work of Chang-Skjelbred and Goresky-Kottwitz-MacPherson, we establish a general form of GKM theory in this setting, applicable to singular schemes with torus action. Our results are deduced from those in the smooth case via Gillet-Kimura's technique of cohomological descent for equivariant envelopes. As an application, we extend Uma's description of the equivariant K-theory of smooth compactifications of reductive groups to the equivariant operational K-theory of all, possibly singular, projective group embeddings. |
18/03/2014 | |

The physics of quantum gravity P/14/08 Voir plus > Voir moins >Quantum gravity is still very mysterious and far from being well under- stood. In this text we review the motivations for the quantification of gravity, and some expected physical consequences. We discuss the remarkable rela- tions between scattering processes in quantum gravity and in Yang-Mills theory, and the role of string theory as an unifying theory. |
17/03/2014 | |

Polylogarithms and multizeta values in massless Feynman amplitudes P/14/10 Voir plus > Voir moins >The last two decades have seen a remarkable development of analytic methods in the study of Feynman amplitudes in perturbative quantum field theory. The present lecture offers a physicists' oriented survey of Francis Brown's work on singlevalued multiple polylogarithms, the associated multizeta periods and their application to Schnetz's graphical functions and to $x$-space renormalization. To keep the discussion concrete we restrict attention to explicit examples of primitively divergent graphs in a massless scalar QFT. |
19/02/2014 | |

Particle in a field of two centers in prolate spheroidal coordinates: integrability and solvability P/14/09 |
17/02/2014 | |

The physics and the mixed Hodge structure of Feynman integrals P/14/04 Voir plus > Voir moins >This expository text is an invitation to the relation between quantum field theory Feynman integrals and periods. We first describe the relation between the Feynman parametrization of loop amplitudes and world-line methods, by explaining that the first Symanzik polynomial is the determinant of the period matrix of the graph, and the second Symanzik polynomial is expressed in terms of world-line Green s functions. We then review the relation between Feynman graphs and variations of mixed Hodge structures. Finally, we provide an algorithm for generating the Picard-Fuchs equation satisfied by the all equal mass banana graphs in a two-dimensional space-time to all loop orders. |
14/02/2014 | |

Du transfert automorphe de Langlands aux formules de Poisson non linéaires M/14/05 |
17/01/2014 | |

Non-Abelian Lie algebroids over jet spaces M/14/03 Voir plus > Voir moins >We associate Hamiltonian homological evolutionary vector fields -- which are the non-Abelian variational Lie algebroids' differentials -- with Lie algebra-valued zero-curvature representations for partial differential equations. |
07/01/2014 | |

Une loi de réciprocité explicite pour le polylogarithme elliptique M/14/01 Voir plus > Voir moins >On démontre une compatibilité entre la réalisation p-adique et la réalisation de de Rham des sections de torsion du profaisceau polylogarithme elliptique. La preuve utilise une variante pour H1 de la loi de réciprocité explicite de Kato pour le H2 des courbes modulaires. |
06/01/2014 | |

Le système d'Euler de Kato (II) M/14/02 Voir plus > Voir moins >Ce texte est le deuxième article d’une série de trois articles sur une généralisation de système d’Euler de Kato. Il est consacré e d’Euler de Kato raffiné associé systèmes d’Euler de Kato. |
06/01/2014 | |

Studying Quantum Field Theory P/13/38 |
13/12/2013 | |

Topological pressure and measure-theoretic degrees for non-expanding transformations M/13/39 |
11/12/2013 | |

Density of potentially crystalline representations of fixed weight M/13/37 Voir plus > Voir moins >Let K be a finite extension of Qp. We fix a continuous absolutely irreducible representation of the absolute Galois group of K over a finite dimensional vector space with coefficient in a finite field of characteristic p and consider its universal deformation ring R. If we fix a regular set of Hodge-Tate weights k, we prove, under some hypothesis, that the closed points of Spec(R[1/p]) corresponding to potentially crystalline representations of fixed Hodge-Tate weights k are dense in Spec(R[1/p]) for the Zariski topology. The main hypothesis we need is the existence of a potentially diagonalizable lift, so that in the two-dimensional case, the result is unconditional. |
15/11/2013 | |

Eigenvalues of Laplacian and multi-way isoperimetric constants on weighted Riemannian manifolds M/13/36 Voir plus > Voir moins >We investigate the distribution of eigenvalues of the weighted Laplacian on closed weighted Riemannian manifolds of nonnegative Bakry-s. These inequalities are quantitative versions of the previous theorem by the author with Shioya. We also study some geometric quantity, called multi-way isoperimetric constants, on such manifolds and obtain similar universal inequalities among them. Multi-way isoperimetric constants are generalizations of the Cheeger constant. Extending and following the heat semigroup argument by Ledoux and E. Milman, we extend the Buser-Ledoux result to the k-th eigenvalue and the -way isoperimetric constant. As a consequence the k-th eigenvalue of the weighted Laplacian and the k-way isoperimetric constant are equivalent up to polynomials of k on closed weighted manifolds of nonnegative Bakry- |
21/10/2013 | |

Allure of Quotations and Enchantment of Ideas M/13/35 |
02/10/2013 | |

Ergostructures, Ergologic and the Universal Learning Problem: Chapters 1, 2, 3 M/13/34 |
01/10/2013 | |

Poisson varieties from Riemann surfaces M/13/33 |
30/09/2013 | |

The elliptic dilogarithm for the sunset graph P/13/24 |
24/09/2013 | |

The geometry of variations in Batalin-Vilkovisky formalism M/13/32 Voir plus > Voir moins >We explain why no sources of divergence are built into the Batalin-Vilkovisky (BV) Laplacian, whence there is no need to postulate any ad hoc conventions such as "delta(0)=0" and "log delta(0)=0" within BV-approach to quantisation of gauge systems. Remarkably, the geometry of iterated variations does not refer at all to the construction of Dirac's delta-function as a limit of smooth kernels. We illustrate the reasoning by re-deriving -but not just "formally postulating"- the standard properties of BV-Laplacian and Schouten bracket and by verifying their basic inter-relations (e.g., cohomology preservation by gauge symmetries of the quantum master-equation). |
15/09/2013 | |

On-shell Techniques and Universal Results in Quantum Gravity P/13/23 |
04/09/2013 | |

Quantum supersymmetric cosmology and its hidden Kac--Moody structure P/13/29 |
04/09/2013 | |

Analytical determination of the two-body gravitational interaction potential at the 4th post-Newtonian approximation P/13/30 |
04/09/2013 | |

Merger states and final states of black hole coalescences: a numerical-relativity-assisted effective-one-body approach P/13/31 |
04/09/2013 | |

The tensor hierarchy algebra P/13/27 |
02/09/2013 | |

The tensor hierarchy simplified P/13/28 |
02/09/2013 | |

The Nielsen and the Reidemeister Zeta Functions of maps on infra-solvmanifolds of type (R) M/13/26 Voir plus > Voir moins >We prove the rationality, the functional equations and calculate the radii of convergence of the Nielsen and the Reidemeister zeta functions of continuous maps on infra-solvmanifolds of type (R). We find a connection between the Reidemeister and Nielsen zeta functions and the Reidemeister torsions of the corresponding mapping tori. We show that if the Reidemeister zeta function is defined for a homeomorphism on an infra-solvmanifold of type (R), then this manifold is an infra-nilmanifold. We also prove that a map on an infra-solvmanifold of type (R) induced by an affine map minimizes the topological entropy in its homotopy class and it has a rational Artin-Mazur zeta function. Our main technical tool is the averaging formulas for the Lefschetz, the Nielsen and the Reidemeister numbers on infra-solvmanifolds of type (R). |
30/08/2013 | |

Anyon wave functions and probability distributions P/13/25 Voir plus > Voir moins >The problem of determining the ground state energy for a quantum gas of anyons in two dimensions is considered. A recent approach to this problem by means of lower bounds is here refined to bring out the dependence on the n-particle probability distributions encoded in the wave functions. Furthermore, a class of states which has been proposed in the context of upper bounds for a related many-anyon problem, is here considered from the point of view of these refined lower bounds. A numerical approach to determining their corresponding probability distributions is employed for a limited number of particles. |
06/08/2013 | |

Ramification and nearby cycles for l-adic sheaves on relative curves M/13/22 Voir plus > Voir moins >Deligne and Kato proved a formula computing the dimension of the nearby cycles complex of an l-adic sheaf on a relative curve over an excellent strictly henselian trait. In this article, we reprove this formula using Abbes-Saito’s ramification theory. |
09/07/2013 | |

Conformal and Einstein gravity in twistor space P/13/13 |
18/06/2013 | |

Distributional Geometry of Squashed Cones P/13/21 Voir plus > Voir moins >A regularization procedure developed in \cite{Fursaev:1995ef} for integral curvature invariants on manifolds with conical singularities is generalized to the case of squashed cones. In general, the squashed conical singularities do not have rotational $O(2)$ symmetry in a subspace orthogonal to a singular surface $\Sigma$ so that the surface is allowed to have extrinsic curvatures. A new feature of squashed conical singularities is that the surface terms in the integral invariants, in the limit of small angle deficit, now depend also on the extrinsic curvatures of $\Sigma$. A case of invariants which are quadratic polynomials of the Riemann curvature is elaborated in different dimensions and applied to several problems related to entanglement entropy. The results are in complete agreement with computations of the logarithmic terms in entanglement entropy of 4D conformal theories \cite{Solodukhin:2008dh}. Among other applications of the suggested method are logarithmic terms in entanglement entropy of non-conformal theories and a holographic formula of entanglement entropy for theories with gravity duals. |
17/06/2013 | |

Nonholonomic deformation of coupled and supersymmetric KdV equation and Euler-Poincaré-Suslov method M/13/15 Voir plus > Voir moins >Recently Kupershmidt \cite{Kup} presented a Lie algebraic derivation of a new sixth-order wave equation, which was proposed by Karasu-Kalkani et al \cite{KKK}. In this paper we demonstrate that Kupershmidt's method can be interpreted as an infinite-dimensional analogue of the Euler-Poincarnsional construction to construct nonholonomic deformation of a wide class of coupled KdV equations, all these equations follow from the Euler-PoincarS^1) \bo C^{\infty}(S^1)}}$, where $Diff(S^1)$ is the group of orientation preserving diffeomorphisms on a circle. We generalize our construction to two component Camassa-Holm equation. We also give a derivation of a nonholonomic deformation of the $N=1$ supersymmetric KdV equation, dubbed as sKdV6 equation and this method can be interpreted as an infinite-dimensional supersymmetric analogue of the Euler-Poincar |
14/06/2013 | |

Application of Jacobi's last multiplier for construction of singular Hamiltonian of the activator-inhibitor model and conformal Hamiltonian dynamics M/13/16 Voir plus > Voir moins >The relationship between Jacobi's last multiplier and the Lagrangian of a second-order ordinary differential equation is quite well known. In this article we demonstrate the significance of the last multiplier in Hamiltonian theory by explicitly constructing the Hamiltonians of certain well known first-order systems of differential equations arising in the activator and inhibitor model and these are connected to conformal Hamiltonian structure. |
14/06/2013 | |

The role of the Jacobi Last Multiplier in Nonholonomic Systems and Almost Symplectic Structure M/13/17 Voir plus > Voir moins >The relationship between Jacobi's last multiplier (JLM) and nonholonomic systems endowed with the almost symplectic structure is elucidated in this paper. In particular, we present an algorithmic way to describe how the two form and almost Poisson structure associated to nonholonomic system, studied by L. Bates and his coworkers, can be mapped to symplectic form and canonical Poisson structure using JLM. We demonstrate how JLM can be used to map an integrable nonholonomic system to a Liouville integrable system. We map the toral fibration defined by the common level sets of the integrals of a Liouville integrable Hamiltonian system with a toral fibration coming from a completely integrable nonholonomic system. |
14/06/2013 | |

Contiguity relations for linearisable systems of Gambier type P/13/18 Voir plus > Voir moins >We introduce the Schlesinger transformations for the Gambier, linearisable, equation and by combining the former construct the contiguity relations of the solutions of the latter. We extend the approach to the discrete domain obtaining thus the Schlesinger transformations and the contiguity relations of the solutions of the Gambier mapping. In all cases the resulting contiguity relation is a linearisable equation, involving free functions, and which can be related to the generic Gambier mapping. |
14/06/2013 | |

Quantum aspects of the Liénard II equation and Jacobi's Last Multiplier-II P/13/19 Voir plus > Voir moins >This is a continuation of the paper [J. Phys. A: Math. Theor. 46 (2013) 165202], in which we mapped the Lis ordering technique. In this paper we present further results on the construction of three sets of exactly solvable potentials giving rise to bound-state solutions of the Schr |
14/06/2013 | |

Chemotherapy in heterogeneous cultures of cancer cells with interconversion M/13/20 Voir plus > Voir moins >Recently, it has been observed the interconversion between differentiated and stem-like cancer cells. Here, we model the \textit{in vitro} growth of heterogeneous cell cultures in the presence of interconversion from differentiated cancer cells to cancer stem cells, showing that, targeting only cancer stem cells with cytotoxic agents, it is not always possible to eradicate cancer. We have determined the kinetic conditions under which cytotoxic agents in \textit{in vitro} heterogeneous cultures of cancer cells eradicate cancer. In particular, we have shown that the chemotherapeutic elimination of \textit{in vitro} cultures of heterogeneous cancer cells is effective if it targets all the cancer cell types, and if the induced death rates for the different subpopulations of cancer cell types are large enough. |
14/06/2013 | |

Nouveaux développements sur les valeurs des caractères des groupes symétriques; méthodes combinatoires M/13/14 Voir plus > Voir moins >L’étude asymptotique des diagrammes de Young de grande taille a été entreprise cu dans le but de contrôler les algèbres d’opérateurs liées aux groupes libres ; elles ont servi ensuite tude des zéros de la fonction zeta de Riemann. Plus récemment , elles ont été appliquées par Biane aux propriétés asymptotiques des permutations. Nous insisterons surtout sur les formules exactes qui sous-tendent ces formules asymptotiques obtenues par les collaborateurs de Biane (Sniady, Féray), et qui développent de nouveaux domaines de la combinatoire (principalement cartes planaires). |
05/06/2013 | |

Truncated Infinitesimal Shifts, Spectral Operators and Quantized Universality of the Riemann Zeta Function M/13/12 |
15/05/2013 | |

mRNA diffusion as a mechanism of morphogenesis in Drosophila early development M/13/11 Voir plus > Voir moins >In Drosophila early development, bicoid mRNA of maternal origin is deposited in one of the poles of the egg, determining the anterior tip of the embryo and the position of the head of larvae. The deposition of mRNAs is done during oogenesis by the mother ovary cells and is transported into the oocyte along microtubules. Initially, the oocyte has only one nucleus, but after fertilization and deposition of the egg, nuclear duplication by mitosis is initiated without the formation of cellular membranes. During the first 14 nuclear divisions of the developing embryo, bicoid mRNA of maternal origin is translated into protein in the ribosomes and accumulates near the external nuclear walls of the recently formed nuclei. Here, we show that mRNA diffusion is the main morphogenesis mechanism explaining consistently the establishment of Bicoid protein gradients. Moreover, we show that if diffusion for both bicoid mRNA and Bicoid protein were assumed, a steady distribution of Bicoid protein would result, with a constant concentration along the embryo, contradicting observations. |
29/04/2013 | |

Equivariant operational Chow rings of spherical varieties and T-linear varieties. M/13/10 Voir plus > Voir moins >We stablish localization theorems for the equivariant operational Chow rings (or equivariant Chow cohomology) of singular spherical varieties and T-linear varieties. Our main results provide a GKM description of these rings in the case of spherical varieties admitting a BB-decomposition into algebraic rational cells. Our description extends certain topological results to intersection theory on singular varieties. |
12/04/2013 | |

Dynamic trajectory control of gliders M/13/09 Voir plus > Voir moins >A new dynamic control algorithm in order to direct the trajectory of a glider to a pre-assigned target point is proposed. The algorithm runs iteratively and the approach to the target point is self-correcting. The algorithm is applicable to any non-powered lift-enabled vehicle (glider) travelling in planetary atmospheres. As a proof of concept, we have applied the new algorithm to the command and control of the trajectory of the Space Shuttle during the Terminal Area Energy Management (TAEM) phase. |
04/04/2013 | |

Chemotaxis with directional sensing during Dictyostelium aggregation M/13/07 Voir plus > Voir moins >With an in silico analysis, we show that the chemotactic movements of colonies of the starving amoeba Dictyostelium discoideum are driven by a force that depends on both the direction of propagation (directional sensing) of reaction-diffusion chemotactic waves and on the gradient of the concentration of the chemoattractant. It is shown that the directional sensing of amoebae is due to the sensitivity of the cells to the time variation of the concentration of the chemoattractant combined with its gradient. It is also shown that chemotaxis exclusively driven by local concentration gradients leads to unstable local motion, preventing cells from aggregation. These facts show that the formation of mounds, which initiate multicellularity in Dictyostelium discoideum, is caused by the sensitivity of the amoebae to three factors, namely, to the direction of propagation of the chemoattractant, to its gradient, and to the spiral spatial topology of the propagating chemoattractant. |
24/03/2013 | |

The regulation of gene expression in eukaryotes: bistability and oscillations in repressilator models M/13/08 Voir plus > Voir moins >To model the regulation of gene expression in eukaryotes by transcriptional activators and repressors, we introduce delays in conjugation with the mass action law. Delays are associated with the time gap between the mRNA transcription in the nucleoplasm and the protein synthesis in the cytoplasm. After re-parameterisation of the m-repressilator model with the Hill cooperative parameter n, for n=1, the m-repressilator is deductible from the mass action law and, in the limit $n \to \infty$, it is a Boolean type model. With this embedding and with delays, if m is odd and n>1, we show that there is always a choice of parameters for which the m-repressilator model has sustained oscillations (limit cycles), implying that the 1-repressilator is the simplest genetic mechanism leading to sustained oscillations in eukaryotes. If m is even and n>1, there is always a choice of parameters for which the m-repressilator model has bistability. |
24/03/2013 | |

Noyaux du transfert automorphe de Langlands et formules de Poisson non linéaires: Notes de cours M/13/06 |
18/02/2013 | |

On weakly group-theoretical non-degenerate braided fusion categories M/13/05 Voir plus > Voir moins >We show that the Witt class of a weakly group-theoretical non-degenerate braided fusion category belongs to the subgroup generated by classes of non-degenerate pointed braided fusion categories and Ising braided categories. This applies in particular to solvable non-degenerate braided fusion categories. We also give some sufficient conditions for a braided fusion category to be weakly group-theoretical or solvable in terms of the factorization of its Frobenius-Perron dimension and the Frobenius-Perron dimensions of its simple objects. As an application, we prove that every non-degenerate braided fusion category whose Frobenius-Perron dimension is a natural number less than 1800, or an odd natural number less than 33075, is weakly group-theoretical. |
01/02/2013 | |

Special Functions in Minimal Representations M/13/04 Voir plus > Voir moins >Minimal representations of a real reductive group G are the `smallest' irreducible unitary representations of G. We discuss special functions that arise in the analysis of L^2-model of minimal representations. |
22/01/2013 | |

Rankin-Cohen Operators for Symmetric Pairs M/13/03 |
10/01/2013 | |

Sur la correspondance de Simpson p-adique. II : aspects globaux M/13/02 Voir plus > Voir moins >We develop a new approach for the p-adic Simpson correspondence, closely related to the original approach of Faltings, but also inspired by the work of Ogus and Vologodsky on an analogue in characteristic p>0. This second article is devoted to the global aspects of the theory. |
09/01/2013 | |

Sur la correspondance de Simpson p-adique. 0 : une vue d'ensemble M/13/01 Voir plus > Voir moins >We develop a new approach for the p-adic Simpson correspondence, closely related to the original approach of Faltings, but also inspired by the work of Ogus and Vologodsky on an analogue in characteristic p>0. The aim of this article is to give an extensive overview of the theory that has been developped in two articles, the first one (arXiv:1102.5466) devoted to the local aspects and the second one (arXiv:1301.0904) to the global aspects. |
09/01/2013 | |

F-method for constructing equivariant differential operators M/12/36 Voir plus > Voir moins >Using an algebraic Fourier transform of operators, we develop a method (F-method) to obtain explicit highest weight vectors in the branching laws by differential equations. This article gives a brief explanation of the F-method and its applications to a concrete construction of some natural equivariant operators that arise in parabolic geometry and in automorphic forms. |
31/12/2012 | |

Gravitational self-force and the effective-one-body formalism between the innermost stable circular orbit and the light ring P/12/35 |
10/12/2012 | |

Gravitational radiation reaction along general orbits in the effective one-body formalism P/12/34 |
10/12/2012 | |

Minkowski Measurability Results for Self-Similar Tilings and Fractals with Monophase Generators M/12/33 |
04/12/2012 | |

Dirac Operators and Geodesic Metric on the Harmonic Sierpinski Gasket and Other Fractal Sets M/12/32 |
02/12/2012 | |

The Decimation Method for Laplacians on Fractals: Spectra and Complex Dynamics M/12/31 |
27/11/2012 | |

Towards an axiomatic geometry of fundamental interactions in noncommutative space-time at Planck scale P/12/30 Voir plus > Voir moins >We outline an axiomatic quantum picture unifying the four fundamental interactions; this is done by exploring a possible physical meaning of the notions, structures, and logic in a class of noncommutative geometries which has been introduced in [IHES/M-12-13]. We try to recognise a mathematical formalisation of such phenomena of Nature as the oriented space-time, gravity (here, dark matter and vacuum energy), Hubble's law, inflation, formation and structure of sub-atomic particles, antimatter, annihilation, CP-symmetry violation, mass and mass endowment mechanism, three lepton-neutrino matchings, spin, helicity and chirality, electric charge and electromagnetism, as well as the weak and strong interaction between particles, admissible transition mechanisms (e.g., muon to muon neutrino, electron, and electron antineutrino), and decays (e.g., neutron to proton, electron, and electron antineutrino). Our approach is based on the understanding of Physics as text which is written in the language of affine Lie algebras and associated homeo-class noncommutative structures over the space-time. |
12/11/2012 | |

Temperedness of Reductive Homogeneous Spaces M/12/29 Voir plus > Voir moins >Let G be a semisimple algebraic Lie group and H a reductive subgroup. We compute geometrically the best even integer p for which the representation of G in L^2(G/H) is almost L^p. As an application, we give a criterion which detects whether this representation is tempered. |
05/11/2012 | |

Noyaux du transfert automorphe de Langlands et formules de Poisson non lin\'eaires M/12/28 Voir plus > Voir moins >On montre qu'un certain type de formules de Poisson non lin'eaires explicites, qui est impliqu'e par le principe de fonctorialit'e de Langlands, permet de construire des ``noyaux'' du transfert automorphe. Il y a donc 'equivalence entre le principe de fonctorialit'e et ces formules de Poisson non lin'eaires. |
29/10/2012 | |

The Current State of Fractal Billiards M/12/27 |
16/10/2012 | |

Varna Lecture on $L^2$-Analysis of Minimal Representations M/12/26 Voir plus > Voir moins >Minimal representations of a real reductive group G are the 'smallest' irreducible unitary representations of G. The author suggests a program of global analysis built on minimal representations from the philosophy: 'small' representation of a group = 'large' symmetries in a representation space. This viewpoint serves as a driving force to interact algebraic representation theory with geometric analysis of minimal representations, yielding a rapid progress on the program. We give a brief guidance to recent works with emphasis on the Schroedinger model. |
12/10/2012 | |

Fractal Complex Dimensions, Riemann Hypothesis and Invertibility of the Spectral Operator M/12/25 |
30/09/2012 | |

Discrete Spectrum for non-Riemannian Locally Symmetric Spaces --- I. Construction and Stability M/12/24 Voir plus > Voir moins >We study the discrete spectrum of the Laplacian on certain pseudo-Riemannian manifolds M which are quotients of reductive symmetric spaces X by discrete groups of isometries acting properly discontinuously. Assuming that X admits a maximal compact subsymmetric space of full rank, we construct L^2-eigenfunctions on M for an infinite set of eigenvalues. In contrast to the classical setting where the nonzero discrete spectrum varies on the Teichmüller space of a compact Riemann surface, we prove that this infinite set of eigenvalues is stable under any small deformation of discrete groups, for a large class of groups. We actually construct joint L2-eigenfunctions for the whole commutative algebra of invariant differential operators on M. |
19/09/2012 | |

Minkowski Measurability and Exact Fractal Tube Formulas for p-Adic Self-Similar Strings M/12/23 |
14/08/2012 | |

One-Loop four-graviton amplitudes in N=4 supergravity models P/12/21 |
13/08/2012 | |

From Global to Local M/12/18 |
27/07/2012 | |

The zero locus of the infinitesimal invariant M/12/20 Voir plus > Voir moins >Let $\nu$ be a normal function on a complex manifold $X$. The infinitesimal invariant of $\nu$ has a well-defined zero locus inside the tangent bundle $TX$. When $X$ is quasi-projective, and $\nu$ is admissible, we show that this zero locus is constructible in the Zariski topology. |
27/07/2012 | |

Box-Counting Fractal Strings, Zeta Functions, and Equivalent Forms of Minkowski Dimension M/12/22 |
27/07/2012 | |

Multifractal Analysis via Scaling Zeta Functions and Recursive Structure of Lattice Strings M/12/19 |
26/07/2012 | |

On dimension growth of groups M/12/17 Voir plus > Voir moins >The (asymptotic) dimension growth functions of groups were introduced by Gromov in 1999. In this paper, we show connections between dimension growth and expansion properties of graphs, Ramsey theory and the Kolmogorov-Ostrand dimension of groups and prove that all solvable subgroups of the R.Thompson group F have polynomial dimension growth. We introduce controlled dimension growth function and prove that the exponentially controlled dimension growth is exponential for the Thompson group F and some solvable of class 3 groups. The paper contains many open questions. |
24/07/2012 | |

Sequences of Compatible Periodic Hybrid Orbits of Prefractal Koch Snowflake Billiards M/12/16 |
18/07/2012 | |

Partition Zeta Functions, Multifractal Spectra, and Tapestries of Complex Dimensions M/12/15 |
11/07/2012 | |

The twelve lectures in the (non)commutative geometry of differential equations M/12/13 Voir plus > Voir moins >These notes follow the twelve-lecture course in the geometry of nonlinear partial differential equations of mathematical physics. Briefly yet systematically, we outline the geometric and algebraic structures associated with such equations and study the properties of these structures and their inter-relations. The lectures cover the standard material about the infinite jet bundles, systems of differential equations (e.g., Lagrangian or Hamiltonian), their symmetries and conservation laws (together with the First and Second Noether Theorems), and the construction of the nonlocalities. Besides, in the lectures we introduce the calculus of variational multivectors --- in terms of the Schouten bracket, or the antibracket --- on the (non)commutative jet spaces and proceed with its applications to the variational Poisson formalism and the BRST- or BV-approach to the gauge systems. The course differs from other texts on the subject by its greater emphasis on the physics that motivates the model geometries. Simultaneously, the course attests to the applicability of the algebraic techniques in the analysis of the geometry of fundamental interactions. These lectures could be a precursor to the study of the (quantum) field and string theory. |
02/07/2012 | |

Hyperfunctions and Spectral Zeta Functions of Laplacians on Self-Similar Fractals M/12/14 |
02/07/2012 | |

Effective action approach to higher-order relativistic tidal interactions in binary systems and their effective one body description P/12/10 |
29/06/2012 | |

Theoretical aspects of the equivalence principle P/12/11 |
29/06/2012 | |

Measurability of the tidal polarizability of neutron stars in late-inspiral gravitational-wave signals P/12/12 |
29/06/2012 | |

Riemann Zeroes and Phase Transitions via the Spectral Operator on Fractal Strings M/12/09 |
09/06/2012 | |

Gravity, strings, modular and quasimodular forms P/12/08 |
09/05/2012 | |

On the Tutte-Krushkal-Renardy polynomial for cell complexes M/12/07 Voir plus > Voir moins >Recently V.Krushkal and D.Renardy generalized the Tutte polynomial from graphs to cell complexes. We show that evaluating this polynomial at the origin gives the number of cellular spanning trees in the sense of A.~Duval, C.~Klivans, and J.~Martin. Moreover, after a slight modification, the Tutte-Krushkal-Renardy polynomial evaluated at the origin gives a weighted count of cellular spanning trees, and therefore its free term can be calculated by the cellular matrix-tree theorem of Duval et al. In the case of cell decomposition of a sphere, this modified polynomial satisfies the same duality identity as before. We find that evaluating the Tutte-Krushkal-Renardy along a certain line is the Bott polynomial. Finally we prove skein relations for the Tutte-Krushkal-Renardy polynomial. |
16/04/2012 | |

Hopf Galois (Co)Extensions In Noncommutative Geometry M/12/06 Voir plus > Voir moins >We introduce an alternative proof, with the use of tools and notions for Hopf algebras, to show that Hopf Galois coextensions of coalgebras are the sources of stable anti Yetter-Drinfeld modules. Furthermore we show that two natural cohomology theories related to a Hopf Galois coextension are isomorphic. |
10/04/2012 | |

Location of the Lee-Yang zeros and absence of phase transitions in some Ising spin systems P/12/05 |
03/04/2012 | |

On Generalizations of Connes-Moscovici Characteristic Map M/12/04 Voir plus > Voir moins >In this paper we generalize the Connes-Moscovici characteristic map for cyclic cohomology of extended version of Hopf algebras called x-Hopf algebras. To do this, we define a pairing for cyclic cohomology of module algebras and module coalgebras under the symmetry of a x-Hopf algebra. We introduce more examples of similar generalized characteristic maps for quantum algebraic torus and enveloping algebras. |
12/03/2012 | |

Algebras for Amplitudes P/12/03 Voir plus > Voir moins >Tree-level amplitudes of gauge theories are expressed in a basis of auxiliary amplitudes with only cubic vertices. The vertices in this formalism are explicitly factorized in color and kinematics, clarifying the color-kinematics duality in gauge theory amplitudes. The basis is constructed making use of the KK and BCJ relations, thereby showing precisely how these relations underlie the color-kinematics duality. We express gravity amplitudes in terms of a related basis of color-dressed gauge theory amplitudes, with basis coefficients which are permutation symmetric. |
05/03/2012 | |

A $R^4$ non-renormalisation theorem in ${\mathcal N} = 4$ supergravity P/12/02 |
17/02/2012 | |

Quantization is a mystery P/12/01 Voir plus > Voir moins >Expository notes which combine a historical survey of the development of quantum physics with a review of selected mathematical topics in quantization theory (addressed to students who have had a first course in quantum mechanics). After recalling in the introduction the early stages of the quantum revolution, and recapitulating in Sect. 2.1 some basic notions of symplectic geometry, we survey in Sect. 2.2 the so called {\it prequantization} thus preparing the ground for an outline of {\it geometric quantization} (Sect. 2.3). In Sect. 3 we apply the general theory to the study of basic examples of {\it quantization of K"ahler manifolds}. In Sect. 4 we review the Weyl and Wigner maps and the work of Groenewold and Moyal that laid the foundations of {\it quantum mechanics in phase space}, ending with a brief survey of the modern development of {\it deformation quantization}. Sect. 5 provides a review of {\it second quantization} and its mathematical interpretation. We point out that the treatment of (nonrelativistic) bound states requires going beyond the neat mathematical formalization of the concept of second quantization. An appendix is devoted to Pascual Jordan, the least known among the creators of quantum mechanics and the chief architect of the ``theory of quantized matter waves''. |
31/01/2012 | |

Spatial variation of fundamental couplings and Lunar Laser Ranging P/11/30 |
22/12/2011 | |

Energy versus Angular Momentum in Black Hole Binaries P/11/31 |
22/12/2011 | |

History of Mathematics from a working mathematician's view M/11/29 |
12/12/2011 | |

SMALL REPRESENTATIONS, STRING INSTANTONS, AND FOURIER MODES OF EISENSTEIN SERIES P/11/25 |
21/11/2011 | |

A Juzvinski\u{i} Addition Theorem for Finitely Generated Free Groups Actions M/11/28 Voir plus > Voir moins >The classical Juzvinski\u{i} Addition Theorem states that the entropy of an automorphism of a compact group decomposes along invariant subgroups. Thomas generalized the theorem to a skew-product setting. Using L. Bowen's f-invariant we prove the addition theorem for actions of finitely generated free groups on skew-products with compact totally disconnected groups or finitely dimensional Lie Groups and discuss examples. |
17/11/2011 | |

Homological evolutionary vector fields in Korteweg-de Vries, Liouville, Maxwell, and several other models M/11/26 |
16/11/2011 | |

Symplectic structures on moduli spaces of framed sheaves on surfaces M/11/27 Voir plus > Voir moins >We provide generalizations of the notions of Atiyah class and the Kodaira-Spencer map to the case of framed sheaves. Moreover, we construct closed two-forms on the moduli spaces of framed sheaves on surfaces. As an application, we dene a symplectic structure on the moduli spaces of framed sheaves on the second Hirzebruch surface. This generalizes a result of Bottacin for the locally free case. |
15/11/2011 | |

N=4 SYM Regge Amplitudes and Minimal Surfaces in AdS/CFT Correspondence P/11/24 Voir plus > Voir moins >The high-energy behavior of N=4 SYM elastic amplitudes at strong coupling is studied by means of the AdS/CFT correspondence. For massless gluon-gluon scattering, we consider the amplitude found by Alday and Maldacena using a minimal surface in $AdS_5$ momentum space. For elastic scattering of massive quarks, we reconsider the eikonal method proposed by Janik and one of the authors of this paper, where the relevant minimal surface is a "generalized helicoid" in hyperbolic space ("Euclidean AdS_5"), from which the physical amplitude is obtained after an appropriate analytic continuation. Exploiting a conformal transformation, we are able to show that the quark-quark amplitude is dominated by the same cusp contribution already found in the gluon-gluon case. Both amplitudes are shown to be of Regge type at high energy, with the same logarithmic Regge trajectory, in agreement with the expected universality property of Regge amplitudes. The subleading constant term in the trajectory is known for gluon-gluon scattering, but it is regularization-scheme dependent. Hence, the full content of Regge universality remains an open problem. |
17/10/2011 | |

The growth rate of symplectic Floer homology M/11/23 Voir plus > Voir moins >The main theme of this paper is to study for a symplectomorphism of a compact surface, the asymptotic invariant which is defined to be the growth rate of the sequence of the total dimensions of symplectic Floer homologies of the iterates of the symplectomorphism. We prove that the asymptotic invariant coincides with asymptotic Nielsen number and with asymptotic absolute Lefschetz number. We also show that the asymptotic invariant coincides with the largest dilatation of the pseudo-Anosov components of the symplectomorphism and its logarithm coincides with the topological entropy. This implies that symplectic zeta function has a positive radius of convergence. |
14/09/2011 | |

Collapsing of Abelian Fibred Calabi-Yau Manifolds M/11/22 |
04/08/2011 | |

Topos co-évanescents et généralisations M/11/20 Voir plus > Voir moins >Cet article est consacré à l'étude d'un topos introduit par Faltings pour les besoins de la théorie de Hodge $p$-adique. Nous en présentons une nouvelle approche basée sur une généralisation des topos co-évanescents de Deligne. Chemin faisant, nous corrigeons la définition originelle de Faltings. This article is devoted to studying a topos introduced by Faltings for the purpose of $p$-adic Hodge theory. We present a new approach based on a generalisation of Deligne's co-vanishing topos. Along the way, we correct Faltings' original definition. |
13/07/2011 | |

On the double zeta values M/11/21 |
13/07/2011 | |

Surjectivity and equidistribution of the word $x^ay^b$ on $PSL(2,q)$ and $SL(2,q)$ M/11/19 Voir plus > Voir moins >We determine the positive integers a,b and the prime powers q for which the word map w(x,y)=x^ay^b is surjective on the group PSL(2,q) (and SL(2,q)). We moreover show that this map is almost equidistributed for the family of groups PSL(2,q) (and SL(2,q)). Our proof is based on the investigation of the trace map of positive words. |
29/06/2011 | |

From Traditional Set Theory -- that of Cantor, Hilbert, G\"odel, Cohen -- to Its Necessary Quantum Extension M/11/18 |
17/06/2011 | |

The vanishing volume of D=4 superspace P/11/14 |
07/06/2011 | |

Darboux coordinates, Yang-Yang functional, and gauge theory P/11/16 |
07/06/2011 | |

Tempered automorphic representations of the unitary group M/11/17 Voir plus > Voir moins >Following Arthur's study of the representations of the orthogonal and symplectic groups, we prove many cases of both the local and global Arthur conjectures for tempered representations of the unitary group. This completes the proof of Arthur's description of the discrete series representations of the quasi-split $p$-adic unitary group, and Arthur's description of the tempered discrete automorphic representations of the unitary group, satisfying certain technical conditions. |
04/06/2011 | |

How to take advantage of the blur between the finite and the infinite M/11/15 |
04/05/2011 | |

Derived equivalences for cluster-tilted algebras of Dynkin type D M/11/11 Voir plus > Voir moins >We provide a far reaching derived equivalence classification of cluster-tilted algebras of Dynkin type D. We introduce another notion of equivalence called good mutation equivalence which is slightly stronger than derived equivalence but is algorithmically more tractable, and give a complete classification together with normal forms. We also suggest normal forms for the derived equivalence classes, but some subtle questions in the derived equivalence classification remain open. |
28/04/2011 | |

Mutation classes of certain quivers with potentials as derived equivalence classes M/11/12 Voir plus > Voir moins >We characterize the marked bordered unpunctured oriented surfaces with the property that all the Jacobian algebras of the quivers with potentials arising from their triangulations are derived equivalent. These are either surfaces of genus g with b boundary components and one marked point on each component, or the disc with 4 or 5 points on its boundary. We show that for each such marked surface, all the quivers in the mutation class have the same number of arrows, and the corresponding Jacobian algebras constitute a complete derived equivalence class of finite-dimensional algebras whose members are connected by sequences of Brenner-Butler tilts. In addition, we provide explicit quivers for each of these classes. We consider also 10 of the 11 exceptional finite mutation classes of quivers not arising from triangulations of marked surfaces excluding the one of the quiver X_7, and show that all the finite-dimensional Jacobian algebras in such class (for suitable choice of potentials) are derived equivalent only for the classes of the quivers E_6^(1,1) and X_6. |
28/04/2011 | |

Which mutation classes of quivers have constant number of arrows? M/11/13 Voir plus > Voir moins >We classify the connected quivers with the property that all the quivers in their mutation class have the same number of arrows. These are the ones having at most two vertices, or the ones arising from triangulations of marked bordered oriented surfaces of two kinds: either surfaces with non-empty boundary having exactly one marked point on each boundary component and no punctures, or surfaces without boundary having exactly one puncture. This combinatorial property has also a representation-theoretic counterpart: to each such quiver there is a naturally associated potential such that the Jacobian algebras of all the QP in its mutation class are derived equivalent. |
28/04/2011 | |

Multiscale analysis of biological functions: the example of biofilms P/11/10 Voir plus > Voir moins >Biological functions involve processes at different scales. This statement is obviously true for organismic processes like development. It is already relevant for a bacterial colony, the example on which we shall more specifically focus here. Understanding biological functions thus requires to integrate knowledge and data of different natures, available at different levels, and described within different frameworks, from quantum mechanics (for elementary intracellular processes e.g. light transduction) to stochastic kinetics to deterministic rate equations and continuous medium theory (e.g. elasticity theory or hydrodynamics). Beyond the epistemic issue of capturing a real process in descriptions and measurements prescribed by our own abilities and limitations, biological functions and their regulation present a greater challenge: they are intrinsically and irreducibly multiscale processes. Indeed regulation of a biological function has to bridge the overall state of the cells as well as some surroundings features with the basic ingredients and mechanisms at the atomic or molecular scale, in an adaptive and interrelated way. A bacterial cell itself has to perform a multiscale integration. Accordingly our analysis and modeling should follow the same line. For these two main reasons, multiscale approaches play an essential role in the way towards the integrated understanding of biological functions, and all the more of biological systems. |
17/04/2011 | |

Configuration Space Renormalization of Massless QFT as an Extension Problem for Associate Homogeneous Distributions P/11/07 |
12/04/2011 | |

Quantum Einstein-Dirac Bianchi Universes P/11/08 |
12/04/2011 | |

Accurate numerical simulations of inspiralling binary neutron stars and their comparison with effective-one-body analytical models P/11/09 |
12/04/2011 | |

Absolute algebra III-the saturated spectrum M/11/06 |
15/03/2011 | |

Sur la correspondance de Simpson p-adique. I : étude locale M/11/05 Voir plus > Voir moins >Nous développons une nouvelle approche pour la correspondance de Simpson p-adique, intimement liée à l'approche originelle de Faltings, mais aussi inspirée du travail d'Ogus et Vologodsky sur un analogue en caractéristique p>0. Ce premier article est consacré aux aspects locaux de la théorie. \\ We develop a new approach for the p-adic Simpson correspondence, closely related to the original approach of Faltings, but also inspired by the work of Ogus and Vologodsky on an analogue in characteristic p>0. This first article is devoted to the local aspects of the theory. |
01/03/2011 | |

On Vassiliev invariants of braid groups of the sphere M/11/03 Voir plus > Voir moins >We construct a universal Vassiliev invariant for braid groups of the sphere and the mapping class groups of the sphere with $n$ punctures. The case of a sphere is different from the classical braid groups or braids of oriented surfaces of genus strictly greater than zero, since Vassiliev invariants in a group without 2-torsion do not distinguish elements of braid group of a sphere. |
31/01/2011 | |

Shannon entropy: a rigorous mathematical notion at the crossroads between probability, information theory, dynamical systems and statistical physics M/11/04 Voir plus > Voir moins >Statistical entropy was introduced by Shannon as a basic concept in information theory, measuring the average missing information on a random source. Extended into an entropy rate, it gives bounds in coding and compression theorems. I here present how statistical entropy and entropy rate relate to other notions of entropy, relevant either to probability theory (entropy of a discrete probability distribution measuring its unevenness), computer sciences (algorithmic complexity), the ergodic theory of dynamical systems (Kolmogorov-Sinai or metric entropy), or statistical physics (Boltzmann entropy). Their mathematical foundations and correlates (entropy concentration, Sanov, Shannon-McMillan-Breiman, Lempel-Ziv and Pesin theorems) clarify their interpretation and offer a rigorous basis to maximum entropy principles. Although often ignored, these mathematical perspectives give a central position to entropy and relative entropy in statistical laws describing generic collective behaviors. They provide insights into the notions of randomness, typicality and disorder. The relevance of entropy outside the realm of physics, for living systems and ecosystems, is yet to be demonstrated. |
31/01/2011 | |

On finite arithmetic groups M/11/02 Voir plus > Voir moins >In this paper we study representations of finite groups stable under Galois operation over arithmetic rings in local and global fields. |
21/01/2011 | |

On localization in holomorphic equivariant cohomology M/11/01 Voir plus > Voir moins >We study a holomorphic equivariant cohomology built out of the Atiyah algebroid of an equivariant holomorphic vector bundle and prove a related localization formula. localization formula. |
18/01/2011 | |

Statistical Properties of Cosmological Billiards P/10/16 |
16/12/2010 | |

On Effective Action of Multiple M5-branes and ABJM Action P/10/45 Voir plus > Voir moins >We calculate the fluctuations from the classical multiple M5-brane solution of ABJM action which we found in the previous paper. We obtain D4-brane-like action but the gauge coupling constant depends on the spacetime coordinate. This is consistent with the expected proporties of M5-brane action, although we will need to take into account the monopole operators in order to fully understand M5-branes. We also see that the Nambu-Poisson bracket is hidden in the solution. |
15/12/2010 | |

Cyclic structures in algebraic (co)homology theories M/10/44 Voir plus > Voir moins >This note discusses the cyclic cohomology of a left Hopf algebroid ($\times_A$-Hopf algebra) with coefficients in a right module-left comodule, defined using a straightforward generalisation of the original operators given by Connes and Moscovici for Hopf algebras. Lie-Rinehart homology is a special case of this theory. A generalisation of cyclic duality that makes sense for arbitrary para-cyclic objects yields a dual homology theory. The twisted cyclic homology of an associative algebra provides an example of this dual theory that uses coefficients that are not necessarily stable anti Yetter-Drinfel'd~modules. |
06/12/2010 | |

Generalized matrix models and AGT correspondence at all genera P/10/43 Voir plus > Voir moins >We study generalized matrix models corresponding to n-point Virasoro conformal blocks on Riemann surfaces with arbitrary genus g. Upon AGT correspondence, these describe four dimensional N=2 SU(2)^{n+3g-3} gauge theories with generalized quiver diagrams. We obtain the generalized matrix models from the perturbative evaluation of the Liouville correlation functions and verify the consistency of the description with respect to degenerations of the Riemann surface. Moreover, we derive the Seiberg-Witten curve for the $\CN=2$ gauge theory as the spectral curve of the generalized matrix model, thus providing a check of AGT correspondence at all genera. |
24/11/2010 | |

Incompressibility of generic orthogonal grassmannians M/10/42 |
23/11/2010 | |

A uniqueness theorem for meromorphic mappings with two families of hyperplanes M/10/41 Voir plus > Voir moins >In this paper, we extend the uniqueness theorem for meromorphic mappings to the case where the family of hyperplanes depends on the meromorphic mapping and where the meromorphic mappings may be degenerate. |
07/11/2010 | |

TENSOR STRUCTURE FROM SCALAR FEYNMAN MATROIDS P/10/40 Voir plus > Voir moins >We show how to interpret the scalar Feynman integrals which appear when reducing tensor integrals as scalar Feynman integrals coming from certain nice matroids. |
04/11/2010 | |

Precession effect of the gravitational self-force in a Schwarzschild spacetime and the effective one-body formalism P/10/37 |
27/10/2010 | |

Analytic modelling of tidal effects in the relativistic inspiral of binary neutron stars P/10/38 |
27/10/2010 | |

Accuracy and effectualness of closed-form, frequency-domain waveforms for non-spinning black hole binaries P/10/39 |
27/10/2010 | |

Open Gromov-Witten invariants and superpotentials for semi-Fano toric surfaces M/10/36 Voir plus > Voir moins >We compute the open Gromov-Witten invariants for every compact semi-Fano toric surface, i.e. a toric surface $X$ with nef anticanonical bundle. Unlike the Fano case, this involves non-trivial obstructions in the corresponding moduli problem. As an application, an explicit expression of the superpotential $W$ for the mirror of $X$ is obtained, which in turn gives an explicit ring presentation of the small quantum cohomology of $X$. We also give a computational verification of the natural ring isomorphism between the small quantum cohomology of $X$ and the Jacobian ring of $W$. |
25/10/2010 | |

The momentum kernel of gauge and gravity theories P/10/32 Voir plus > Voir moins >We derive an explicit formula for factorizing an n-point closed string amplitude into open string amplitudes. Our results are phrased in terms of a momentum kernel which in the limit of infinite string tension reduces to the corresponding field theory kernel. The same momentum kernel encodes the monodromy relations which lead to the minimal basis of color-ordered amplitudes in Yang-Mills theory. There are interesting consequences of the momentum kernel pertaining to soft limits of amplitudes. We also comment on surprising links between gravity and certain combinations of kinematic and color factors in gauge theory. |
20/10/2010 | |

Highly Transitive Actions of Out(Fn) M/10/35 Voir plus > Voir moins >An action of a group on a set is called k-transitive if it is transitive on ordered k-tuples and highly transitive if it is k-transitive for every k. We show that for n>3 the group Out(Fn) = Aut(Fn)/Inn(Fn) admits a faithful highly transitive action on a countable set. |
05/10/2010 | |

Seiberg-Witten curve via generalized matrix model P/10/34 Voir plus > Voir moins >We study the generalized matrix model which corresponds to the n-point toric Virasoro conformal block. This describes four-dimensional N=2 SU(2)^n gauge theory with circular quiver diagram by the AGT relation. We first verify that it is obtained from the perturbative calculation of the Liouville correlation function. We derive the Seiberg-Witten curve for N=2 gauge theory as a spectral curve of the generalized matrix model. |
28/09/2010 | |

Geometric analysis on small representations of GL(N,R) M/10/33 Voir plus > Voir moins >The most degenerate unitary principal series representations \pi_{i\lambda,\delta} (\lambda \in R, \delta \in Z/2 Z) of G = GL(N,R) attain the minimum of the Gelfand--Kirillov dimension among all irreducible unitary representations of G. This article gives an explicit formula of the irreducible decomposition of the restriction \pi_{i\lambda,\delta}|_H (\textit{branching law}) with respect to all symmetric pairs (G,H). For N=2n with n \ge 2, the restriction \pi_{i\lambda,\delta}|_H remains irreducible for H=Sp(n,R) if \lambda\ne0 and splits into two irreducible representations if \lambda=0. The branching law of the restriction \pi_{i\lambda,\delta}|_H is purely discrete for H = GL(n,C), consists only of continuous spectrum for H = GL(p,R) \times GL(q,R) (p+q=N), and contains both discrete and continuous spectra for H=O(p,q) (p>q \ge 1). Our emphasis is laid on geometric analysis, which arises from the restriction of `small representations' to various subgroups. |
27/09/2010 | |

On the Surjectivity of Engel Words on PSL(2,q) M/10/31 Voir plus > Voir moins >We investigate the surjectivity of the word map defined by the n-th Engel word on the groups PSL(2,q) and SL(2,q). For SL(2,q), we show that this map is surjective onto the subset SL(2,q)\{-id} provided that q>Q(n) is sufficiently large. Moreover, we give an estimate for Q(n). We also present examples demonstrating that this does not hold for all q. We conclude that the n-th Engel word map is surjective for the groups PSL(2,q) when q>Q(n). By using the computer, we sharpen this result and show that for any n<5, the corresponding map is surjective for all the groups PSL(2,q). This provides evidence for a conjecture of Shalev regarding Engel words in finite simple groups. In addition, we show that the n-th Engel word map is almost measure preserving for the family of groups PSL(2,q), with q odd, answering another question of Shalev. Our techniques are based on the method developed by Bandman, Grunewald and Kunyavskii for verbal dynamical systems in the group SL(2,q). |
23/09/2010 | |

a-Maximization in N=1 Supersymmetric Spin(10) Gauge Theories P/10/30 Voir plus > Voir moins >A summary is reported on our previous publications about four dimensional N=1 supersymmetric Spin(10) gauge theory with chiral superfields in the spinor and vector representations in the non-Abelian Coulomb phase. Carrying out the method of \amax, we exlpored decoupling operators in the infared and the renormalization flow of the theory. \ We also give a brief review on the non-Abelian Coulomb phase of the theory after recalling the unitarity bound and the a-maximization procedure in four-dimensional conformal field theory. This is a review article invited to International Journal of Modern Physics A. |
17/09/2010 | |

Topological invariants and moduli spaces of Gorenstein quasi-homogeneous surface singularities. M/10/29 Voir plus > Voir moins >We describe all connected components of the space of hyperbolic Gorenstein quasi-homogeneous surface singularities. We prove that any connected component is homeomorphic to a quotient of Rd by a discrete group. |
15/09/2010 | |

Restrictions of generalized Verma modules to symmetric pairs M/10/28 Voir plus > Voir moins >We initiate a new line of investigation on branching problems for generalized Verma modules with respect to reductive symmetric pairs (g, g'). In general, Verma modules may not contain any simple module when restricted to a reductive subalgebra. In this article we give a necessary and sufficient condition on the triple (g, g', p) such that the restriction X|_g' always contains simple g'-modules for any g-module X lying in the parabolic BGG category O^p attached to a parabolic subalgebra p of g. Formulas are derived for the Gelfand–Kirillov dimension of any simple module occurring in a simple generalized Verma module. We then prove that the restriction X|_g' is generically multiplicity-free for any p and any X\in O^p if and only if (g, g') is isomorphic to (A_n,A_n−1), (B_n,D_n), or (D_n+1,B_n). Explicit branching laws are also presented. |
26/08/2010 | |

Ramification and cleanliness M/10/27 Voir plus > Voir moins >This article is devoted to studying the ramification of Galois torsors and of $\ell$-adic sheaves in characteristic $p>0$ (with $\ell\not=p$). Let $k$ be a perfect field of characteristic $p>0$, $X$ be a smooth, separated and quasi-compact $k$-scheme, $D$ be a simple normal crossing divisor on $X$, $U=X-D$, $\Lambda$ be a finite local ${\mathbb Z}_\ell$-algebra, $F$ be a locally constant constructible sheaf of $\Lambda$-modules on $U$. We introduce a boundedness condition on the ramification of $F$ along $D$, and study its main properties, in particular, some specialization properties that lead to the fundamental notion of cleanliness and to the definition of the characteristic cycle of $F$. The cleanliness condition extends the one introduced by Kato for rank one sheaves. Roughly speaking, it means that the ramification of $F$ along $D$ is controlled by its ramification at the generic points of $D$. Under this condition, we propose a conjectural Riemann-Roch type formula for $F$. Some cases of this formula have been previously proved by Kato and by the second author (T.S.). |
23/08/2010 | |

Noncommutative Toda Chains, Hankel quasideterminants and Painlev\'e II equation M/10/25 Voir plus > Voir moins >We construct solutions of an infinite Toda system and an analogue of Painlev'e II equation over noncommutative differential division rings in terms of quasideterminants of Hankel matrices. |
27/07/2010 | |

Global Stringy Orbifold Cohomology, K-theory and de Rham Theory M/10/26 Voir plus > Voir moins >There are two approaches to constructing stringy multiplications for global quotients. The first one is given by first pulling back and then pushing forward. This has been used to define a global stringy extension of the functors $K_0,K^{top}, A^*,H^*$. The second one is given by first pushing forward and then pulling back. This has been used in the cyclic case and in particular for singularities with symmetries and for symmetric products. For Abelian quotients Chen and Hudiscussed such a construction in the de Rham setting. We give a rigorous formulation of de Rham theory for any global quotient from both points of view. We also show that the pull--push formalism has a solution by the push--pull equationsin the setting of cyclictwisted sectors. In the general case, we introduce ring extensions that allow us to treat all the stringy multiplications mentioned above. The first extension provides formal sections and a second extension fractional Euler classes. The formal sections allow us to give a pull-push solution while fractional Euler classes give a trivialization of the co--cycles of the pull-push formalism using the presentation of the obstruction bundle of Jarvis--Kaufmann--Kimura This trivialization can be interpreted as defining twist fields. We end with an outlook on applications to singularities with symmetries aka. orbifold Landau--Ginzburg models. |
27/07/2010 | |

Phenomenology of the Equivalence Principle with Light Scalars P/10/23 |
22/07/2010 | |

Equivalence Principle Violations and Couplings of a Light Dilaton P/10/24 |
22/07/2010 | |

Categorification of the Jones-Wenzl Projectors M/10/22 Voir plus > Voir moins >The Jones-Wenzl projectors play a central role in quantum topology, underlying the construction of SU(2) topological quantum field theories and quantum spin networks. We construct chain complexes, whose graded Euler characteristic is the ``classical''projector in the Temperley-Lieb algebra.We show that the projectors are homotopy idempotents and uniquely defined up to homotopy. Our results fit within the general framework of Khovanov's categorification of the Jones polynomial. Consequences of our construction include families of knot invariants corresponding to higher representations of quantum su(2), and a categorification of quantum spin networks. We introduce 6j-symbols in this context. |
14/07/2010 | |

FEYNMAN AMPLITUDES AND LANDAU SINGULARITIES FOR 1-LOOP GRAPHS M/10/20 Voir plus > Voir moins >We use mixed Hodge structures to investigate Feynman amplitudes as functions of external momenta and masses. |
02/07/2010 | |

Algebraic Structures in local QFT P/10/21 Voir plus > Voir moins >A review of the Hodge and Hopf-algebraic approach to QFT. |
02/07/2010 | |

Instantons on Gravitons P/10/19 Voir plus > Voir moins >Yang-Mills instantons on ALE gravitational instantons were constructed by Kronheimer and Nakajima in terms of matrices satisfying algebraic equations. These were conveniently organized into a quiver. We construct generic Yang-Mills instantons on ALF gravitational instantons. Our data is formulated in terms of matrix-valued functions of a single variable, that are organized into a bow. We introduce the general notion of a bow, its representation, its associated data and moduli space of solutions.The Nahm transform maps any bow solution to an instanton on an ALF space. We demonstrate that this map respects all complex structures on the moduli spaces, so it is likely to be an isometry, and use this fact to study the asymptotics of the moduli spacesof instantons on ALF spaces. |
23/06/2010 | |

Remarks on some locally Qp-analytic representations of GL2(F) in the crystalline case M/10/18 |
01/06/2010 | |

The emerging p-adic Langlands programme M/10/17 |
20/05/2010 | |

Classical analog of quantum Schwarzschild black hole: local vs global, and the mystery of log 3 P/10/15 Voir plus > Voir moins >The model is built in which the main global properties of classical and quasi-classical black holes become local. These are the event horizon, no-hair, temperature and entropy. Our construction is based on the features of a quantum collapse, discovered when studying some quantum black hole models. But our model is purely classical, and this allows to use selfconsistently the Einstein equations and classical (local) thermodynamics and explain in this way the log 3-puzzle. |
20/04/2010 | |

A Non-differentiable Noether's theorem M/10/14 Voir plus > Voir moins >In the framework of the non-differentiable embedding of Lagrangian systems, defined by Cresson and Greff, we prove a Noether's theorem based on the lifting of one-parameter groups of diffeomorphisms. |
14/04/2010 | |

The critical ultraviolet behaviour of N=8 supergravity amplitudes P/10/13 |
09/04/2010 | |

Eisenstein series for higher-rank groups and string theory amplitudes P/10/10 |
06/04/2010 | |

Kramers-Wannier Duality for Non-Abelian Lattice Spin Systems and Hecke Surfaces M/10/12 Voir plus > Voir moins >We discuss two themes: 1.Duality transformation for generalized Potts models and Hecke surfaces and $K$-regular graphs |
01/04/2010 | |

Pseudogroupes de Lie et théorie de Galois différentielle M/10/11 |
26/03/2010 | |

Intersecting D4-branes Model of Holographic QCD and Tachyon Condensation P/10/09 Voir plus > Voir moins >We consider the intersecting D4-brane and anti-D4-brane model of holographic QCD, motivated by the model that has recently been suggested by Van Raamsdonk and Whyte. We analyze such D4-branes by the use of the tachyonic Dirac-Born-Infeld action, so that we find the classical solutions describing the intersecting D4-branes and the U-shaped D4-branes. We show that the bi-fundamental ``tachyon'' field in the bulk theory provides a current quark mass and a quark condensate to the dual gauge theory and thatthe lowest modes of mesons obtain mass via tachyon condensation. Then evaluating the properties of a pion, one can reproduce Gell-Mann-Oakes-Renner relation. |
15/03/2010 | |

Monodromy and Jacobi-like Relations for Color-Ordered Amplitudes P/10/08 Voir plus > Voir moins >We discuss monodromy relations between different color-ordered amplitudes in gauge theories. We show that Jacobi-like relations of Bern, Carrasco and Johansson can be introduced in a manner that is compatible with these monodromy relations. The Jacobi-like relations are not the most general set of equations that satisfy this criterion. Applications to supergravity amplitudes follow straightforwardly through the KLT-relations. We explicitly show how the tree-level relations give rise to non-trivialidentities at loop level. |
12/03/2010 | |

Monodromy and Kawai-Lewellen-Tye Relations for Gravity Amplitudes P/10/07 |
08/03/2010 | |

A matrix model for the topological string I: deriving the matrix model P/10/06 |
04/03/2010 | |

String theory dualities and supergravity divergences P/10/05 |
22/02/2010 | |

Single-Lifting Macaulay-Type Formulae of Generalized Unmixed Toric Resultants M/10/04 |
28/01/2010 | |

Minimal representations and reductive dual pairs in conformal field theory P/10/03 |
15/01/2010 | |

Automorphic properties of low energy string amplitudes in various dimensions P/10/01 |
14/01/2010 | |

On the ultraviolet behaviour of N=8 supergravity amplitudes P/10/02 |
14/01/2010 | |

Sugawara-type constraints in hyperbolic coset models P/09/47 |
22/12/2009 | |

$E_{7(7)}$ invariant Lagrangian of $d=4$ ${\mathcal N} = 8$ supergravity P/09/52 |
22/12/2009 | |

Crystal melting on toric surfaces P/09/53 |
02/12/2009 | |

Almost etale resolution of foliations M/09/51 |
25/11/2009 | |

La cosmologie: un laboratoire pour la théorie des cordes P/09/50 |
17/11/2009 | |

Gravitational Self Force in a Schwarzschild Background and the Effective One Body Formalism P/09/49 |
03/11/2009 | |

Improved resummation of post-Newtonian multipolar waveforms from circularized compact binaries P/09/48 |
03/11/2009 | |

Sur un problème de compatibilité local-global modulo p pour GL2 M/09/46 |
05/10/2009 | |

Three \'Etudes in QFT P/09/45 |
23/09/2009 | |

Construire un noyau de la fonctorialité~? \\ Le cas de l'induction automorphe \\ sans ramification de ${\rm GL}_1$ à ${\rm GL}_2$ M/09/42 Voir plus > Voir moins >Le but de cet article (à paraître aux Annales de l'Institut Fourier) est de présenter une nouvelle méthode purement adélique pour réaliser le principe de fonctorialité de Langlands dans le cas de l'induction automorphe sans ramification de GL(1) à GL(2) sur les corps de fonctions. On construit sur le produit des groupes adéliques GL(1) et GL(2) un noyau de la fonctorialité. C’est une version « en famille » et locale de la construction par les modèles de Whittaker globaux, utilisée classiquement dans les « théorèmes réciproques » de Weil et Piatetski-Shapiro. La plus grande partie de la construction et des vérifications nécessaires est locale, c’est-à-dire se fait place par place. Il s’agit de prouver que deux fonctions, dont chacune est définie localement, deviennent égales après sommation sur les éléments rationnels de certains groupes. Cela résulte de la formule de Poisson, sur le modèle de la thèse de Tate, dès lors que l’on comprend comment nos deux fonctions se déduisent localement l’une de l’autre par une certaine transformation de Fourier. |
18/09/2009 | |

Construire des noyaux de la fonctorialité~? \\ Définition générale, \\ cas de l'identité de ${\rm GL}_2$ \\ et construction générale conjecturale \\ de leurs coefficients de Fourier M/09/43 |
18/09/2009 | |

``We are all your students, Mr. Cartan'' M/09/44 |
18/09/2009 | |

Notes sur l'histoire et la philosophie des mathématiques V : le problème de l'espace M/09/41 |
16/09/2009 | |

Noncommutative $\mathbf{K}$-correspondence categories, simplicial sets and pro $C^*$-algebras M/09/40 |
28/08/2009 | |

A representation-valued relative Riemann-Hurwitz theorem and the Hurwitz-Hodge bundle M/09/39 |
27/08/2009 | |

Non-renormalization conditions for four-gluon scattering in supersymmetric string and field theory P/09/35 |
20/08/2009 | |

Living in a contradictory world: categories vs sets? M/09/37 |
20/08/2009 | |

RENORMALIZATION AND RESOLUTION OF SINGULARITIES P/09/36 |
07/08/2009 | |

Two-Dimensional Topological Strings Revisited P/09/17 |
03/08/2009 | |

Minimal Basis for Gauge Theory Amplitudes P/09/33 |
15/07/2009 | |

Vinberg Algebras and Combinatorics M/09/34 Voir plus > Voir moins >Vinberg algebras are usually called pre-Lie algebras and were introduced long ago by Gerstenhaber. We propose to follow a diﬀerent route by motivating these algebras by problems coming from diﬀerential geometry, and ﬁrst studied in depth by Vinberg. We shall recall how the Lie bracket of vector ﬁelds can be obtained by skewsymmetriz- ing a more fundamental product. We shall then develop a combinatorial method for the higher order diﬀerential operators, quite similar to the procedure used in study- ing Runge–Kutta methods. We shall then move to nilpotent (or pronilpotent) Lie groups. In the last part of these lectures, I shall apply the previous methods in the renormalization theory of quantum ﬁelds (à la Connes–Kreimer). |
26/06/2009 | |

On the gravitational polarizability of black holes P/09/28 |
17/06/2009 | |

Fermionic Kac-Moody Billiards and Supergravity P/09/31 |
17/06/2009 | |

The Equivalence Principle and the Constants of Nature P/09/32 |
17/06/2009 | |

Supersymmetric Vacua and Bethe Ansatz P/09/09 |
16/06/2009 | |

The Effective One Body description of the Two-Body problem P/09/27 |
16/06/2009 | |

Relativistic tidal properties of neutron stars P/09/29 |
16/06/2009 | |

An improved analytical description of inspiralling and coalescing black-hole binaries P/09/30 |
16/06/2009 | |

Simplicity of Amplitudes in Gravity and Yang-Mills Theories P/09/26 |
15/06/2009 | |

Algebras for quantum fields P/09/24 Voir plus > Voir moins >We give an account of the current state of the approach to quantum field theory via Hopf algebras and Hochschild cohomology. We emphasize the versatility and mathematical foundation of this algebraic structure, and collect algebraic structures here inone place which are either scattered over the literature, or only implicit in previous writings. In particular we point out mathematical structures which can be helpful to farther develop our mathematical understanding of quantum fields. 1.1. |
09/06/2009 | |

The QCD $\beta$-function from global solutions to Dyson-Schwinger equations P/09/25 Voir plus > Voir moins >We study quantum chromodynamics from the viewpoint of untruncated Dyson–Schwinger equations turned to an ordinary differential equation for the gluon anomalous dimension. This nonlinear equation is parameterized by a function P(x) which is unknown beyond perturbation theory. Still, very mild assumptions on P(x) lead to stringent restrictions for possible solutions to Dyson– Schwinger equations. We establish that the theory must have asymptotic freedom beyond perturbation theory and alsoinvestigatethe low energy regime and the possibility for a mass gap in the asymptotically free theory. |
09/06/2009 | |

The Big Bang as the Ultimate Traffic Jam P/09/23 Voir plus > Voir moins >We present a novel solution to the nature and formation of the initial state of the Universe. It derives from the physics of a generally covariant extension of Matrix theory. We focus on the dynamical state space of this background independent quantum theory of gravity and matter, an infinite dimensional, complex non-linear Grassmannian. When this space is endowed with a Fubini–Study-like metric, the associated geodesic distance between any two of its points is zero. This striking mathematical result translates into a physical description of a hot, zero entropy Big Bang. The latter is then seen as a far from equilibrium, large fluctuation driven, metastable ordered transition, a “freezing by heating” jamming transition. Moreover, the subsequent unjamming transition could provide a mechanism for inflation while rejamming may model a Big Crunch, the final state of gravitational collapse. |
18/05/2009 | |

Surprising simplicity of N=8 supergravity P/09/22 |
15/05/2009 | |

An infinite family of solvable and integrable quantum systems on a plane P/09/21 Voir plus > Voir moins >An infinite family of exactly-solvable and integrable potentials on a plane is introduced. It is shown that all already known rational potentials with the above properties allowing separation of variables in polar coordinates are particular cases of thisfamily. The underlying algebraic structure of the new potentials is revealed as well as its hidden algebra. We conjecture that all members of the family are also superintegrable and demonstrate this for the first few cases. A quasi-exactly-solvableand integrable generalization of the family is found. |
13/05/2009 | |

Quantum Groups and Braid Group Statistics in Conformal Current Algebra Models P/09/18 |
24/04/2009 | |

Two kinds of derived categories, Koszul duality, and comodule-contramodule correspondence M/09/20 Voir plus > Voir moins >We discuss derived categories of the first kind for DG-modules, DG-comodules, and DG-contramodules, derived categories of the second kind for CDG-modules, CDG-comodules, and CDG-contramodules. For the latter two, the comodule-contramodule correspondence is constructed. Nonhomogeneous Koszul duality (equivalence of exotic derived categories) is obtained in conilpotent and nonconilpotent versions. A_\infty structures are also considered. |
24/04/2009 | |

Generalised Kostka-Foulkes polynomials and cohomology of line bundles on homogeneous vector bundles M/09/19 |
23/04/2009 | |

Sutherland-type Trigonometric Models, Trigonometric Invariants and Multivariable Polynomials. II. $E_7$ case P/09/15 |
08/04/2009 | |

Discrete Minimal Surface Algebras M/09/14 Voir plus > Voir moins >We consider Discrete Minimal Surface Algebras (DMSA) as noncommutative analogues of minimal surfaces in higher dimensional spheres. These algebras appear naturally in the context of Membrane Theory, where sequences of their representations are used as a regularization of the theory. After showing that the defining relations of the algebra are consistent, and that one can compute a basis of the universal enveloping algebra, we give several explicit examples of DMSAs in terms of subsets of sl(n) (any semi-simple Lie algebra providing a trivial example by itself). A special class of DMSAs are Yang-Mills algebras. The representation graph is introduced to study representations of DMSAs of dimension d<=4, and properties of representations are related to properties of graphs. The representation graph of a tensor product is (generically) the Cartesian product of the corresponding graphs. We provide explicit examples of irreducible representations and, for coinciding eigenvalues, classify all the unitary representations of the corresponding algebras. |
27/03/2009 | |

Higher-loop amplitudes in the non-minimal pure spinor formalism P/09/13 |
23/03/2009 | |

Recursive relations in the core Hopf algebra P/09/12 Voir plus > Voir moins >We study co-ideals in the core Hopf algebra underlying a quantum field theory. |
17/03/2009 | |

Integrable Systems in Noncommutative Spaces P/09/11 Voir plus > Voir moins >We discuss extension of soliton theories and integrable systems into non-commutative (NC) spaces. In the framework of NC integrable hierarchy, we give infinite conserved quantities and exact soliton solutions for many NC integrable equations,which are represented in terms of Strachan's products and quasi-determinants, respectively. We also present a relation to an NC Anti-Self-Dual Yang-Mills equation, and make comments on how ``integrability'' should be considered in noncommutative spaces. |
13/03/2009 | |

Scattering Amplitudes and BCFW Recursion in Twistor Space P/09/10 Voir plus > Voir moins >A number of recent advances in our understanding of scattering amplitudes have been inspired by ideas from twistor theory. While there has been much work studying the twistor space support of scattering amplitudes, this has largely been done by examiningthe amplitudes in momentum space. In this paper, we construct the actual twistor scattering amplitudes themselves. The main reasons for doing so are to seek a formulation of scattering amplitudes in N=4 super Yang-Mills in which superconformal symmetry ismanifest, and to use the progress in on-shell methods in momentum space to build our understanding of how to construct quantum field theory in twistor space. We show that the recursion relations of Britto, Cachazo, Feng and Witten have a natural twistorformulation that, together with the three-point seed amplitudes, allow us in principle to recursively construct general tree amplitudes in twistor space. The twistor space BCFW recursion is tractable, and we obtain explicit formulae for n-particle MHV and NMHV amplitudes, together with their CPT conjugates (whose representations are distinct in our chiral framework). The amplitudes are a set of purely geometric, superconformally invariant delta functions, dressed by certain sign operators. These sign operators subtly violate conformal invariance, even for tree-level amplitudes in N=4 super Yang-Mills, and we trace their origin to a topological property of split signature spacetime. Our work is related via a twistor transform to the ambidextrous twistor diagram approach of Hodges and of Arkani-Hamed, Cachazo, Cheung and Kaplan. |
12/03/2009 | |

An accurate few-parameter ground state wave function for the Lithium atom P/09/08 |
25/02/2009 | |

On two-dimensional quantum gravity and quasiclassical integrable hierarchies P/09/06 |
24/02/2009 | |

Essential hyperbolic Coxeter polytopes M/09/07 Voir plus > Voir moins >We introduce a notion of essential hyperbolic Coxeter polytope as a polytope which fits some minimality conditions. The problem of classification of hyperbolic reflection groups can be easily reduced to classification of essential Coxeter polytopes. We determine a potentially large combinatorial class of polytopes containing, in particular, all the compact hyperbolic Coxeter polytopes of dimension at least $6$ which are known to be essential, and prove that this class contains finitely many polytopes only. We also construct an effective algorithm of classifying polytopes from this class, and realize it in four-dimensional case. |
24/02/2009 | |

The core Hopf algebra P/09/05 Voir plus > Voir moins >We study the core Hopf algebra underlying the renormalization Hopf algebra. |
13/02/2009 | |

On a class of hamiltonian fiber bundles M/09/04 Voir plus > Voir moins >We study an interesting class of hamiltonian fiber bundles whose fibers are compact homogeneous symplectic manifolds. Applications to the cohomology of their symplectomorphism group are given. |
04/02/2009 | |

Exploiting N=2 in consistent coset reductions of type IIA P/09/03 |
27/01/2009 | |

Generalized E(7(7)) coset dynamics and D=11 supergravity P/09/02 Voir plus > Voir moins >The hidden on-shell E(7(7)) symmetry of maximal supergravity is usually discussed in a truncation from D=11 to four dimensions. In this article, we reverse the logic and start from a theory with manifest off-shell E(7(7)) symmetry inspired by West's coset construction. Following de Wit's and Nicolai's idea that a 4+56 dimensional ``exceptional geometry'' underlies maximal supergravity, we construct the corresponding Lagrangian and the supersymmetry variations for the 56 dimensional subsector. We prove that both the dynamics and the supersymmetry coincide with D=11 supergravity in a truncation to d=7 in the expected way. |
11/01/2009 | |

Un pays dont on ne connaîtrait que le nom (Grothendieck et les 'motifs') M/09/01 |
08/01/2009 | |

Topological String on ${\mathcal S}^2$ Revisited P/08/18 |
31/12/2008 | |

Théories de Galois géométriques M/08/62 Voir plus > Voir moins >Nous présentons de manière conceptuelle les idées de Riemann sur les singularités et la monodromie, et nous l'illustrons par l'étude des fonctions algébriques, et des solutions des équations différentielles. Cela fournit une approche unifiée aux diverses théories de Galois. |
29/12/2008 | |

Yet Another Poincaré's Polyhedron Theorem M/08/64 Voir plus > Voir moins >This work contains a new version of Poincare's Polyhedron Theorem that also suits geometries of nonconstant curvature lacking concepts of convexity. Most conditions of the theorem, being as local as possible, are easy to verify in practice. |
22/12/2008 | |

Notion de spectre M/08/61 Voir plus > Voir moins >La notion de spectre est au départ une notion physique. Elle a pris progressivement une signification de plus en plus large en mathématique, sa signification mathématique la plus importante lui ayant été donnée par Grothendieck dans sa théorie des schémas. Nous nous promènerons donc de la physique à la géométrie algébrique. |
19/12/2008 | |

Entropy estimation of symbolic sequences: How short is a short sequence? P/08/63 Voir plus > Voir moins >While entropy per unit time is a meaningful index to quantify the dynamic features of experimental time series, its estimation is often hampered by the finite length of the data. We here investigate the performance of entropy estimation procedures, relying either on block entropies or Lempel-Ziv complexity, when only {\it very short symbolic sequences} are available. Heuristic analytical arguments point at the influence of temporal correlations on the bias and statistical fluctuations, and put forward a reduced effective sequence length suitable for error estimation. Numerical studies are conducted using, as benchmarks, the wealth of different dynamic regimes generated by the family of logistic maps and stochastic evolutions generated by a Markov chain of tunable correlation time. Practical guidelines and validity criteria are proposed, based on the result that the quality of entropy estimation is sensitive to the sequence temporal correlation hence self-consistently depends on the entropy value itself. |
19/12/2008 | |

Quantum Integrability and Supersymmetric Vacua P/08/59 |
02/12/2008 | |

Phase space polarization and the topological string: a case study P/08/60 |
02/12/2008 | |

Instanton Partition Functions and M-Theory P/08/16 |
27/11/2008 | |

About Time P/08/58 |
24/11/2008 | |

Simplicity in the Structure of QED and Gravity Amplitudes P/08/54 |
21/11/2008 | |

Dimensional Regularization of the Gravitational Interaction of Point Masses in the ADM Formalism P/08/55 |
21/11/2008 | |

What is Missing from Minkowski s Raum und Zeit Lecture P/08/56 |
21/11/2008 | |

Improved Resummation of Post-Newtonian Multipolar Waveforms from Circularized Compact Binaries P/08/57 |
21/11/2008 | |

Two Dimensional Topological Strings and Gauge Theory P/08/17 |
18/11/2008 | |

Multi-valued hyperelliptic continued fractions of generalized Halphen type M/08/53 Voir plus > Voir moins >We introduce and study higher genera generalizations of the Halphen theory of continued fractions. The basic notion we start with is hyperel- liptic Halphen (HH) element p X2g+2 ¡ p Y2g+2 x ¡ y ; depending on parameter y, where X2g+2 is a polynomial of degree 2g + 2 and Y2g+2 = X2g+2(y). We study regular and irregular HH elements, their continued fraction developments and some basic properties of such developments such as: even and odd symmetry and periodicity. There is a 2 $ g + 1 dynamics which lies in the basis of the developed continued fractions theory. We give two geometric realizations of this dynamics. The ¯rst one deals with nets of polynomials and with polygons circumscribed about a conic K. The dynamics is realized as a path ofpolygons of g + 1 sides inscribed in a curve B of degree 2g and circumscribed about the conic K obtained by successive moves, so called { °ips along edges. The second geometric realization leads to a new interpretation of generalized Jacobians of hyperelliptic curves. 1 |
18/11/2008 | |

Partition Functions of Matrix Models as the First Special Functions of String Theory II. Kontsevich Model P/08/52 |
07/11/2008 | |

Diagrammes de Diamond et $(\varphi,\Gamma)$-modules M/08/51 |
23/09/2008 | |

Piecewise principal comodule algebras M/08/50 Voir plus > Voir moins >A comodule algebra P over a Hopf algebra H with bijective antipode is called principal if the coaction of H is Galois and P is H-equivariantly projective (faithfully flat) over the coaction-invariant subalgebra B. We prove that principality is a piecewise property: given N comodule-algebra surjections P -> P_i whose kernels intersect to zero, P is principal if and only if all P_i's are principal. Furthermore, assuming the principality of P, we show that the lattice these kernels generate is distributive if and only if so is the lattice obtained by intersection with B. Finally, assuming the above distributivity property, we obtain a flabby sheaf of principal comodule algebras over a certain space that is universal for all such N-families of surjections P -> P_i and such that the comodule algebra of global sections is P. |
26/08/2008 | |

Tamagawa defect of Euler systems M/08/48 Voir plus > Voir moins >As remarked by Mazur an Rubin (2004, {\em Mem. Amer. Math. Soc.\/}, 168(799)) one does not expect the Kolyvagin system obtained from an Euler system for a $p$-adic Galois representation $T$ to be \emph{primitive} (in the sense of \emph{loc. cit.}) if$p$ divides a Tamagawa number at a prime $\ell\neq p$; thus fails to compute the correct size of the relevant Selmer module. In this paper we obtain a lower bound for the size of the cokernel of the Euler system to Kolyvagin system map in terms of the local Tamagawa numbers of $T$, refining a result of \emph{loc. cit.}. We show how this partially accounts for the missing Tamagawa factors in Kato's calculations with his Euler system. |
19/08/2008 | |

Stickelberger elements and Kolyvagin systems M/08/49 Voir plus > Voir moins >In this paper we construct (many) Kolyvagin systems out of Stickelberger elements, utilizing ideas borrowed from our previous work on Kolyvagin systems of Stark elements. We show how to apply this construction to prove results on the \emph{odd} parts ofthe ideal class groups of CM fields which are abelian over a totally real field, and deduce the main conjecture of Iwasawa theory for totally real fields (for totally odd characters). Although the main results of this paper have already been established by Wiles, our approach provides another example (which slightly differs from the case of Stark elements) on how to study \emph{Kolyvagin systems of core rank $r>1$} (in the sense of Mazur and Rubin). The analogous (and in some sense complementary) results for \emph{even} parts of the ideal class groups and main conjectures for totally even characters of totally real number fields have been previously obtained by the author using similar ideas. |
19/08/2008 | |

Analytic subvarieties with many rational points M/08/46 |
30/07/2008 | |

Dyson's Theorem for curves M/08/47 |
30/07/2008 | |

Vertex algebroids over Veronese rings M/08/45 Voir plus > Voir moins >We find a canonical quantization of Courant algebroids over Veronese rings. Part of our approach allows a semi-infinite cohomology interpretation, and the latter can be used to define sheaves of chiral differential operators on some homogeneous spaces including the space of pure spinors punctured at a point. |
29/07/2008 | |

LOCAL STABILITY OF A QUASI-LINEAR AGE-SIZE STRUCTURED POPULATION DYNAMICS MODEL M/08/44 Voir plus > Voir moins >The local stability of a quasi-linear age-size structured population model studied in Tchuenche (2007) is analysed. If a certain threshold parameter known as the basic reproductive rate is less than unity, then the trivial steady state is locally asymptotically stable. Also, it is shown that if the only real root of the equation ${\cal R}(m')=1$ is negative, then, the non trivial steady state is locally exponentially asymptotically stable. |
03/07/2008 | |

Pure Spinor Partition Function and the Massive Superstring Spectrum P/08/31 |
03/07/2008 | |

One-loop $\beta$ functions of a translation-invariant renormalizable noncommutative scalar model P/08/43 Voir plus > Voir moins >Recently, a new type of renormalizable $\phi^{\star 4}_{4}$ scalar model on the Moyal space was proved to be perturbatively renormalizable. It is translation-invariant and introduces in the action a $a/(\theta^2p^2)$ term. We calculate here the$\beta$ and $\gamma$ functions at one-loop level for this model. The coupling constant $\beta_\lambda$ function is proved to have the same behaviour as the one of the $\phi^4$ model on the commutative $\mathbb{R}^4$. The $\beta_a$ function of the new parameter $a$ is also calculated. Some interpretation of these results are done. |
24/06/2008 | |

SELF-SIMILAR P-ADIC FRACTAL STRINGS AND THEIR COMPLEX DIMENSIONS M/08/42 Voir plus > Voir moins >We develop a geometric theory of self-similar p-adic fractal strings and their complex dimensions. We obtain a closed-form formula for the geo- metric zeta functions and show that these zeta functions are rational functions in an appropriate variable. We also prove that every self-similar p-adic fractal string is lattice. Finally, we deﬁne the notion of a nonarchimedean self-similar set and discuss its relationship with that of a self-similar p-adic fractal string. We illustrate the general theory by two simple examples, the nonarchimedean Cantor and Fibonacci strings. |
11/06/2008 | |

Regularization, renormalization, and renormalization groups: relationships and epistemological aspects P/08/41 Voir plus > Voir moins >This paper confronts renormalization used in quantum field theory and that used in critical phenomena studies in statistical mechanics or dynamical systems theory. Regularization that cures spurious divergences is distinguished from renormalization transformations allowing to compute actual physical divergences. The former generates a group, and is also encountered in singular perturbation analyses in nonlinear physics. The latter generates a semi-group, and is implemented as a flow in a space of models; its analysis, focusing on fixed points and their neighborhood, allows to determine asymptotic scaling behavior, to delineate universality classes and to assess model structural stability (or instability, i.e. crossovers). The renormalization group can be seen as a symmetry group and a general covariant formulation is proposed. Aspects presented here show that renormalization theory has emulated a shift of focus from the investigation of outcomes of a given model to the analysis of models themselves, by relating models of the same system at different scales or grouping models of different systems exhibiting the same large-scale behavior. So doing, not only (subjective and partial) models are distinguished from underlying physical systems, but also intrinsic physical features can be derived from model comparison and classification. |
10/06/2008 | |

Open-Closed Moduli Spaces and Related Algebraic Structures M/08/40 Voir plus > Voir moins >We set up a Batalin-Vilkovisky Quantum Master Equation (QME) for open-closed string theory and show that the corresponding moduli spaces give rise to a solution, a generating function for their fundamental chains. The equation encodes the topological structure of the compactification of the moduli space of bordered Riemann surfaces. The moduli spaces of bordered $J$-holomorphic curves are expected to satisfy the same equation, and from this viewpoint, our paper treats the case of the target space equal to a point. We also introduce the notion of a symmetric Open-Closed Topological Conformal Field Theory (OC TCFT) and study the L_infty and A_infty algebraic structures associated to it. |
06/06/2008 | |

A trace on fractal graphs and the Ihara zeta function M/08/36 Voir plus > Voir moins >Starting with Ihara's work in 1968, there has been a growing interest in the study of zeta functions of finite graphs, by Sunada, Hashimoto, Bass, Stark and Terras, Mizuno and Sato, to name just a few authors. Then, Clair and Mokhtari-Sharghi have studied zeta functions for infinite graphs acted upon by a discrete group of automorphisms. The main formula in all these treatments establishes a connection between the zeta function, originally defined as an infinite product, and the Laplacian of the graph. In this article, we consider a different class of infinite graphs. They are fractal graphs, i.e. they enjoy a self-similarity property. We define a zeta function for these graphs and, using the machinery of operator algebras, we prove a determinant formula, which relates the zeta function with the Laplacian of the graph. We also prove functional equations, and a formula which allows approximation of the zeta function by the zeta functions of finite subgraphs. |
29/05/2008 | |

Ihara's zeta function for periodic graphs and its approximation in the amenable case M/08/37 Voir plus > Voir moins >In this paper, we give a more direct proof of the results by Clair and Mokhtari-Sharghi on the zeta functions of periodic graphs. In particular, using appropriate operator-algebraic techniques, we establish a determinant formula in this context and examine its consequences for the Ihara zeta function. Moreover, we answer in the affirmative one of the questions raised in \cite{GrZu} by Grigorchuk and $\dot{\text{Z}}$uk. Accordingly, we show that the zeta function of a periodic graph with an amenable group action is the limit of the zeta functions of a suitable sequence of finite subgraphs. |
29/05/2008 | |

Bartholdi Zeta Functions for Periodic Simple Graphs M/08/38 Voir plus > Voir moins >The definition of the Bartholdi zeta function is extended to the case of infinite periodic graphs. By means of the analytic determinant for semifinite von~Neumann algebras studied by the authors in \cite{GILa03}, a determinant formula and functional equations are obtained for this zeta function. |
29/05/2008 | |

Ihara zeta functions for periodic simple graphs M/08/39 Voir plus > Voir moins >The definition and main properties of the Ihara zeta function for graphs are reviewed, focusing mainly on the case of periodic simple graphs. Moreover, we give a new proof of the associated determinant formula, based on the treatment developed by Stark and Terras for finite graphs. |
29/05/2008 | |

Toward zeta functions and Complex Dimensions of Multifractals M/08/34 Voir plus > Voir moins >Multifractals are inhomogeneous measures (or functions) which are typically described by a full spectrum of real dimensions, as opposed to a single real dimension. Results from the study of fractal strings in the analysis of their geometry, spectra and dynamics via certain zeta functions and their poles (the complex dimensions) are used in this text as a spring board to define similaar tools for the study of multifractals such as the binomial measure. The goal of this work is to shine light on new ideas and perspectives rather than to summarize a coherent theory. Progress has been made which connects these new perspectives to and expands upon classical results, leading to a healthy variety of natural and interesting questions for further investigation and elaboration. |
28/05/2008 | |

Turbulence and Holography P/08/35 |
28/05/2008 | |

Sutherland-type trigonometric models, trigonometric invariants, and multivariate polynomials P/08/32 |
16/05/2008 | |

The QED $\beta$-function from global solutions to Dyson-Schwinger equations P/08/33 Voir plus > Voir moins >We discuss the structure of beta functions as determined by the recursive nature of Dyson-Schwinger equations turned into an analysis of ordinary differential equations, with particular emphasis given to quantum electrodynamics. In particular we determine when a separatrix for solutions to such ODEs exists and clarify the existence of Landau poles beyond perturbation theory. Both are determined in terms of explicit conditions on the asymptotics for the growth of skeleton graphs. |
15/05/2008 | |

Tube Formulas and complex Dimensions of Self-Similar tilings M/08/27 Voir plus > Voir moins >We use the self-similar tilings constructed by Erin Pearse to define a generating function for the geometry of a self-similar set in Euclidean space. This geometric zeta function encodes scaling and curvature properties related to the complement of the fractal set, and the associated system of mappings. This allows one to obtain the complex dimensions of the self-similar tiling as the poles of the geometric zeta function and hence develop a tube formula for self-similar tilings in Rd. The resulting power series in epsilon is a fractal extension of Steiner's classical tube formula for convex bodies K of Rd. Our sum has coefficients related to the curvatures of the tiling, and contains terms for each integer i=0,1,...,d-1, just as Steiner's does. However, our formula also contains a term for each complex dimension. This provides further justification for the term ``complex dimension''. It also extends several aspects of the theory of fractal strings to higher dimensions and sheds new light on the tube formula for fractals strings obtained by Michel Lapidus and Machiel van Frankenhuisjen. |
02/05/2008 | |

Tube Formulas for Self-Similar Fractals M/08/28 Voir plus > Voir moins >Tube formulas (by which we mean an explicit formula for the volume of an (inner) epsilon-neighbourhood of a subset of a suitable metric space) have been used in many situations to study properties of the subset. For smooth submanifolds of Euclidean space, this includes Weyl's celebrated results on spectral asymptotics, and the subsequent relation between curvature and spectrum. Additionally, a tube formula contains information about the dimension and measurability of rough sets. In convex geometry, thetube formula of a convex subset of Euclidean space allows for the definition of certain curvature measures. These measures describe the curvature of sets which may be too irregular to support derivatives. In this survey paper, we describe some recent advances in the development of tube formulas for self-similar fractals, and their applications and connections to the other topics mentioned here. |
02/05/2008 | |

Nonarchimedean Cantor Set and String M/08/29 Voir plus > Voir moins >We construct a nonarchimedean (or p-adic) analogue of the classical ternary set C. In particular, we show that this nonarchimedean Cantor set C3 is self-similar. Furthermore, we characterize C3 as the subset of 3-adic integers whose elements contain only 0's and 2's in their 3-adic expansions and prove that C3 is naturally homeomorphic to C. Finally, from the point of view of fractal strings and their complex dimensions (see the books by Lapidus and van Frankhuijsen), the corresponding non archimedean Cantor string resembles the standard archimedean (or real) Cantor string perfectly. |
02/05/2008 | |

MIXED HODGE STRUCTURES AND RENORMALIZATION IN PHYSICS M/08/30 Voir plus > Voir moins >We relate renormalization in perturbative quantum field theory to the theory of limiting mixed Hodge structures using parametric representations of Feynman graphs. |
02/05/2008 | |

Recycling the Independent Field Approximation argument in the far field P/08/26 Voir plus > Voir moins >The Independent Field Approximation for the entropy production of Laplacian mild diﬀusional ﬁelds is rigorously introduced and discussed. Some new results due to super-convergent algorithms are presented and the meaning of the active zone concept is enlightened. |
23/04/2008 | |

On the origin of time and the Universe P/08/25 |
22/04/2008 | |

Fractal structure of the block-complexity function M/08/24 Voir plus > Voir moins >We demonstrate that the block-complexity function for words from 3-letter and 4-letter alphabets exhibits a fractal structure. The resulting fractals have dimensions approximately equal to 1.892 and 1.953 respectively. We visualize approximations of the corresponding fractals using sequences of length 6 and 5 respectively. We note that a similar fractal structure has been established recently for the block-complexity function for words from a 2-letter alphabet, using a diﬀerent terminology. In this case, the resulting fractal has dimension approximately equal to 1.584. |
18/04/2008 | |

Infinite Dimensional Lie Algebras in 4D Conformal Field Theory P/08/23 |
09/04/2008 | |

On a class of holonomic D-modules on symmetric matrices attached to the general linear group M/08/22 Voir plus > Voir moins >We give a classification of regular holonomic D-modules on complex symmetric matrices whose characteristic variety is the union of conormal bundles to the orbits of the general linear group |
02/04/2008 | |

Accurate Effective-One-Body waveforms of inspiralling and coalescing black-hole binaries P/08/21 |
01/04/2008 | |

SQCD: A Geometric Apercu P/08/04 Voir plus > Voir moins >We take new algebraic and geometric perspectives on the old subject of SQCD. We count chiral gauge invariant operators using generating functions, or Hilbert series, derived from the plethystic programme and the Molien-Weyl formula. Using the character expansion technique, we also see how the global symmetries are encoded in the generating functions. Equipped with these methods and techniques of algorithmic algebraic geometry, we obtain the character expansions for theories with arbitrary numbers of colours and flavours. Moreover, computational algebraic geometry allows us to systematically study the classical vacuum moduli space of SQCD and investigate such structures as its irreducible components, degree and syzygies. We find the vacuum manifolds of SQCD to be affine Calabi-Yau cones over weighted projective varieties. |
01/04/2008 | |

Groupoides de Lie et leurs alg\'ebroides M/08/20 Voir plus > Voir moins >Résumé : Ce texte d’un exposé prochain au Séminaire Bourbaki est une revue des notions de géométrie différentielle liées aux variétés symplectiques et de Poisson, aux groupoides de Lie et aux algébroides de Lie. Ces notions ont des liens multiples,et la correspondance groupoide de Lie $rightleftarrows$ algébroide de Lie généralise la correspondance bien connue groupe de Lie $rightleftarrows$ algèbre de Lie. Les groupoides de Lie jouent un rôle analogue aux champs algébriques et permettent, grâce à l’équivalence de Morita entre groupoides de Lie, de définir des variétés-quotients généralisées (par exemple, espace des feuilles d’un feuilletage). L’exposé s’achève par une présentation élémentaire de la théorie de Galois des équations différentielles (Picard-Vessiot-Ritt-Kolchin). Abstract: The purpose of this coming lecture at the Bourbaki Seminar is a review of a set of important notions in differential geometry: symplectic and Poisson varieties, Lie groupoids and Lie algebroids. All these notions are strongly connected and the classical correspondence Lie groups $rightleftarrows$ Lie algebras extends to a correspondence Lie groupoids $rightleftarrows$ Lie algebroids. One can considers Lie groupoids up to an equivalencemodelled after the Morita equivalence in algebra. They form the ob jects of a category, closely related to stacks in algebraic geometry, and representing generalized varieties like the space of leaves of a foliation. We end up with a new presentation of the differential Galois theory. |
25/03/2008 | |

Instantons beyond topological theory II P/08/15 |
25/03/2008 | |

On the conjecture of Kevin Walker M/08/19 Voir plus > Voir moins >In 1985 Kevin Walker in his study of topology of polygon spaces raised an interesting conjecture in the spirit of the well-known question "Can you hear the shape of a drum?" of Marc Kac. Roughly, Walker's conjecture asks if one can recover relativelengths of the bars of a linkage from intrinsic algebraic properties of the cohomology algebra of its configuration space. In this paper we prove that the conjecture is true for polygon spaces in the 3-dimensional space. We also prove that for planar polygon spaces the conjecture holds is several modified forms: (a) if one takes into account the action of a natural involution on cohomology, (b) if the cohomology algebra of the involution's orbit space is known, or (c) if the length vector is normal. Some of our results allow the length vector to be non-generic, the corresponding polygon spaces have singularities. Our main tool is the study of the natural involution and its action on cohomology. A crucial role in our proof plays the solution of the isomorphism problem for monoidal rings due to J. Gubeladze. |
21/03/2008 | |

Effective one body approach to the dynamics of two spinning black holes with next-to-leading order spin-orbit coupling P/08/14 |
11/03/2008 | |

String theory, gravity and experiment P/08/08 |
04/03/2008 | |

Introductory lectures on the Effective One Body formalism P/08/09 |
04/03/2008 | |

Faithful Effective One Body waveforms of equal-mass coalescing black-hole binaries P/08/10 |
04/03/2008 | |

Constraints on the variability of quark masses from nuclear binding P/08/11 |
04/03/2008 | |

Comparing Effective One Body gravitational waveforms to accurate numerical data P/08/12 |
04/03/2008 | |

Hamiltonian of two spinning compact bodies with next-to-leading order gravitational spin-orbit coupling P/08/13 |
04/03/2008 | |

On the Brownian gas: a field theory with a Poissonian ground state P/08/05 Voir plus > Voir moins >As a first step towards a successful field theory of Brownian particles in interaction, we study exactly the non-interacting case, its combinatorics and its nonlinear time-reversal symmetry. Even though the particles do not interact, the field theory contains an interaction term: the vertex is the hallmark of the original particle nature of the gas and it enforces the constraint of a strictly positive density field, as opposed to a Gaussian free field. We compute exactly all the n-point density correlation functions, determine non-perturbatively the Poissonian nature of the ground state and emphasize the futility of any coarse-graining assumption for the derivation of the field theory. We finally verify explicitly, on the n-point functions, the fluctuation-dissipation theorem implied by the time-reversal symmetry of the action. |
27/02/2008 | |

NOT SO NON-RENORMALIZABLE GRAVITY P/08/06 Voir plus > Voir moins >We review recent ideas [1] how gravity might turn out to be a renormalizable theory after all. |
27/02/2008 | |

Quantum Groups and Braid Group Statistics in Conformal Field Theory P/08/07 Voir plus > Voir moins >A quantum universal enveloping algebra $U_q$ and the braid group on $n$ strands ${\mathcal B}_n$ mutually commute when acting on the $n$-fold tensor product of a $U_q$-module. Their combined action is applied to low dimensional systems -- the only ones that admit a nontrivial monodromy and hence a braid group (rather than a permutation group) statistics. The lectures introduce the notions of braid group and Hopf algebra and apply them to examples of 2-dimensional (rational) conformal field theory. The case of the $su(2)$ current algebra model, for which the deformation parameter $q$ is an even root of unity, is considered in some detail. In particular, the solution to the Schwarz problem for the $su(2)$ Knizhnik-Zamolodchikov equation is reviewed. |
27/02/2008 | |

Classical and quantum integrability M/08/03 |
15/02/2008 | |

Twistor Strings, Gauge Theory and Gravity P/08/02 |
06/02/2008 | |

Cofiniteness conditions, projective covers and the logarithmic tensor product theory M/08/01 Voir plus > Voir moins >We construct projective covers of irreducible V-modules in the category of grading-restricted generalized V-modules when V is a vertex operator algebra satisfying the following conditions: 1. V is C_{1}-cofinite in the sense of Li. 2. There existsa positive integer N such that the differences between the real parts of the lowest conformal weights of irreducible V-modules are bounded by N and such that the associative algebra A_{N}(V) is finite dimensional. This result shows that the category of grading-restricted generalized $V$-modules is a finite abelian category over C. Using the existence of projective covers, we prove that if such a vertex operator algebra V satisfies in addition Condition 3, that irreducible V-modules are $\R$-graded and C_{1}-cofinite in the sense of the author, then the category of grading-restricted generalized V-modules is closed under the P(z)-tensor product operation for $z\in C^{\times}. We also prove that other conditions for applying the logarithmic tensor product theory developed by Lepowsky, Zhang and the author hold. Consequently, for such V, this category has a natural structure of braided tensor category. In particular, when V is of positive energy and C_{2}-cofinite, Conditions 1--3 are satisfied and thus all the conclusions hold. |
09/01/2008 | |

On the Projective Hull of Certain Curves in $C^2$ M/07/39 Voir plus > Voir moins >The projective hull X^ of a compact set X in projective n-space P^n is an analogue of the classical polynomial hull of a set in C^n. In the special case that X lies in an affine chart C^n in P^n, the part of X^ lying in C^n can be defined as the set of points x in C^n for which there exists a constant M(x) so that |p(x)| < M(x)^d sup_X|p| for all polynomials p of degree less than or equal to d, and any d > 0. Let X^(M) denote the set of points x where M(x) < M. Using an argument of E. Bishop, we show that if g is a compact real analytic curve in C^2 (not necessarily connected), then for any linear projection p:C^2 --> C^1, that part of g^(M) which lies above z is finite for almost all z in C^1. It is then shown that for anycompact stable real-analytic curve g in P^n, the set g^ - g is a 1-dimensional complex analytic subvariety of P^n - g. |
14/12/2007 | |

Operator-Valued Involutive Distributions of Evolutionary Vector Fields and their Affine Geometry M/07/38 |
04/12/2007 | |

Describing general cosmological singularities in Iwasawa variables P/07/36 |
31/10/2007 | |

When steric hindrance facilitates processivity: polymerase activity within chromatin P/07/37 Voir plus > Voir moins >During eukaryotic transcription, polymerase activity generates torsional stress in DNA, having a negative impact in polymerase processivity. Using our previous studies of the chromatin fiber structure and conformational transitions, we suggest that this torsional stress can be alleviated thanks to a balance between fiber twist and a nucleosome conformational transition into a reversome state. Our model enlightens the origin of polymerase pauses, and leads to the counter-intuitive conclusion that chromatin organized compaction might facilitate polymerase processivity. Indeed, in a compact and well-structured chromatin loop, steric hindrance between nucleosomes enforce sequential transitions, thus ensuring that the polymerase always meets a permissive nucleosomal state. |
31/10/2007 | |

Quelques remarques sur le principe de fonctorialit\'e M/07/31 |
28/10/2007 | |

Dirichlet Duality and the Nonlinear Dirichlet Problem M/07/34 Voir plus > Voir moins >We study the Dirichlet problem for fully nonlinear, degenerate elliptic equations of the form f(Hess u)=0 on a smoothly bounded domain D in R^n. In our approach the equation is replaced by a subset F of the space of symmetric nxn-matrices with bdy(F) contined in the set {f=0}. We establish the existence and uniqueness of continuous solutions under an explicit geometric ``F-convexity'' assumption on the boundary bdy(F). The topological structure of F-convex domains is also studied and a theorem of Andreotti-Frankel type is proved for them. Two key ingredients in the analysis are the use of subaffine functions and Dirichlet duality, both introduced here. Associated to F is a Dirichlet dual set F* which gives a dual Dirichlet problem.This pairing is a true duality in that the dual of F* is F and in the analysis the roles of F and F* are interchangeable. The duality also clarifies many features of the problem including the appropriate conditions on the boundary. Many interesting examples are covered by these results including: All branches of the homogeneous Monge-Ampere equation over R, C and H; equations appearing naturally in calibrated geometry, Lagrangian geometry and p-convex riemannian geometry, and all branches of theSpecial Lagrangian potential equation. |
23/10/2007 | |

Scalar curvature on lightlike hypersurfaces. M/07/35 Voir plus > Voir moins >In a recent paper by K. Duggal, the concept of induced scalar curvature of lightlike hypersurfaces is introduced, restricting on a specific class of the latter. This paper removes some of these constraints and construct this scalar quantity by an approach that is consistent with the well-known nondegenerate theory. Basic calculations supported by examples are provided. |
23/10/2007 | |

Deforming, revolving and resolving - New paths in the string theory landscape P/07/33 Voir plus > Voir moins >In this paper we investigate the properties of series of vacua in the string theory landscape. In particular, we study minima to the flux potential in type IIB compactifications on the mirror quintic. Using geometric transitions, we embed its one dimensional complex structure moduli space in that of another Calabi-Yau with h^{1,1}=86 and h^{2,1}=2. We then show how to construct infinite series of continuously connected minima to the mirror quintic potential by moving into this larger moduli space, applying its monodromies, and moving back. We provide an example of such series, and discuss their implications for the string theory landscape. |
04/10/2007 | |

L'universalisme math\'ematique M/07/29 |
20/09/2007 | |

The diffeomorphism group of a $K3$ surface and Nielsen realization M/07/32 Voir plus > Voir moins >We use moduli spaces of various geometric structures on a manifold M to probe the cohomology of the diffeomorphism group and mapping class group of M. The general principle is that existence of a moduli problem for which the Teichmuller space resembles apoint implies that the homomorphism from the diffeomorphism group (or the mapping class group) to an appropriate discrete group resembles a retraction after applying the classifying space functor. Our main application of this idea is for K^4 a K3 surface;here the maps BDiff(K) --> BAut(H^2(K;Z)) and B\pi_0 Diff(K) --> BAut(H^2(K;Z)) are injective on real cohomology in degrees * < 10. The work of Borel and Matsushima determines the real cohomology of BAut(H^2(K;Z)) in these degrees. Using the above injections, the Borel classes provide cohomological obstructions to a generalized Nielsen realization problem which asks when subgroups of the mapping class group can be lifted to the diffeomorphism group. We conclude that the homomorphism Diff(M) --> \pi_0 Diff(M) does not admit a section if M contains a K3 surface as a connected summand. |
20/09/2007 | |

Constraints and the $E_{10}$ Coset Model P/07/30 Voir plus > Voir moins >We continue the study of the one-dimensional $E_{10}$ coset model (massless spinning particlemotion on $E_{10}/K(E_{10}))$ whose dynamics at low levels is known to coincide with the equations of motion of maximal supergravity theories in appropriate truncations. We show that the coset dynamics (truncated at levels $\ell \leq 3$) can be consistently restricted by requiring the vanishing of a set of constraints which are in one-to-one correspondence with the canonical constraints of supergravity. Hence,the resulting constrained $\sigma$-model dynamics captures the full (constrained) supergravity dynamics in this truncation. Remarkably, the bosonic constraints are found to be expressible in a Sugawara-like (current $\times$ current) form in terms of the conserved $E_{10}$ Noether current, and transform covariantly under an upper parabolic subgroup $E_{10}^+ \subset E_{10}$. We discuss the possible implications of this result, and in particular exhibit a tantalising link with the usual affine Sugawara construction in the truncation of $E_{10}$ to its affine subgroup $E_9$. |
18/09/2007 | |

Restricted set addition: The exceptional case of the Erdos-Heilbronn conjecture M/07/28 Voir plus > Voir moins >Let A,B be different nonempty subsets of the group of integers modulo a prime p. If p is not smaller than |A|+|B|-2, then at least this many residue classes can be represented as a+b, where a and b are different elements of A and B, respectively. This result complements the solution of a problem of Erdos and Heilbronn obtained by Alon, Nathanson, and Ruzsa. |
08/08/2007 | |

Tubular Neighborhoods of Nodal Sets and Diophantine Approximation M/07/27 Voir plus > Voir moins >We give upper and lower bounds on the volume of a tubular neighborhood of the nodal set of an eigenfunction of the Laplacian on a real analytic closed Riemannian manifold M. As an application we consider the question of approximating points on M by nodal sets, and explore analogy with approximation by rational numbers. |
31/07/2007 | |

Hochschild cohomology, the characteristic morphism and derived deformations M/07/26 Voir plus > Voir moins >A notion of Hochschild cohomology of an abelian category was defined by Lowen and Van den Bergh (2005) and they showed the existence of a characteristic morphism from the Hochschild cohomology into the graded centre of the (bounded) derived category. An element in the second Hochschild cohomology corresponds to a first order deformation of the abelian category (Lowen and Van den Bergh, 2006). The problem of deforming single objects of the bounded derived category was treated by Lowen (2005). In this paper we show that the image of the Hochschild cohomology element under the characteristic morphism encodes precisely the obstructions to deforming single objects of the bounded derived category to the bounded derived category of the deformed abelian category. Hence this paper provides a missing link between the above works. Finally we discuss some implications of these facts in the direction of a ``derived deformation theory''. |
24/07/2007 | |

Towards a modulo $p$ Langlands correspondence for GL$_2$ M/07/25 |
04/07/2007 | |

Subgroup separability in residually free groups M/07/24 Voir plus > Voir moins >We prove that the finitely presentable subgroups of residually free groups are separable and that the subgroups of type $FP_\infty$ are virtual retracts. We describe a uniform solution to the membership problem for finitely presentable subgroups of residually free groups. |
29/06/2007 | |

Perverse coherent sheaves and the geometry of special pieces in the unipotent variety M/07/23 Voir plus > Voir moins >Let X be a scheme of finite type over a Noetherian base scheme S admitting a dualizing complex, and let U be an open subscheme whose complement has codimension at least 2. We extend the theory of perverse coherent sheaves, due to Deligne and disseminated by Bezrukavnikov, by showing that a coherent middle extension functor from perverse sheaves on U to perverse sheaves on X may be defined for a much broader class of perversities that has previously been known. We also introduce a derived category version of the coherent middle extension functor. Under suitable hypotheses, we introduce a construction (called "S_2-extension") in terms of perverse coherent sheaves of algebras on Xthat takes a finite morphism to U and extends it in a canonical way to a finite morphism to X. In particular, this construction gives a canonical "S_2-ification" of appropriate X. The construction also has applications to the "Macaulayfication" problem, and it is particularly well-behaved when X is Gorenstein. Our main goal, however, is to address a conjecture of Lusztig on the geometry of special pieces (certain subvarieties of the unipotent variety of a reductive algebraic group). The conjecture asserts in part that each special piece is the quotient of some variety (previously unknown in the exceptional groups and in positive characteristic) by the action of a certain finite group. We use S_2-extension to give a uniform construction of the desired variety. |
28/06/2007 | |

On the derived category of 1-motives, I M/07/22 Voir plus > Voir moins >We consider the category of Deligne 1-motives over a perfect field k of exponential characteristic p and its derived category for a suitable exact structure after inverting p. As a first result, we provide a fully faithful embedding into an 'etale version of Voevodsky's triangulated category of geometric motives. Our second main result is that this full embedding ``almost" has a left adjoint, that we call LAlb. Applied to the motive of a variety we thus get a bounded complex of 1-motives, that we compute fully for smooth varieties and partly for singular varieties. As an application we give motivic proofs of Ro\v\i tman type theorems (in characteristic 0). |
14/06/2007 | |

A remark on quantum gravity P/07/20 Voir plus > Voir moins >We discuss the structure of Dyson--Schwinger equations in quantum gravity and conclude in particular that all relevant skeletons are of first order in the loop number. There is an accompanying sub Hopf algebra on gravity amplitudes equivalent to identities between n-graviton scattering amplitudes which generalize the Slavnov Taylor identities. These identities map the infinite number of charges and finite numbers of skeletons in gravity to an infinite number of skeletons and a finite number of charges needing renormalization. Our analysis suggests that gravity, regarded as a probability conserving but perturbatively non-renormalizable theory, is renormalizable after all, thanks to the structure of its Dyson--Schwinger equations. |
29/05/2007 | |

Wormholes as Black Hole Foils P/07/19 Voir plus > Voir moins >We study to what extent wormholes can mimic the observational features of black holes. It is surprisingly found that many features that could be thought of as 'characteristic' of a black hole (endowed with an event horizon) can be closely mimicked by aglobally static wormhole, having no event horizon. This is the case for: the apparently irreversible accretion of matter down a hole, no-hair properties, quasi-normal-mode ringing, and even the dissipative properties of black hole horizons, such as a finite surface resistivity equal to 377 Ohms. The only way to distinguish the two geometries on an observationally reasonable time scale would be through the detection of Hawking's radiation, which is, however, too weak to be of practical relevance for astrophysical black holes. We point out the existence of an interesting spectrum of quantum microstates trapped in the throat of a wormhole which could be relevant for storing the information 'lost' during a gravitational collapse. |
04/05/2007 | |

Cosmological Singularities and a Conjectured Gravity/Coset Correspondence P/07/15 Voir plus > Voir moins >We review the recently discovered connection between the Belinsky-Khalatnikov-Lifshitz-like "chaotic" structure of generic cosmological singularities in eleven-dimensional supergravity and the "last" hyperbolic Kac-Moody algebra $E_{10}$. This intriguing connection suggests the existence of a hidden "correspondence" between supergravity (or even $M$-theory) and null geodesic motion on the infinite-dimensional coset space $E_{10}/K(E_{10})$. If true, this gravity/coset correspondence would offer a new view of the (quantum) fate of space (and matter) at cosmological singularities. |
13/04/2007 | |

Binary Systems as Test-beds of Gravity Theories P/07/16 Voir plus > Voir moins >We review the general relativistic theory of the motion, and of the timing, of binary systems containing compact objects (neutron stars or black holes). Then we indicate the various ways one can use binary pulsar data to test the strong-field and/or radiative aspects of General Relativity, and of general classes of alternative theories of relativistic gravity. |
13/04/2007 | |

General Relativity Today P/07/17 Voir plus > Voir moins >After recalling the conceptual foundations and the basic structure of general relativity, we review some of its main modern developments (apart from cosmology): (i) the post-Newtonian limit and weak-field tests in the solar system, (ii) strong-gravitational fields and black holes, (iii) strong-field and radiative tests in binary pulsar observations, (iv) gravitational waves, (v) general relativity and quantum theory. |
13/04/2007 | |

Chaos and Symmetry in String Cosmology P/07/18 Voir plus > Voir moins >We review the recently discovered interplay between chaos and symmetry in the general inhomogeneous solution of many string-related Einstein-matter systems in the vicinity of a cosmological singularity. The Belinsky-Khalatnikov-Lifshitz-type chaotic behaviour is found, for many Einstein-matter models (notably those related to the low-energy limit of superstring theory and $M$-theory), to be connected with certain (infinite-dimensional) hyperbolic Kac-Moody algebras. In particular, the billiard chambers describing the asymptotic cosmological behaviour of pure Einstein gravity in spacetime dimension $d+1$, or the metric-three-form system of $11$-dimensional supergravity, are found to be identical to the Weyl chambers of the Lorentzian Kac-Moody algebras $AE_d$, or $E_{10}$, respectively. This suggests that these Kac-Moody algebras are hidden symmetries of the corresponding models. There even exists some evidence of a hidden equivalence between the general solution of the Einstein-three-form system and a null geodesic in the infinite dimensional coset space $E_{10} / K (E_{10})$, where $K (E_{10})$ is the maximal compact subgroup of $E_{10}$. |
13/04/2007 | |

Local Asymmetry and the Inner Radius of Nodal Domains M/07/14 Voir plus > Voir moins >Let M be a closed Riemannian manifold of dimension n. Let f be an eigenfunction of the Laplace-Beltrami operator corresponding to an eigenvalue lambda. We show that the volume of {f>0} inside any ball B whose center lies on {f=0} is > C|B|/lambda^n. Weapply this result to prove that each nodal domain contains a ball of radius > C/lambda^n. |
12/04/2007 | |

B$_{\rm cris}^{\varphi = 1}$-représentations et $(\varphi , \Gamma)$-modules M/07/13 |
12/04/2007 | |

The cyclomatic number of connected graphs without solvable orbits M/07/12 Voir plus > Voir moins >A graph is without solvable orbits if its group of automorphisms acts on each of its orbits through a non-solvable quotient. We prove that there is a connected graph without solvable orbits of cyclomatic number c if and only if c is equal to 6, 8, 10, 11, 15, 16, 19, 20, 21, 22, or is at least 24, and briefly discuss the geometric consequences. |
05/04/2007 | |

The Geometry of Small Causal Diamonds P/07/11 Voir plus > Voir moins >The geometry of causal diamonds or Alexandrov open sets whose initial and final events $p$ and $q$ respectively have a proper-time separation $ au$ small compared with the curvature scale is a universal. The corrections from flat space are given as a power series in $ au$ whose coefficients involve the curvature at the centre of the diamond. We give formulae for the total 4-volume $V$ of the diamond, the area $A$ of the intersection the future light cone of $p$ with the past light coneof$q$ and the 3-volume of the hyper-surface of largest 3-volume bounded by this intersection valid to ${cal O } ( au ^4) $. The formula for the 4-volume agrees with a previous result of Myrheim. Remarkably, the iso-perimetric ratio ${3V_3 øver 4 pi }/({ A øver 4 pi } ) ^{3 øver 2} $ depends only on the energy density at the centre and is bigger than unity if the energy density is positive. These results are also shown to hold in all spacetime dimensions. Formulae are also given, valid to nextnon-trvial order, for causal domains in two spacetime dimensions. We suggest a number of applications, for instance, the directional dependence of the volume allows one to regard the volumes of causal diamonds as an observable providing a measurement of the Ricci tensor. |
14/03/2007 | |

An $A_{\infty}$-structure for lines in a plane M/07/10 Voir plus > Voir moins >As an explicit example of an $A_{\infty}$-structure associated to geometry, we construct an $A_{\infty}$-structure for a Fukaya category of finitely many lines (Lagrangians) in $R^2$, ie., we define also non-transversal $A_{\infty}$-products. This construction is motivated by homological mirror symmetry of (two-)tori, where $R^2$ is the covering space of a two-torus. The strategy is based on an algebraic reformulation of Morse homotopy theory through homological perturbation theory (HPT) as discussed by Kontsevich and Soibelman in cite{KoSo}, where we introduce a special DG category which is a key idea of our construction. |
06/03/2007 | |

A vanishing theorem in positive characteristic and tilting equivalences M/07/09 |
02/03/2007 | |

Notes on instantons in topological field theory and beyond P/07/08 |
21/02/2007 | |

Renormalisation of non-commutative field theories P/07/07 Voir plus > Voir moins >The first renormalisable quantum field theories on non-commutative space have been found recently. We review this rapidly growing subject. |
13/02/2007 | |

Familles de représentations de De Rham et monodromie p-adique M/07/06 |
08/02/2007 | |

One-loop Beta Functions for the Orientable Non-commutative Gross-Neveu Model P/07/05 Voir plus > Voir moins >We compute at the one-loop order the beta-functions for a renormalisable non-commutative analog of the Gross-Neveu model defined on the Moyal plane. The calculation is performed within the so called x-space formalism. We find that this non-commutative field theory exhibits asymptotic freedom for any number of colors. The beta-function for the non-commutative counterpart of the Thirring model is found to be non vanishing. |
02/02/2007 | |

A counterexample to Premet's and Joseph's conjectures M/07/01 Voir plus > Voir moins >Let $g$ be a finite-dimensional reductive Lie algebra of rank $l$ over an algebraically closed field of characteristic zero. Given an element $x$ of $g$, we denote by $g_x$ the centraliser of $x$ in $g$. It was conjectured by Premet, that the algebra $S(g_x)^{g_x}$ of the symmetrci $mathfrak g_x$-invariants is a graded polynomial algebra in $l$ variables. In this note, we show that this conjecture does not hold for the minimal nilpotent orbit in the simple Lie algebra of type $E_8$. As a consequence, a conjecture of Joseph on the semi-invariants of (bi)parabolics is not true either. |
26/01/2007 | |

Lifetime of a massive particle in a de Sitter universe P/07/02 Voir plus > Voir moins >We study particle decay in de Sitter space-time as given by first order perturbation theory in an interacting quantum field theory. We show that for fields with masses above a critical mass $m_c$ there is no such thing as particle stability, so thatdecays forbidden in flat space-time do occur there. The lifetime of such a particle also turns out to be independent of its velocity when that lifetime is comparable with de Sitter radius. Particles with lower mass are even stranger: The masses of their decay products must obey quantification rules, and their lifetime is zero. |
26/01/2007 | |

Semi-classical open string corrections and symmetric Wilson loops P/07/03 Voir plus > Voir moins >In the AdS/CFT correspondence, an AdS_2 x S^2 D3-brane with electric flux in AdS_5 x S^5 spacetime corresponds to a circular Wilson loop in the symmetric representation or a multiply wound one in N=4 super Yang-Mills theory. In order to distinguish the symmetric loop and the multiply wound loop, one should see an exponentially small correction in large 't Hooft coupling. We study semi-classically the disk open string attached to the D3-brane. We obtain the exponent of the term and it agrees with the result of the matrix model calculation of the symmetric Wilson loop. |
26/01/2007 | |

Geometry of differential equations M/07/04 Voir plus > Voir moins >This is a review of classical and modern methods of geometric-algebraic approach to (overdeteremined) systems of partial differential equations. |
26/01/2007 | |

Recursion and growth estimates in renormalizable quantum field theory P/06/62 Voir plus > Voir moins >In this paper we show that there is a Lipatov bound for the radius of convergence for superficially divergent one-particle irreducible Green functions in a renormalizable quantum field theory if there is such a bound for the superficially convergent ones. The radius of convergence turns out to be ${ m min}{ ho,1/b_1}$, where $ ho$ is the bound on the convergent ones, the instanton radius, and $b_1$ the first coefficient of the $eta$-function. |
19/12/2006 | |

Comparaison des théories de Deitmar et de Zhu M/06/63 |
19/12/2006 | |

The next-to-ladder approximation for Dyson-Schwinger equations P/06/64 Voir plus > Voir moins >We solve the linear Dyson Schwinger equation for a massless vertex in Yukawa theory, iterating the first two primitive graphs. |
19/12/2006 | |

Extended Seiberg-Witten Theory and Integrable Hierarchy P/06/43 |
08/12/2006 | |

Sur un `corps de caractéristique 1' (d'après Zhu) M/06/61 Voir plus > Voir moins >Nous exposons la théorie de Zhu concernant un analogue formel du corps ${mathbf F}_{p}$, pour `$p=1$'. |
06/12/2006 | |

Homotopy graph-complex for configuration and knot spaces M/06/58 Voir plus > Voir moins >In the paper we prove that the primitive part of the Sinha homology spectral sequence E2-term for the space of long knots is rationally isomorphic to the homotopy E2-term. We also define natural graph-complexes computing the rational homotopy of configuration and of knot spaces. |
05/12/2006 | |

Modified Hochschild and Periodic Cyclic Homology M/06/59 Voir plus > Voir moins >The Hochschild and (periodic) cyclic homology of the algebra of continuous functions on a smooth manifold are trivial. In this paper we create an analogue of the Hochschild and periodic cyclic homology which gives the right result when applied onto the algebra of continuous functions on smooth manifolds ($Z_{2}$-graded de Rham co-homology of the manifold). This is realized by replacing the Connes periodic bi-complex (b, B) by the bi-complex $( ilde{b}, d),$ where the operator $ ilde{b}$ is obtained by blending the Hochschild boundary $b$ with the Alexander-Spanier boundary $d$; the operator $ ilde{b}$ anti-commutes with the operator $d$. In order to reach this objective, as in the classical case, one has to consider the Alexander-Spanier complex of germs. As the notion of germ is a locality notion, our procedure will apply to topological algebras. The problem of producing a tool able to extract the correct homology from the algebra of continuous functions was addressed before byM. Puschnigg. |
05/12/2006 | |

A generalization of residual finiteness M/06/60 Voir plus > Voir moins >The concept of residual finiteness with respect to automorphic equivalence, a property generalizing residual finiteness and conjugacy separability is introduced. A sufficient condition for a group G to be residually finite with respect to automorphic equivalence is proven (Theorem). It is then used to give some examples of automorphic equivalent residually finite groups. |
05/12/2006 | |

Noncommutative Geometry Approach to Principal and Associated Bundles M/06/65 |
01/12/2006 | |

The map from the cyclohedron to the associahedron is left cofinal M/06/66 Voir plus > Voir moins >Two natural projections from the cyclohedron to the associahedron are defined. We show that the preimages of any point via these projections might not be homeomorphic to (a cell decomposition of) a disc, but are still contractible. We briefly explain anapplication of this result to the study of knot spaces from the point of view of the Goodwillie-Weiss embedding calculus. |
01/12/2006 | |

Injectivity Radius of Lorentzian Manifolds M/06/67 |
01/12/2006 | |

Reduction Theorems for characteristic functors on finite $p$-groups and applications to $p$-nilpotence criteria M/06/55 |
22/11/2006 | |

Strongly homotopy Lie bialgebras and Lie quasi-bialgebras M/06/57 Voir plus > Voir moins >Structures of Lie algebras, Lie coalgebras, Lie bialgebras and Lie quasibialgebras are presented as solutions of Maurer-Cartan equations on corresponding governing differential graded Lie algebras. Cohomology theories of all these structures are described in a concise way using the big bracket construction of Kosmann-Schwarzbach. This approach provides a definition of an $L_infty$-(quasi)bialgebra (strong homotopy Lie (quasi)bialgebra). We recover an $L_infty$-algebra structure as a particularcase of our construction. The formal geometry interpretation leads to a definition of an $L_infty$ (quasi)bialgebra structure on $V$ as a differential operator $Q$ on $V,$ self-commuting with respect to the Poisson bracket. Finally, we establish an $L_infty$-version of a Manin (quasi) triple and get a correspondence theorem with $L_infty$-(quasi) bialgebras. |
21/11/2006 | |

Cardy condition for Open-closed field algebras M/06/56 Voir plus > Voir moins >Let $V$ be a vertex operator algebra satisfying certain reductivity and finiteness conditions such that $mathcal{C}_V$, the category of $V$-modules, is a modular tensor category. We study open-closed field algebras over $V$ equipped with nondegenerateinvariant bilinear forms for both open and closed sectors. We show that they give algebras over certain $C$-extension of the Swiss-cheese partial dioperad, and we obtain Ishibashi states easily in such algebras. We formulate Cardy condition algebraically in terms of the action of the modular transformation $S: au mapsto -frac{1}{ au}$ on the space of intertwining operators. We then derive a graphical representation of $S$ in the modular tensor category $mathcal{C}_V$. This result enablesus to give a categorical formulation of Cardy condition and modular invariant conformal full field algebra over $Vøtimes V$. Then we incorporate the modular invariance condition for genus-one closed theory, Cardy condition and the axioms for open-closed field algebra over $V$ equipped with nondegenerate invariant bilinear forms into a tensor-categorical notion called Cardy $mathcal{C}_V|mathcal{C}_{Vøtimes V}$-algebra. We also give a categorical construction of Cardy $mathcal{C}_V|mathcal{C}_{Vøtimes V}$-algebra in Cardy case. |
15/11/2006 | |

Field rotation parameters and limit cycle bifurcations M/06/54 Voir plus > Voir moins >In this paper, the global qualitative analysis of planar polynomial dynamical systems is established and a new geometric approach to solving Hilbert's Sixteenth Problem on the maximum number and relative position of their limit cycles in two special cases of such systems is suggested. First, using geometric properties of four field rotation parameters of a new canonical system which is constructed in this paper, we present a proof of our earlier conjecture that the maximum number of limit cycles ina quadratic system is equal to four and the only possible their distribution is (3:1). Then, by means of the same geometric approach, we solve the Problem for Li'{e}nard's polynomial system (in this special case, it is considered as Smale's Thirteenth Problem). Besides, generalizing the obtained results, we present a solution of Hilbert's Sixteenth Problem on the maximum number of limit cycles surrounding a singular point for an arbitrary polynomial system and, applying the Wintner-Perko terminationprinciple for multiple limit cycles, we develop an alternative approach to solving the Problem. By means of this approach, for example, we give another proof of the main theorem for a quadratic system and complete the global qualitative analysis ofa generalized Li'{e}nard's cubic system with three finite singularities. We discuss also some different approaches to the Problem. |
08/11/2006 | |

Correlator of Fundamental and Anti-symmetric Wilson loops in AdS/CFT Correspondence P/06/53 |
27/10/2006 | |

Instantons beyond topological theory I P/06/42 Voir plus > Voir moins >Many quantum field theories in one, two and four dimensions possess remarkable limits in which the instantons are present, the anti-instantons are absent, and the perturbative corrections are reduced to one-loop. We analyze the corresponding models as full quantum field theories, beyond their topological sector. We show that the correlation functions of all, not only topological (or BPS), observables may be studied explicitly in these models, and the spectrum may be computed exactly. An interesting feature is that the Hamiltonian is not always diagonalizable, but may have Jordan blocks, which leads to the appearance of logarithms in the correlation functions. We also find that in the models defined on Kahler manifolds the space of states exhibits holomorphic factorization. We conclude that in dimensions two and four our theories are logarithmic conformal field theories. |
17/10/2006 | |

Open-closed field algebras, operads and tensor categories M/06/51 Voir plus > Voir moins >We introduce the notions of open-closed field algebra and open-closed field algebra over a vertex operator algebra $V$. In the case that $V$ satisfies certain finiteness and reductivity conditions, we show that an open-closed field algebra over $V$ canonically gives an algebra over a $C$-extension of the Swiss-cheese partial operad. We also give a tensor categorical formulation and categorical constructions of open-closed field algebras over $V$. |
10/10/2006 | |

Classification of low energy sign-changing solutions of an almost critical problem M/06/52 Voir plus > Voir moins >In this paper we make the analysis of the blow-up of low energy sign-changing solutions of a semi-linear elliptic problem involving nearly critical exponent. Our results allow to classify these solutions according to the concentration speeds of the positive and negative part and, in high dimensions, lead to complete classification of them. Additional qualitative results, such as symmetry or location of the concentration points are obtained when the domain is a ball. |
10/10/2006 | |

Remarks on compact shrinking Ricci solitons of dimension four M/06/50 |
03/10/2006 | |

A primer of Hopf algebras M/06/40 Voir plus > Voir moins >In this paper, we review a number of basic results about so-called Hopf algebras. We begin by giving a historical account of the results obtained in the 1930's and 1940's about the topology of Lie groups and compact symmetric spaces. The climax is provided by the structure theorems due to Hopf, Samelson, Leray and Borel. The main part of this paper is a thorough analysis of the relations between Hopf algebras and Lie groups (or algebraic groups). We emphasize especially the category of unipotent (and prounipotent) algebraic groups, in connection with Milnor-Moore's theorem. These methods are a powerful tool to show that some algebras are free polynomial rings. The last part is an introduction to the combinatorial aspects of polylogarithm functions andthecorresponding multiple zeta values. |
26/09/2006 | |

Rigidity theorem for expanding Gradient Ricci Solitons M/06/49 Voir plus > Voir moins >In this paper, we study the rigidity problem for expanding gradient Ricci soliton equation on a complete conformally compact Riemannian manifold. We show that under a natural condition on the Ricci curvature and the scalar curvature, the expanding Ricci soliton is Poincare-Einstein. |
21/09/2006 | |

Linear dependence in Mordell-Weil groups M/06/48 Voir plus > Voir moins >We consider a local to global principle for detecting linear dependence of nontorsion points, by reduction maps, in the Mordell-Weil group of an abelian variety defined over a number field. |
19/09/2006 | |

A Lie theoretic approach to renormalization P/06/46 Voir plus > Voir moins >Motivated by recent work of Connes and Marcolli, based on the Connes-Kreimer approach to renormalization, we augment the latter by a combinatorial, Lie algebraic point of view. Our results rely both on the properties of the Dynkin idempotent, one of the fundamental Lie idempotents in the theory of free Lie algebras, and on the fine properties of Hopf algebras and their associated descent algebras. Besides leading very directly to proofs of the main combinatorial properties of the renormalization procedures, the new techniques do not depend on the geometry underlying the particular case of dimensional regularization and the Riemann-Hilbert correspondence. This is illustrated with a discussion of the BPHZ renormalization scheme. |
13/09/2006 | |

Le Calcul des Probabilités de Poincaré M/06/47 Voir plus > Voir moins >Résumé: Le présent texte est extrait d'un ouvrage à paraître sur `L'héritage mathématique de Poincaré' (éditions Belin). Il s'agit d'une analyse du livre de Poincaré sur les probabilités, qui reprend l'un de ses cours, et son texte fameux sur le hasard. Le plus intéressant est la manière dont Poincaré traite des problèmes de théorie cinétique des gaz et des cheminements aléatoires. Abstract: We analyse the classical work of Poincaré about probability theory. This report is part of a forthcoming book on the `Mathematical Heritage of Poincaré'. We focus on the relevance of the book for the development of statistical physics and random walks. |
13/09/2006 | |

Multiloop Superstring Amplitudes from Non-Minimal Pure Spinor Formalism P/06/41 Voir plus > Voir moins >Using the non-minimal version of the pure spinor formalism, manifestly super-Poincare covariant superstring scattering amplitudes can be computed as in topological string theory without the need of picture-changing operators. The only subtlety comes fromregularizing the functional integral over the pure spinor ghosts. In this paper, it is shown how to regularize this functional integral in a BRST-invariant manner, allowing the computation of arbitrary multiloop amplitudes. The regularization method simplifies for scattering amplitudes which contribute to ten-dimensional F-terms, i.e. terms in the ten-dimensional superspace action which do not involve integration over the maximum number of $ heta$'s. |
06/09/2006 | |

Dessins d'enfants: Solving equations determining Belyi pairs M/06/44 Voir plus > Voir moins >This paper deals with the Grothendieck dessins d'enfants, that is tamely embedded graphs on surfaces. We investigate combinatorics of systems of equations determining corresponding Belyi pair, that is a rational function with at most 3 critical values onan algebraic curve, such that its preimage is the dessin under consideration. Several properties of extra, or so-called parasitic, solutions of such systems are described. |
05/09/2006 | |

Dyson Schwinger Equations: From Hopf algebras to Number Theory P/06/45 Voir plus > Voir moins >We consider the structure of renormalizable quantum field theories from the viewpoint of their underlying Hopf algebra structure. We review how to use this Hopf algebra and the ensuing Hochschild cohomology to derive non-perturbative results for the short-distance singular sector of a renormalizable quantum field theory. We focus on the short-distance behaviour and thus discuss renormalized Green functions $G_R(alpha,L)$ which depend on a single scale $L=ln q^2/mu^2$. |
05/09/2006 | |

Séries hypergéométriques multiples et polyzêtas M/06/36 Voir plus > Voir moins >Nous décrivons un algorithme théorique et effectif permettant de démontrer que des séries et intégrales hypergéométriques multiples relativement générales se décomposent en combinaisons linéaires à coefficients rationnels de polyzêtas. |
29/06/2006 | |

Phénomènes de symétries dans des formes linéaires en polyzêtas M/06/37 Voir plus > Voir moins >On donne deux généralisations, en profondeur quelconque, du phénomène de symétrie utilisé par Ball-Rivoal pour démontrer qu'une infinité de valeurs de la fonction zeta de Riemann aux entiers impairs sont irrationnelles. Ces généralisations concernent des séries multiples de type hypergéométrique qui s'écrivent comme formes linéaires en certains polyzêtas. La preuve utilise notamment la régularisation des polyzêtas à divergence logarithmique. |
29/06/2006 | |

Tensor gauge fields in arbitrary representations of $GL(D,{\bf R})$: II. Quadratic actions P/06/33 Voir plus > Voir moins >Quadratic, second-order, non-local actions for tensor gauge fields transforming in arbitrary irreducible representations of the general linear group Quadratic, second-order, non-local actions for tensor gauge fields transforming in arbitrary irreduciblein $D$-dimensional Minkowski space are explicitly written in a compact form by making use of Levi--Civita tensors. The field equations derivedfrom these actions ensure the propagation of the correct massless physical degrees of freedom and are shown to be equivalent to non-Lagrangian local field equations proposed previously.Moreover, these actions allow a frame-like reformulation \`a la MacDowell--Mansouri, without any trace constraint in the tangent indices. |
29/06/2006 | |

On matrix differential equations in the Hopf algebra of renormalization P/06/38 |
29/06/2006 | |

Bounds for the dimensions of $p$-adic multiple $L$-value spaces M/06/39 Voir plus > Voir moins >First, we will define $p$-adic multiple $L$-values ($p$-adic MLV's), which are generalizations of Furusho's $p$-adic multiple zeta values ($p$-adic MZV's) in Section 2. Next, we prove bounds for the dimensions of $p$-adic MLV-spaces in Section 3, assuming results in Section 4. The bounds come from the rank of $K$-groups of ring of $S$-integers of cyclotomic fields, and these are $p$-adic analogues of Deligne-Goncharov's bounds for the dimensions of (complex) MLV-spaces. In the case of MLV-spaces, the gap between the dimensions and the bounds is related to spaces of modular forms similarly as the complex case. In Section 4, we define the crystalline realization of mixed Tate motives and show a comparison isomorphism, by uing $p$-adic Hodge theory. |
29/06/2006 | |

Quantum effects in gravitational wave signals from cuspy superstrings P/06/35 Voir plus > Voir moins >We study the gravitational emission, in Superstring Theory, from fundamental strings exhibiting cusps. The classical computation of the gravitational radiation signal from cuspy strings features strong bursts in the special null directions associated to the cusps. We perform a quantum computation of the gravitational radiation signal from a cuspy string, as measured in a gravitational wave detector using matched filtering and located in the special null direction associated to the cusp. We study the quantum statistics (expectation value and variance) of the measured filtered signal and find that it is very sharply peaked around the classical prediction. Ultimately, this result follows from the fact that the detector is a low-pass filter which is blind tothe violent high-frequency quantum fluctuations of both the string worldsheet, and the incoming gravitational field. |
23/06/2006 | |

Notes on A-infinity algebras, A-infinity categories and non-commutative geometry. I M/06/34 Voir plus > Voir moins >We develop geometric approach to A-infinity algebras and A-infinity categories based on the notion of formal scheme in the category of graded vector spaces. Geometric approach clarifies several questions, e.g. the notion of homological unit or A-infinity structure on A-infinity functors. We discuss Hochschild complexes of A-infinity algebras from geometric point of view. The paper contains homological versions of the notions of properness and smoothness of projective varieties as well as the non-commutative version of Hodge-to-de Rham degeneration conjecture. We also discuss a generalization of Deligne's conjecture which includes both Hochschild chains and cochains. We conclude the paper with the description of an action of the PROP of singular chains of the topological PROP of 2-dimensional surfaces on the Hochschild chain complex of an A-infinity algebra with the scalar product (this action is more or less equivalent to the structure of 2-dimensional Topological Field Theory associated with an ``abstract'' Calabi-Yau manifold). |
21/06/2006 | |

$K(E_{10})$, Supergravity and Fermions P/06/28 Voir plus > Voir moins >We study the fermionic extension of the E10/K(E10) coset model and its relation to eleven-dimensional supergravity. Finite-dimensional spinor representations of the compact subgroup K(E10) of E(10,R) are studied and the supergravity equations are rewritten using the resulting algebraic variables. The canonical bosonic and fermionic constraints are also analysed in this way, and the compatibility of supersymmetry with local K(E10) is investigated. We find that all structures involving A9 levels 0,1 and 2 nicely agree with expectations, and provide many non-trivial consistency checks of the existence of a supersymmetric extension of the E10/K(E10) coset model, as well as a new derivation of the `bosonic dictionary' between supergravity and coset variables.However, there are also definite discrepancies in some terms involving level 3, which suggest the need for an extension of the model to infinite-dimensional faithful representations of the fermionic degrees of freedom. |
15/06/2006 | |

Coherent algebras and noncommutative projective lines M/06/32 Voir plus > Voir moins >A well-known conjecture says that every one-relator discrete group is coherent. We state and partly prove an analogous statement for graded associative algebras. In particular, we show every that Gorenstein algebra $A$ of global dimension 2 is graded coherent. This allows us to define a noncommutative analogue of the projective line $PP1$ as a noncommutative scheme based on the coherent noncommutative spectrum $cohp A$ of such an algebra $A$, that is, the category of coherent $A$-modulesmodulo the torsion ones. This category is always abelian Ext-finite hereditary with Serre duality, like the category of coherent sheaves on $PP1$. In this way, we obtain a sequence $PP1_n $ ($nge 2$) of pairwise non-isomorphic noncommutative schemes which generalize the scheme $PP1 = PP1_2$. |
13/06/2006 | |

About the Trimmed and the Poincaré-Dulac normal form of diffeomorphisms M/06/29 Voir plus > Voir moins >We study two particular continuous prenormal forms as defined by Jean Ecalle and Bruno Vallet for local analytic diffeomorphism: the Trimmed form and the Poincare-Dulac normal form. We first give a self-contain introduction to the mould formalism of Jean Ecalle. We provide a dictionary between moulds and the classical Lie algebraic formalism using non-commutative formal power series. We then give full proofs and details for results announced by J. Ecalle and B. Vallet about the Trimmed form of diffeomorphisms. We then discuss a mould approach to the classical Poincare-Dulac normal form of diffeomorphisms. We discuss the universal character of moulds taking place in normalization problems. |
07/06/2006 | |

Fractional embedding of differential operators and Lagrangian systems M/06/30 Voir plus > Voir moins >This paper is a contribution to the general program of embedding theories of dynamical systems. Following our previous work on the Stochastic embedding theory developed with S. Darses, we define the fractional embedding of differential operators and ordinary differential equations. We construct an operator combining in a symmetric way the left and right (Riemann-Liouville) fractional derivatives. For Lagrangian systems, our method provide a fractional Euler-Lagrange equation. We prove, developing the corresponding fractional calculus of variations, that such equation can be derived via a fractional least-action principle. We then obtain naturally a fractional Noether theorem and a fractional Hamiltonian formulation of fractional Lagrangian systems. All these constructions are coherents, i.e. that the embedding procedure is compatible with the fractional calculus of variations. We then extend our results to cover the Ostrogradski formalism. Using the fractional embedding and following a previous work of F. Riewe, we obtain a fractional Ostrogradski formalism which allows us to derive non-conservative dynamical systems via a fractional generalized least-action principle. We also discuss the Whittaker equation and obtain a fractional Lagrangian formulation. Last, we discuss the fractional embedding of continuous Lagrangian systems. In particular, we obtain a fractional Lagrangian formulation of the classical fractional wave equation introduced by Schneider and Wyss as well as the fractional diffusion equation. |
07/06/2006 | |

Mode conversion in the cochlea? linear analysis P/06/31 Voir plus > Voir moins >It is suggested that the frequency selectivity of the ear may be based on the phenomenon of mode conversion rather than critical layer resonance. The distinction is explained and supporting evidence discussed. |
07/06/2006 | |

Stochastic Embedding of Dynamical Systems M/06/27 |
19/05/2006 | |

Théorème de Noether stochastique M/06/25 |
17/05/2006 | |

Non-differentiable deformations of $R^n$ M/06/26 Voir plus > Voir moins >Many problems of physics or biology involve very irregular objects like the rugged surface of a malignant cell nucleus or the structure of space-time at the atomic scale. We define and study non-differentiable deformations of the classical Cartesian space $R^n$ which can be viewed as the basic bricks to construct irregular objets. They are obtain by taking the topological product of $n$-graphs of nowhere differentiable real valued functions. Our point of view is to replace the study of a non-differentiable function by the dynamical study of a one-parameter family of smooth regularization of this function. In particular, this allows us to construct a one parameter family of smooth coordinates systems on non-differentiable deformations of $R^n$ whichdepend on the smoothing parameter via an explicit differential equation called a scale-law. Deformations of $R^n$ are examples of a new class of geometrical objects called scale manifolds which are defined in this paper. As an application, we derive rigorously the main results of the scale relativity theory developed by L. Nottale in the framework of a Scale space-time manifold. |
17/05/2006 | |

Etude for linear Dyson-Schwinger Equations P/06/23 Voir plus > Voir moins >We discuss properties of linear Dyson-Schwinger equations. |
10/05/2006 | |

An Etude in non-linear Dyson-Schwinger equations P/06/24 Voir plus > Voir moins >We show how to use the Hopf algebra structure of quantum field theory to derive nonperturbative results for the short-distance singular sector of a renormalizable quantum field theory in a simple but generic example. We discuss renormalized Green functions $G_R(alpha,L)$ in such circumstances which depend on a single scale $L=ln q^2/mu^2$ and start from an expansion in the scale $G_R(alpha,L)=1+sum_k gamma_k(alpha)L^k$. We derive recursion relations between the $gamma_k$ which make full use of the renormalization group. We then show how to determine the Green function by the use of a Mellin transform on suitable integral kernels. We exhibit our approach in an example for which we find a functional equation relating weak and strong coupling expansions. |
10/05/2006 | |

Constructing conformal field theory models P/06/05 |
09/05/2006 | |

Calcul Moulien M/06/22 |
09/05/2006 | |

Curvature corrections and Kac-Moody compatibility conditions P/06/21 Voir plus > Voir moins >We study possible restrictions on the structure of curvature corrections to gravitational theories in the context of their corresponding Kac--Moody algebras, following the initial work on E10 in Class. Quant. Grav. 22 (2005) 2849. We first emphasize thatthe leading quantum corrections of M-theory can be naturally interpreted in terms of (non-gravity) fundamental weights of E10. We then heuristically explore the extent to which this remark can be generalized to all over-extended algebras by determining which curvature corrections are compatible with their weight structure, and by comparing these curvature terms with known results on the quantum corrections for the corresponding gravitational theories. |
26/04/2006 | |

Evolution in random environment and structural instability M/06/20 Voir plus > Voir moins >We consider stability and evolution of complex biological systems in particular, genetic networks. We focus our attention on supporting of homeostasis in these systems with respect to fluctuations of an external medium (the problem is posed by M. Gromov, A.Carbone cite{Gr}). Using a measure of stochastic stability we show that a generic system with fixed parameters is unstable, i.e., the probability to support homeostasis converges to zero as time $T o infty$. However, if we consider a population of unstable systems, which are capable to evolve (change their parameters), then such a population can be stable as $T o infty$. This means that the probability to survive may be non-zero as $T o infty$. Evolution algorithms, that provide stability of populations, are not trivial. We show that the mathematical results on evolution algorithms are consistent with experimental data on genetic evolution. |
13/04/2006 | |

L'isomorphisme entre les tours de Lubin-Tate et de Drinfeld au niveau des points M/06/19 |
11/04/2006 | |

Wilson Loops of Anti-symmetric Representation and D5-branes P/06/18 Voir plus > Voir moins >We use a D5-brane with electric flux in AdS_5 x S^5 background to calculate the circular Wilson loop of anti-symmetric representation in N=4 super Yang-Mills theory in 4 dimensions. The result agrees with the Gaussian matrix model calculation. |
30/03/2006 | |

Nonequilibrium statistical mechanics and entropy production in a classical infinite system of rotators. P/06/17 |
29/03/2006 | |

Matrix Representation of Renormalization in Perturbative Quantum Field Theory P/06/15 Voir plus > Voir moins >We formulate the Hopf algebraic approach of Connes and Kreimer to renormalization in perturbative quantum field theory using triangular matrix representation. We give a Rota-Baxter anti-homomorphism from general regularized functionals on the Feynmangraph Hopf algebra to triangular matrices with entries in a Rota--Baxter algebra. For characters mapping to the group of unipotent triangular matrices we derive the algebraic Birkhoff decomposition for matrices using Spitzer's identity. This simple matrix factorization is applied to characterize and calculate perturbative renormalization. |
28/03/2006 | |

L'isomorphisme entre les tours de Lubin-Tate et de Drinfeld : Décomposition cellulaire de la tour de Lubin-Tate M/06/16 Voir plus > Voir moins >Cet article est le premier d'une série visant à construire un isomorphisme entre les tours p-adiques de Lubin-Tate et de Drinfeld, décrire cet isomorphisme et en donner des applications. Nous-y construisons un modèle entier p-adique équivariant en niveauinfini de la tour de Lubin-Tate. Ce schéma formel p-adique sera comparé plus tard à un autre associé à la tour de Drinfeld. |
28/03/2006 | |

Birkhoff type decompositions and the Baker--Campbell--Hausdorff recursion P/06/14 Voir plus > Voir moins >We describe a unification of several apparently unrelated factorizations arisen from quantum field theory, vertex operator algebras, combinatorics and numerical methods in differential equations. The unification is given by a Birkhoff type decompositionthat was obtained from the Baker-Campbell-Hausdorff formula in our study of the Hopf algebra approach of Connes and Kreimer to renormalization in perturbative quantum field theory. There we showed that the Birkhoff decomposition of Connes and Kreimer canbe obtained from a certain Baker-Campbell-Hausdorff recursion formula in the presence of a Rota-Baxter operator. We will explain how the same decomposition generalizes the factorization of formal exponentials and uniformization for Lie algebras that arose in vertex operator algebra and conformal field theory, and the even-odd decomposition of combinatorial Hopf algebra characters as well as to the Lie algebra polar decomposition as used in the context of the approximation of matrix exponentials in ordinary differential equations. |
23/03/2006 | |

The structure of double groupoids M/06/13 Voir plus > Voir moins >We give a general description of the structure of a discrete double groupoid (with an extra, quite natural, filling condition) in terms of groupoid factorizations and groupoid 2-cocycles with coefficients in abelian group bundles. Our description goesas follows: in a first step we prove that every double groupoid is obtained as an extension of its pith groupoid, which is an abelian group bundle, by its frame double groupoid. The frame satisfies that every box is determined by its edges, and thusis called a 'thin' double groupoid. In a second, independent, step we prove that every thin double groupoid with filling condition is completely determined by a factorization of a certain canonically defined 'diagonal' groupoid. |
22/03/2006 | |

First steps towards p-adic Langlands functoriality M/06/12 Voir plus > Voir moins >By the theory of Colmez and Fontaine, a de Rham representation of the Galois group of a local field roughly corresponds to a representation of the Weil-Deligne group equipped with an admissible filtration on the underlying vector space. Using a modification of the classical local Langlands correspondence, we associate with any pair consisting of a Weil-Deligne group representation and a type of a filtration (admissible or not) a specific locally algebraic representation of a general linear group. We advertise the conjecture that this pair comes from a de Rham representation if and only if the corresponding locally algebraic representation carries an invariant norm. In the crystalline case, the Weil-Deligne group representation is unramified and the associated locally algebraic representation can be studied using the classical Satake isomorphism. By extending the latter to a specific norm completion of the Hecke algebra, we show that the existence of an invariant norm implies that our pair, indeed, comes from a crystalline representation. We also show, by using the formalism of Tannakian categories, that this latter fact is compatible with classical unramified Langlands functoriality and therefore generalizes to arbitrary split reductive groups. |
21/03/2006 | |

Existence of closed $G_2$-structures on 7-manifolds M/06/11 Voir plus > Voir moins >In this note we propose a new way of constructing compact 7-manifolds with a closed $G_2$-structure. As a result we find a first example of a closed $G_2$-structure on $S^3 imes S^4$. We also prove that any integral closed $G_2$-structure on a compact7-manifold $M^7$ can be obtained by embedding $M^7$ to a universal space $(W ^{3(80 +8 cdot C^3 _8)}, h)$. |
08/03/2006 | |

Existence d'immeubles triangulaires quasi-périodiques M/06/08 |
03/03/2006 | |

Ergodic pumping: a mechanism to drive biomolecular conformation changes P/06/09 Voir plus > Voir moins >We propose that a significant contribution to the power stroke of myosin and similar conformation changes in other biomolecules is the pressure of a single molecule (e.g. a phosphate ion) expanding a trap, a mechanism we call ``ergodic pumping''. We demonstrate the principle with a toy computer model and discuss the mathematics governing the evolution of slow degrees of freedom in large Hamiltonian systems. We indicate in detail how the mechanism could fit with known features of the myosin cycle. Manyother biomolecular conformation changes could be driven in part by ergodic pumping. We suggest the use of ergodic pumping as a design principle in nanobiotechnology. |
03/03/2006 | |

Interaction of two charges in a uniform magnetic field I: planar problem P/06/10 Voir plus > Voir moins >The interaction of two charges moving in $R^2$ in a magnetic field ${f B}$ can be formulated as a hamiltonian system with 4 degrees of freedom. Assuming that the magnetic field is uniform and the interaction potential has rotational symmetry we reducethis Hamiltonian system to one with 2 degrees of freedom; for certain values of the conserved quantities and choices of parameters, we obtain an integrable system. Furthermore, when the interaction potential is of Coulomb type, we prove that, for suitableregime of parameters, there are invariant subsets on which this system contains a suspension of a subshift of finite type. This implies non-integrability for this system with a Coulomb-type interaction. Explicit knowledge of the reconstruction map and adynamical analysis of the reduced Hamiltonian systems are the tools we use in order to give a description for the various types fo dynamical behaviours in this system: from periodic ro quasiperiodic and chaotic orbits, from bounded to unbounded motion. |
03/03/2006 | |

Cerbelli and Giona's map is pseudo-Anosov and 9 consequences M/06/06 Voir plus > Voir moins >It is shown that a piecewise affine area-preserving homeomorphism of the 2-torus studied by Cerbelli and Giona is pseudo-Anosov. This enables one to prove various of their conjectures, quantify the multifractality of its "w-measures", calculate many other quantities for its dynamics, and construct an exact area-preserving tilt map of the cylinder with proved diffusive behaviour. |
10/02/2006 | |

Discommensuration Theory and Shadowing in Frenkel-Kontorova Models P/06/07 Voir plus > Voir moins >We prove that if the minimum energy advancing discommensuration of mean spacing $p/q$ for a Frenkel-Kontorova chain is unique up to translations and has phonon gap then all minimum energy states with mean spacing $\omega$ just above $p/q$ are approximated exponentially well in $q\omega - p$ by concatenations of advancing $p/q$ discommensuration. |
10/02/2006 | |

Dirichlet forms and Markov semigroups on non-associative vector bundles M/06/04 |
01/02/2006 | |

Sur quelques représentations potentiellement cristallines de $GL_2(Q_p)$ M/06/03 |
24/01/2006 | |

Jordan structures in harmonic functions and Fourier algebras on homogeneous spaces M/06/02 |
20/01/2006 | |

Bubbling Geometries for Half BPS Wilson lines P/06/01 |
18/01/2006 | |

Maximal surface group representations in isometry groups of classical Hermitian symmetric spaces M/05/51 |
21/12/2005 | |

On the geometry of moduli spaces of holomorphic chains over compact Riemann surfaces M/05/56 |
21/12/2005 | |

Universal enveloping algebras and some applications in physics P/05/26 Voir plus > Voir moins >These notes are intended to provide a self-contained and pedagogical introduction to the universal enveloping algebras and some of their uses in mathematical physics. After reviewing their abstract definitions and properties, the focus is put on their relevance in Weyl calculus, in representation theory and their appearance as higher symmetries of physical systems. |
20/12/2005 | |

Semi-global invariants of piecewise smooth Lagrangian fibrations M/05/55 Voir plus > Voir moins >We study certain types of piecewise smooth Lagrangian fibrations of smooth symplectic manifolds, which we call stitched Lagrangian fibrations. We extend the classical theory of action-angle coordinates to these fibrations by encoding the information on the non-smoothness into certain invariants consisting, roughly, of a sequence of closed 1-forms on a torus. The main motivation for this work is given by the piecewise smooth Lagrangian fibrations previously constructed by the authors, which topologicallycoincide with the local models used by Gross in "Topological Mirror Symmetry". |
20/12/2005 | |

Hidden symmetries and the fermionic sector of eleven-dimensional supergravity P/05/53 Voir plus > Voir moins >We study the hidden symmetries of the fermionic sector of D=11 supergravity, and the role of K(E10) as a generalised `R symmetry'. We find a consistent model of a massless spinning particle on an E10/K(E10) coset manifold whose dynamics can be mapped onto the fermionic and bosonic dynamics of D=11 supergravity in the near space-like singularity limit. This E10-invariant superparticle dynamics might provide the basis of a new definition of M-theory, and might describe the `de-emergence' of space-time near a cosmological singularity. |
15/12/2005 | |

On Killing tensors and cubic vertices in higher-spin gauge theories P/05/54 Voir plus > Voir moins >The problem of determining all consistent non-Abelian local interactions is reviewed in flat space-time. The antifield-BRST formulation of the free theory is an efficient tool to address this problem. Firstly, it allows to compute all on-shell local Killing tensor fields, which are important because of their deep relationship with higher-spin algebras. Secondly, under the sole assumptions of locality and Poincar?e invariance, all non-trivial consistent deformations of a sum of spin-three quadratic actions deforming the Abelian gauge algebra were determined. They are compared with lower-spin cases. |
15/12/2005 | |

Relative Seiberg-Witten and Ozsvath-Szabo invariants for surfaces in 4-manifolds M/05/57 Voir plus > Voir moins >We study the invariants of surfaces in 4-manifolds extracted from the Seiberg-Witten and the Ozsvath-Szabo invariants of their fiber sums with auxiliary Lefschetz fibrations. Such invariants involve relative Spin_c structures and can be treated as refinements of the usual Seiberg-Witten and Ozsvath-Szabo invariants. We prove several properties of the relative invariants, for instance the adjunction inequality for membranes, which estimates their genus, and the product formula. |
01/12/2005 | |

Topological strings and two dimensional electrons P/05/34 |
01/12/2005 | |

Collapsed 5-manifolds with pinched sectional curvature M/05/52 Voir plus > Voir moins >Let $M$ be a closed $5$-manifold of pinched curvature $0<\delta\le \text{sec}_M\le 1$. We prove that $M$ is homeomorphic to a spherical space form if $M$ satisfies one of the following conditions: (i) $\delta =1/4$ and the fundamental groupis a non-cyclic group of order $\ge C$, a constant. (ii) The center of the fundamental group has index $\ge w(\delta)$, a constant depending on $\delta$. (iii) The ratio of the volume and the maximal injectivity radius is $<\epsilon(\delta)$. (iv) The volume is less than $\epsilon(\delta)$ and the fundamental group $\pi_1(M)$ has a center of index at least $w$, a universal constant, and $\pi_1(M)$ is either isomorphic to a spherical $5$-space group or has an odd order. |
23/11/2005 | |

A Chiral Perturbation Expansion for Gravity P/05/48 |
22/11/2005 | |

Filtration de monodromie et cycles évanescents formels M/05/50 |
16/11/2005 | |

Refined Analytic Torsion as an Element of the Determinant Line M/05/49 Voir plus > Voir moins >We construct a canonical element, called the refined analytic torsion, of the determinant line of the cohomology of a closed oriented odd-dimensional manifold M with coefficients in a flat complex vector bundle E. We compute the Ray-Singer norm of the refined analytic torsion. In particular, if there exists a flat Hermitian metric on $E$, we show that this norm is equal to 1. We prove a duality theorem, establishing a relationship between the refined analytic torsions corresponding to a flat connection and its dual. |
08/11/2005 | |

Lectures on curved beta-gamma systems, pure spinors, and anomalies P/05/35 Voir plus > Voir moins >The curved beta-gamma system is the chiral sector of a certain infinite radius limit of the non-linear sigma model with complex target space. Naively it only depends on the complex structures on the worldsheet and the target space. It may suffer from theworldsheet and target space diffeomorphism anomalies. We analyze the curved beta-gamma system on the space of pure spinors, aiming to verify the consistency of Berkovits covariant superstring quantization. We demonstrate that under certain conditions bothanomalies can be cancelled for the pure spinor sigma model, in which case one reproduces the old construction of B.Feigin and E.Frenkel. |
02/11/2005 | |

On motives associated to graph polynomials M/05/46 Voir plus > Voir moins >The appearance of multiple zeta values in anomalous dimensions and $\beta$-functions of renormalizable quantum field theories has given evidence towards a motivic interpretation of these renormalization group functions. In this paper we start to hunt the motive, restricting our attention to a subclass of graphs in four dimensional scalar field theory which give scheme independent contributions to the above functions. |
11/10/2005 | |

On obstructions to asphericity of certain crossed modules M/05/45 |
11/10/2005 | |

Noncritical osp($1 vert 2$,R) M-theory matrix model with an arbitrary time dependent cosmological constant P/05/42 Voir plus > Voir moins >Dimensional reduction of the D=2 minimal super Yang-Mills to the D=1 matrix quantum mechanics is shown to double the number of dynamical supersymmetries, from N=1 to N=2. We analyze the most general supersymmetric deformation of the latter, in order to construct the noncritical 3D M-theory matrix model on generic supersymmetric backgrounds. It amounts to adding a harmonic oscillator potential with an arbitrary time dependent coefficient or cosmological `constant,' \Lambda(t). The resulting matrix modelenjoys, irrespective of \Lambda(t), two dynamical supersymmetries which further reveal three hidden so(1,2) symmetries. All together they form the supersymmetry algebra, osp(1|2,R). Each so(1,2) multiplet in the Hilbert space visualizes a dynamics constrained on either Euclidean or Minkowskian dS_{2}/AdS_{2} space, depending on its Casimir. In particular, all the unitary as well as BPS multiplets have the Euclidean dS_{2}/AdS_{2} geometry. We conjecture that the matrix model provides holographic duals tothe 2D superstring theories on various backgrounds having the spacetime signature Minkowskian if \Lambda(t)>0, or Euclidean if \Lambda(t)<0. In particular, we argue that the choice of the negative constant \Lambda corresponds to the N=2 super Liouvilletheory. |
11/10/2005 | |

Anatomy of a gauge theory P/05/40 Voir plus > Voir moins >Resumé: We exhibit the role of Hochschild cohomology in quantum field theory with particular emphasis on gauge theory and Dyson--Schwinger equations, the quantum equations of motion. These equations emerge from Hopf- and Lie algebra theory and free quantum field theory only. In the course of our analysis we exhibit an intimate relation between the Slavnov-Taylor identities for the couplings and the existence of Hopf sub-algebras defined on the sum of all graphs at a given loop order, surpassing the need to work on single diagrams. |
07/10/2005 | |

Théorie d'Iwasawa des représentations cristallines II M/05/41 |
07/10/2005 | |

Représentations modulaires de $mathrm{GL}_2(mathbf{Q}_p)$ et représentations galoisiennes de dimension $2$ M/05/44 Voir plus > Voir moins >On montre la conjecture de Breuil concernant la r\'eduction modulo $p$ des repr\'esentations triangulines $V$ et des repr\'esentations $\Pi(V)$ de $\mathrm{GL}_2(\mathbf{Q}_p)$ qui leur sont associ\'ees par la correspondance de Langlands $p$-adique. L'ingr\'edient principal de la d\'emonstration est l'\'etude de certaines repr\'esentations lisses irr\'eductibles de $\mathrm{B}(\mathbf{Q}_p)$ via des mod\`eles construits en utilisant les $(\varphi,\Gamma)$-modules. |
05/10/2005 | |

Kähler flat manifolds of low dimensions M/05/43 Voir plus > Voir moins >We give a list of six dimensional flat K\"ahler manifolds. Moreover, we present an example of eight dimensional flat K\"ahler manifold M with finite Out(\pi_1(M)) group. |
04/10/2005 | |

The Hopf algebra structure of renormalizable Quantum Field Theory P/05/39 Voir plus > Voir moins >Review for the Encyclopedia of Mathematical Physics. |
20/09/2005 | |

Quaternion Landau-Ginsburg models and noncommutative Frobenius manifolds M/05/37 Voir plus > Voir moins >We extend topological Landau-Ginsburg models with boundaries to Quaternion Landau-Ginsburg models that satisfy the axioms for open-closed topological field theories. Later we prove that moduli spaces of Quaternion Landau-Ginsburg models are non-commutative Frobenius manifolds in means of [J. Geom. Phys, 51 (2003),387-403.]. |
14/09/2005 | |

IR Free or Interacting? A Proposed Diagnostic P/05/38 |
14/09/2005 | |

The continuous spin limit of higher spin equations of motion P/05/36 Voir plus > Voir moins >We show that the Wigner equations describing the continuous spin representations can be obtained as a limit of massive higher-spin equations. The limit involves a suitable scaling of the wave function, the mass going to zero and the spin to infinity with their product being fixed. The result allows to transform the Wigner equations to a gauge invariant Fronsdal-like form. We also give the generalisation of the Wigner equations to higher dimensions with fields belonging to arbitrary representations of the massless little group. |
13/09/2005 | |

On non-commutative analytic spaces over non-archimedean fields M/05/33 Voir plus > Voir moins >We discuss various examples of non-commutative spaces which can be called non-commutative rigid analytic spaces |
30/08/2005 | |

On the torsion of optimal elliptic curves over function fields M/05/32 |
26/08/2005 | |

Torsion as a function on the space of representations M/05/30 |
16/08/2005 | |

Dynamics, Laplace transform and Spectral geometry M/05/31 |
16/08/2005 | |

Jean Dieudonné (1906-1992) mathematician M/05/28 Voir plus > Voir moins >Jean Dieudonn\'e has been one of the most influential French mathematicians during the 20$^{\rm th}$ century, especially through his association -- even identification -- with the Bourbaki group. An excellent biography has been written by his friend P. Dugac, a historian of science [4]. We shall retrace here his long and distinguished career. |
09/08/2005 | |

An algebraic proof of a cancellation theorem for surfaces M/05/29 Voir plus > Voir moins >Let $\K$ be an algebraically closed field of arbitrary characteristic. We give a short self-contained algebraic proof of the following statement: If the cylinder over an affine surface (i. e. the product of our surface and an affine line) over $\K$ is (isomorphic to) an affine space then the surface is (isomorphic to) an affine plane. |
09/08/2005 | |

Spin three gauge theory revisited P/05/25 Voir plus > Voir moins >We study the problem of consistent interactions for spin-$3$ gauge fields in flat spacetime of arbitrary dimension $n > 3$. Under the sole assumptions of Poincar\'e and parity invariance, local and perturbative deformation of the free theory, we determine all nontrivial consistent deformations of the abelian gauge algebra and classify the corresponding deformations of the quadratic action, at first order in the deformation parameter. We prove that all such vertices are cubic, contain a total ofeither three or five derivatives and are uniquely characterized by a rank-three constant tensor (an internal algebra structure constant). The covariant cubic vertex containing three derivatives is the vertex discovered by Berends, Burgers and van Dam, which however leads to inconsistencies at second order in the deformation parameter. In dimensions $n>4$ and for completely antisymmetric structure constant tensor, a new covariant cubic vertex exists, which contains five derivatives and passes the consistency test where the previous vertex failed. |
05/08/2005 | |

A group of diffeomorphisms of the interval with intermediate growth M/05/27 |
04/08/2005 | |

Sur la dynamique unidimensionnelle en régularité intermédiaire M/05/24 |
02/08/2005 | |

Représentations p-adiques ordinaires de GL2(Qp) et compatibilité local-global M/05/22 Voir plus > Voir moins >On définit les représentations p-adiques de GL2(Qp) "correspondant" aux représentations potentiellement cristallines réductibles (et éventuellement scindées) de Gal(Qpbar/Qp) de dimension 2 et on montre qu'elles apparaissent naturellement dans la cohomologie étale complétée de la tour en p des courbes modulaires. |
21/07/2005 | |

Représentations semi-stables de $GL_2 ({mathbb Q}_p)$, demi-plan $p$-adique et réduction modulo $p$ M/05/23 Voir plus > Voir moins >On calcule par voie cohomologique la r\'eduction modulo $p$ de certaines repr\'esentations $p$-adiques semi-stables de ${\rm GL}_2({\mathbb Q}_p)$. Les calculs exploitent la g\'eom\'etrie du demi-plan $p$-adique. Ils permettent de retrouver certaines formules de la r\'eduction modulo $p$ de repr\'esentations $p$-adiques semi-stables de ${\rm Gal}(\overline{\bf Q}_p/{\bf Q}_p)$. |
20/07/2005 | |

Cauchy-Davenport theorem in group extensions M/05/21 Voir plus > Voir moins >Let A and B be nonempty subsets of a finite group G in which the order of the smallest nontrivial subgroup is not smaller than d=|A|+|B|-1. Then the product set AB has at least d elements. This extends a classical theorem of Cauchy and Davenport to noncommutative groups. We also generalize Vosper's inverse theorem in the same spirit, giving a complete description of the critical pairs. The proofs depend on the structure of group extensions. |
13/07/2005 | |

Sur la conjecture faible de Greenberg dans le cas abélien $p$-décomposé M/05/20 Voir plus > Voir moins >Let $p$ be an odd prime. For any CM number field $K$ containing a primitive $p^{\rm th}$-root of unity, class field theory and Kummer theory put together yield the well known reflection inequality $\lambda^+ \leq \lambda^-$ between the ``plus'' and``minus'' parts of the $\lambda$-invariant of $K$. Greenberg's classical conjecture predicts the vanishing of $\lambda^+$. We propose a weak form of this conjecture: $\lambda^+ = \lambda^-$ if and only if $\lambda^+ = \lambda^- = 0$, and we proveit when $K^+$ is abelian, $p$ is totally split in $K^+$, and certain (mild) conditions on the cohomology of circular units are satisfied. |
13/07/2005 | |

On the Riemann zeta-function and analytic characteristic functions M/05/18 Voir plus > Voir moins >Set $f(s) :=1/(\sin(\pi s/4)q(1/2 + s))$ with $q(s) := \pi^{-s/2} \, 2 \Gamma (1 + s/2)(s-1) \zeta (s)$. The Riemann hypothesis, RH, and the simple zeros conjecture, SZC, together with conjectures advanced by the author are used to show that $f(s)$on each vertical strip $V_{4n}$ of $s$ with $4n < {\rm Re} \, (s) < 4(n+1)$ provides an analytic characteristic function, $(-1)^n \cdot f(s) = \int_R (dy) e^{sy} P_{4n} (y)$ with $P_{4n} (y)$ positive. The essential case with $n = 0$ implies RH. A formula is obtained for $P_{4n} (y)$, which for $y$ negative involves the critical zeros. An alternative formula is obtained for $P_{4n} (y)$, without relying on RH, SZC or other unproven conjectures. It does not involve the critical zeros. Analogous resultsfor the cases of the Dirichlet $L$-functions and the Ramanujan tau Dirichlet $L$-function are conjectured. |
28/06/2005 | |

Hopf algebras in renormalization theory: Locality and Dyson-Schwinger equations from Hochschild cohomology P/05/19 Voir plus > Voir moins >In this review we discuss the relevance of the Hochschild cohomology of renormalization Hopf algebras for local quantum field theories and their equations of motion. |
24/06/2005 | |

Semi-stable extensions on arithmetic surfaces M/05/17 Voir plus > Voir moins >On a given arithmetic surface, inspired by work of Miyaoka, we consider vector bundles which are extensions of a line bundle by another one. We give sufficient conditions for their restriction to the generic fiber to be semi-stable. We then apply the arithmetic analog of Bogomolov inequality in Arakelov theory, and deduce from it a lower bound for some successive minima in the lattice of extension classes between these line bundles. |
07/06/2005 | |

Estimates from below for the spectral function and for the remainder in local Weyl's law M/05/16 Voir plus > Voir moins >We obtain asymptotic lower bounds for the spectral function of the Laplacian and for the remainder in local Weyl's law on manifolds. In the negatively curved case, thermodynamic formalism is applied to improve the estimates. Key ingredients of the proof include the wave equation parametrix, a pretrace formula and the Dirichlet box principle. |
19/05/2005 | |

Formal Lagrangian Operad M/05/14 Voir plus > Voir moins >Given a symplectic manifold $M$, we may define an operad structure on the the spaces $\op^k$ of the Lagrangian submanifolds of $(\bar{M})^k\times M$ via symplectic reduction. If $M$ is also a symplectic groupoid, then its multiplication space is an associative product in this operad. Following this idea, we provide a deformation theory for symplectic groupoids analog to the deformation theory of algebras. It turns out that the semi-classical part of Kontsevich's deformation of $C^\infty(\R^d)$ is adeformation of the trivial symplectic groupoid structure of $T^*\R^d$. |
18/05/2005 | |

Gauge invariants and Killing tensors in higher-spin gauge theories P/05/15 Voir plus > Voir moins >In free completely symmetric tensor gauge field theories on Minkowski space-time, all gauge invariant functions and Killing tensor fields are computed, both on-shell and off-shell. These problems are addressed in the metric-like formalisms. |
18/05/2005 | |

Partial wave expansion and Wightman positivity in conformal field theory P/05/13 Voir plus > Voir moins >A new method for computing exact conformal partial wave expansions is developed and applied to approach the problem of Hilbert space (Wightman) positivity in a non-perturbative four-dimensional quantum field theory model. The model is based on the assumption of global conformal invariance on compactified Minkowski space (GCI). Bilocal fields arising in the harmonic decomposition of the operator product expansion (OPE) prove to be a powerful instrument in exploring the field content. In particular,in the theory of a field $\LL$ of dimension 4 which has the properties of a (gauge invariant) Lagrangian, the scalar field contribution to the 6-point function of the twist 2 bilocal field is analyzed with the aim to separate the free field part fromthe nontrivial part. |
26/04/2005 | |

Sur la réduction des représentations cristallines de dimension 2 en poids moyens M/05/12 Voir plus > Voir moins >On calcule la r\'eduction modulo $p$ des repr\'esentations cristallines de dimension $2$ dont les poids de Hodge-Tate sont $0$ et $k-1$ avec $k \in \{p+2,\cdots,2p-1\}$. |
20/04/2005 | |

On the Hochschild-Kostant-Rosenberg map for graded manifolds M/05/10 Voir plus > Voir moins >We show that the Hochschild--Kostant--Rosenberg map from the space of multivector fields on a graded manifold $N$ (endowed with a Berezinian volume) to the cohomology of the algebra of multidifferential operators on $N$ (as a subalgebra of the Hochschild complex of $C^\infty(N)$) is an isomorphism of Batalin--Vilkovisky algebras. Moreover, with an example inspired by string topology, we prove that in general the inclusion of multidifferential operators in the Hochschild complex is not a quasi-isomorphism. |
15/04/2005 | |

Rota-Baxter Algebras, Dendriform Algebras and Poincare-Birkhoff-Witt Theorem M/05/11 Voir plus > Voir moins >Rota-Baxter algebras appeared in both the physics and mathematics literature. It is of great interest to have a simple construction of the free object of this algebraic structure. For example, free commutative Rota-Baxter algebras relate to double shuffle relations for multiple zeta values. The interest in the non-commutative setting arose in connection with the work of Connes and Kreimer on the Birkhoff decomposition in renormalization theory in perturbative quantum field theory. We construct free non-commutative Rota-Baxter algebras and apply the construction to obtain universal enveloping Rota-Baxter algebras of dendriform dialgebras and trialgebras. We also prove an analog of the Poincare-Birkhoff-Witt theorem for universal enveloping algebra in the context of dendriform trialgebras. In particular, every dendriform dialgebra and trialgebra is a subalgebra of a Rota-Baxter algebra. We explicitly show that the free dendriform dialgebras and trialgebras, as represented by planar trees, are canonical subalgebras of free Rota-Baxter algebras. |
15/04/2005 | |

The character of pure spinors P/05/01 |
14/04/2005 | |

Dynamics of higher spin fields and tensorial space P/05/06 |
14/04/2005 | |

Biorthogonal Laurent polynomials, Töplitz determinants, minimal Toda orbits and isomonodromic tau functions M/05/08 Voir plus > Voir moins >We consider the class of biorthogonal polynomials that are used to solve the inverse spectral problem associated to elementary co-adjoint orbits of the Borel group of upper triangular matrices; these orbits are the phase space of generalizedintegrable lattices of Toda type. Such polynomials naturally interpolate between the theory of orthogonal polynomials on the line and orthogonal polynomials on the unit circle and tie together the theory of Toda, relativistic Toda, Ablowitz-Ladikand Volterra lattices. We establish corresponding Christoffel-Darboux formul\ae . For all these classes of polynomials a $2\times 2$ system of Differential-Difference-Deformation equations is analyzed in the most general setting of pseudomeasures with arbitrary rational logarithmic derivative. They provide particular classes of isomonodromic deformations of rational connections on the Riemann sphere. The corresponding isomonodromic tau function is explicitly related to the shifted T\"oplitz determinants of the moments of the pseudo-measure. In particular, the results imply that any (shifted) T\"oplitz (H\"ankel) determinant of a symbol (measure) with arbitrary rational logarithmic derivative is an isomonodromic taufunction. |
14/04/2005 | |

On the Distribution of the Wave Function for Systems in Thermal Equilibrium P/05/09 Voir plus > Voir moins >A density matrix that is not pure can arise, via averaging, from many different distributions of the wave function. This raises the question, which distribution of the wave function, if any, should be regarded as corresponding to systems in thermal equilibrium as represented, for example, by the density matrix $\rho_\beta = (1/Z) \exp(- \beta H)$ of the canonical ensemble. To answer this question, we construct, for any given density matrix $\rho$, a measure on the unit sphere in Hilbert space, denoted GAP($\rho$), using the Gaussian measure on Hilbert space with covariance $\rho$. We argue that GAP($\rho_\beta$) corresponds to the canonical ensemble. |
14/04/2005 | |

An invariant for non simply connected manifolds M/05/07 Voir plus > Voir moins >For a closed manifold $M$ we introduce the set of co-Euler structures and we define the modified Ray-Singer torsion, a positive real number associated to $M,$ a co-Euler structure and an acyclic representation $\rho$ of the fundamental group of $M$ with $H^\ast(M;\rho)=0.$ If the co-Euler structure is integral we show that the modified Ray--Singer torsion, regarded as a positive (real valued) function on the variety of some complex representations, is the absolute value of a (complex valued) rational function which carries interesting topological information about the manifold. This rational function is the invariant in the title. If the co-Euler structure is arbitrary one obtains a more general object, a holomorphic 1-cocycle. Interesting rational functions in topology appear in this way.The argument of this rational function when defined, is an interesting and apparently unexplored invariant which reminds the Atiyah--Patodi--Singer eta invariant. |
02/02/2005 | |

Uniform uniformisation M/05/03 |
01/02/2005 | |

Factorization Conjecture and the Open/Closed String Correspondence P/05/04 |
01/02/2005 | |

Analyticity of the susceptibility function for unimodal Markovian maps of the interval P/05/05 |
01/02/2005 | |

Semi-stable reduction of fiolations M/05/02 |
26/01/2005 | |

Gromov-Witten invariants and pseudo symplectic capacities M/04/60 Voir plus > Voir moins >We introduce the concept of pseudo symplectic capacities which is a mild generalization of that of symplectic capacities. As a generalization of the Hofer-Zehnder capacity we construct a Hofer-Zehnder type pseudo symplectic capacity and estimate itin terms of Gromov-Witten invariants. The (pseudo) symplectic capacities of Grassmannians and some product symplectic manifolds are computed. As applications we first derive some general nonsqueezing theorems that generalize and unite many previous versions, then prove the Weinstein conjecture for cotangent bundles over a large class of symplectic uniruled manifolds (including the uniruled manifolds in algebraic geometry) and also show that the Hofer-Zehnder capacity is finite on a small neighborhood of a rational connected closed symplectic submanifold of codimension two in a symplectic manifold. Finally, we give two results on symplectic packings in Grassmannians and on Seshadri constants. |
24/12/2004 | |

A LA RECHERCHE DE LA m-THÉORIE PERDUE Z-THEORY: CHASING m/f THEORY P/04/52 |
23/12/2004 | |

LECTURES ON NONPERTURBATIVE ASPECTS OF SUPERSYMMETRIC GAUGE THEORIES P/04/53 |
23/12/2004 | |

FROM SUPERSTRINGS TO QUANTUM FOAM USING SUPERSYMMETRY P/04/54 |
23/12/2004 | |

GROMOV-WITTEN THEORY AND DONALDSON-THOMAS THEORY, II M/04/55 |
23/12/2004 | |

Global geometric deformations of current algebras as Krichever-Novikov type algebras M/04/56 Voir plus > Voir moins >We construct algebraic-geometric families of genus one (i.e. elliptic) current and affine Lie algebras of Krichever-Novikov type. These families deform the classical current, respectively affine Kac-Moody Lie algebras. The construction is induced by the geometric process of degenerating the elliptic curve to singular cubics. If the finite-dimensional Lie algebra defining the infinite dimensional current algebra is simple then, even if restricted to local families, the constructed families are non-equivalent to the trivial family. In particular, we show that the current algebra is geometrically not rigid, despite its formal rigidity. This shows that in the infinite-dimensional Lie algebra case the relations between geometric deformations, formal deformations and Lie algebra two-cohomology are not that close as in the finite-dimensional case. The constructed families are e.g. of relevance in the global operator approach to the Wess-Zumino-Witten-Novikov models appearing in the quantization of Conformal Field Theory. |
23/12/2004 | |

Vertex algebras and the Landau-Ginzburg/Calabi-Yau correspondence M/04/57 Voir plus > Voir moins >We construct a spectral sequence that converges to the cohomology of the chiral de Rham complex over a Calabi-Yau hypersurface and whose first term is a vertex algebra closely related to the Landau-Ginzburg orbifold. As an application, we prove an explicit orbifold formula for the elliptic genus of Calabi-Yau hypersurfaces. |
23/12/2004 | |

On the Galois cohomology of unipotent algebraic groups over local and global function fields M/04/58 Voir plus > Voir moins >We discuss some results on the triviality and finiteness for Galois cohomology of connected unipotent groups over local and global function fields, and their relation with the closedness of orbits. As application, we show that a separable additive polynomial over a global field $k$ of characteristic $p>0$ in two variables is universal over $k$ if and only if it is so over all completions $k_v$ of $k$. |
05/12/2004 | |

Nonlinear Higher Spin Theories in Various Dimensions P/04/47 |
01/12/2004 | |

Some Rationality Properties of Observable Groups and Related Questions M/04/62 |
01/12/2004 | |

Chiral polyhedra in ordinary space, II M/04/61 Voir plus > Voir moins >A chiral polyhedron has a geometric symmetry group with two orbits on the flags, such that adjacent flags are in distinct orbits. Part I of the paper described the discrete chiral polyhedra in ordinary Euclidean 3-space with finite skew faces and finite skew vertex-figures. Part II completes the enumeration of all discrete chiral polyhedra in 3-space. There exist several families of chiral polyhedra with infinite, helical faces. In particular, there are no discrete chiral polyhedra with finite faces in addition to those described in Part I. |
01/12/2004 | |

EXPLICIT MUMFORD ISOMORPHISM FOR HYPERELLIPTIC CURVES M/04/51 Voir plus > Voir moins >We give an explicit version of the Mumford isomorphism on the moduli stack of hyperelliptic curves of any given genus. |
16/11/2004 | |

LA MONODROMIE HAMILTONIENNE DES CYCLES ÉVANESCENTS M/04/50 Voir plus > Voir moins >Nous montrons sous des hypoth\`eses pr\'ecis\'ees dans l'\'enonc\'e que le premier groupe d'homologie \'evanescente d'une fibration lagrangienne singuli\`ere est librement engendr\'e par les cycles \'evanescents. Nous en d\'eduisons que l'op\'erateur de variation associ\'e est un isomorphisme. |
05/11/2004 | |

Four basic symmetry types in the universal 7-cluster structure of 143 complete bacterial genomic sequences M/04/49 |
28/10/2004 | |

Fermions in the harmonic potential and string theory P/04/41 Voir plus > Voir moins >We explicitly derive collective field theory description for the system of fermions in the harmonic potential. This field theory appears to be a coupled system of free scalar and (modified) Liouville field. This theory should be considered as an exact bosonization of the system of non-relativistic fermions in the harmonic potential. Being surprisingly similar to the world-sheet formulation of c=1 string theory, this theory has quite different physical features and it is conjectured to give space-time description of the string theory, dual to the fermions in the harmonic potential. A vertex operator in this theory is shown to be a field theoretical representation of the local fermion operator, thus describing a D0 brane in the string language. Possible generalization of this result and its derivation for the case of c=1 string theory (fermions in the inverse harmonic potential) is discussed. |
28/10/2004 | |

Creation of Toy Universe P/04/48 Voir plus > Voir moins >General ideas of gauge/gravity duality allow for the possibility of time dependent solutions that interpolate between a perturbative gauge theory phase and a weakly curved string/gravity phase. Such a scenario applied to cosmology would exhibit a non-geometric phase before the big bang. We investigate a toy model for such a cosmology, whose endpoint is the classical limit of the two-dimensional non-critical string. We discuss the basic dynamics of this model, in particular how it evolves toward the double scaling limit required for stringy dynamics. We further comment on the physics that will determine the fluctuation spectrum of the scalar tachyon. Finally, we discuss various features of this model, and what relevance they might have for a more realistic, higher dimensional scenario. |
18/10/2004 | |

REPRÉSENTATIONS CRISTALLINES IRRÉDUCTIBLES DE ${ M/04/46 Voir plus > Voir moins >Nous démontrons certaines conjectures (non nullit\'e, irr\'eductibilit\'e topologique, admissibilit\'e) dues au second auteur concernant des représentations unitaires de GL2(Qp) sur des espaces de Banach p-adiques associées aux représentations cristallines irréductibles de dimension 2 de Gal(Qpbar/Qp). Pour cela, nous réinterprétons ces espaces de Banach comme espaces de fonctions sur Qp d'un certain type, puis nous utilisons la théorie des (phi,Gamma)-modules associés aux représentations cristallines correspondantes. |
05/10/2004 | |

Boundary Liouville theory at $c=1$ P/04/42 Voir plus > Voir moins >The c=1 Liouville theory has received some attention recently as the Euclidean version of an exact rolling tachyon background. In an earlier paper it was shown that the bulk theory can be identified with the interacting c=1 limit of unitary minimal models. Here we extend the analysis of the c=1-limit to the boundary problem. Most importantly, we show that the FZZT branes of Liouville theory give rise to a new 1-parameter family of boundary theories at c=1. These models share many features with the boundary Sine-Gordon theory, in particular they possess an open string spectrum with band-gaps of finite width. We propose explicit formulas for the boundary 2-point function and for the bulk-boundary operator product expansion in the c=1 boundary Liouville model. As a by-product of our analysis we also provide a nice geometric interpretation for ZZ branes and their relation with FZZT branes in the c=1 theory. |
29/09/2004 | |

On the Landau Background Gauge Fixing and the IR Properties of YM Green Functions P/04/23 Voir plus > Voir moins >We analyse the complete algebraic structure of the background field method for Yang--Mills theory in the Landau gauge and show several structural simplifications within this approach. In particular we present a new way to study the IR behavior of Green functions in the Landau gauge and show that there exists a unique Green function whose IR behaviour controls the IR properties of the gluon and the ghost propagators. |
29/09/2004 | |

Towards Integrability of Topological Strings I: Three-forms on Calabi-Yau manifolds P/04/43 Voir plus > Voir moins >The precise relation between Kodaira-Spencer path integral and a particular wave function in seven dimensional quadratic field theory is established. The special properties of three-forms in 6d, as well as Hitchin's action functional, play an important role. The latter defines a quantum field theory similar to Polyakov's formulation of 2d gravity; the curious analogy with world-sheet action of bosonic string is also pointed out. |
29/09/2004 | |

THE K-THEORY OF HEEGAARD-TYPE QUANTUM 3-SPHERES M/04/44 Voir plus > Voir moins >We use a Heegaard splitting of the topological 3-sphere as a guiding principle to construct a family of its noncommutative deformations. The main technical point is an identification of the universal C*-algebras defining our quantum 3-spheres with an appropriate fiber product of crossed-product C*-algebras. Then we employ this result to show that the K-groups of our family of noncommutative 3-spheres coincide with their classical counterparts. |
29/09/2004 | |

Lattice Geometry P/04/45 |
29/09/2004 | |

The Structure of the Ladder Insertion-Elimination Lie Algebra M/04/40 Voir plus > Voir moins >We continue our investigation into the insertion-elimination Lie algebra of Feynman graphs in the ladder case, emphasizing the structure of this Lie algebra relevant for future applications in the study of Dyson-Schwinger equations. We work out the relation of this Lie algebra to some classical infinite dimensional Lie algebra and we determine its cohomology. |
01/09/2004 | |

Saddle point equations in Seiberg-Witten theory P/04/38 Voir plus > Voir moins >N=2 supersymmetric Yang-Mills theories for all classical gauge groups, that is, for SU(N), SO(N), and Sp(N) is considered. The equations which define the Seiberg-Witten curve are proposed. In some cases they are solved. It is shown that for (almost) all models allowed by the asymptotic freedom the 1-instanton corrections which follows from these equations agree with the direct computations and with known results. |
24/08/2004 | |

What is the trouble with Dyson--Schwinger equations? P/04/37 Voir plus > Voir moins >We discuss similarities and differences between Green Functions in Quantum Field Theory and polylogarithms. Both can be obtained as solutions of fixpoint equations which originate from an underlying Hopf algebra structure. Typically, the equation is linear for the polylog, and non-linear for Green Functions. We argue though that the crucial difference lies not in the non-linearity of the latter, but in the appearance of non-trivial representation theory related to transcendental extensions of the number field which governs the linear solution. An example is studied to illuminate this point. |
11/08/2004 | |

Spitzer's identity and the algebraic Birkhoff decomposition in pQFT P/04/39 Voir plus > Voir moins >In this article we continue to explore the notion of Rota-Baxter algebras in the context of the Hopf algebraic approach to renormalization theory in perturbative quantum field theory. We show in very simple algebraic terms that the solutions of the recursively defined formulae for the Birkhoff factorization of regularized Hopf algebra characters, i.e. Feynman rules, naturally give a non-commutative generalization of the well-known Spitzer's identity. The underlying abstract algebraic structure is analyzed in terms of complete filtered Rota-Baxter algebras. |
11/08/2004 | |

Approximation by analytic operator functions. Factorizations and very badly approximable functions M/04/36 Voir plus > Voir moins >This is a continuation of our earlier paper. We consider here operator-valued functions (or infinite matrix functions) on the unit circle $\T$ and study the problem of approximation by bounded analytic operator functions. We discuss thematic and canonical factorizations of operator functions and study badly approximable and very badly approximable operator functions. We obtain algebraic and geometric characterizations of badly approximable and very badly approximable operator functions. Note that there is an important difference between the case of finite matrix functions and the case of operator functions. Our criteria for a function to be very badly approximable in the case of finite matrix functions also guarantee that the zero function is the only superoptimal approximant. However in the case of operator functions this is not true. |
11/08/2004 | |

AN EXTENSION OF THE KOPLIENKO-NEIDHARDT TRACE FORMULAE M/04/35 Voir plus > Voir moins >Koplienko found a trace formula for perturbations of self-adjoint operators by operators of Hilbert Schmidt class $\bS_2$. A similar formula in the case of unitary operators was obtained by Neidhardt. In this paper we improve their results and obtain sharp conditions under which the Koplienko--Neidhardt trace formulae hold. |
30/07/2004 | |

Bethe Ansatz for Arrangements of Hyperplanes and the Gaudin Model M/04/34 Voir plus > Voir moins >We show that the Shapovalov norm of a Bethe vector in the Gaudin model is equal to the Hessian of the logarithm of the corresponding master function at the corresponding isolated critical point. We show that different Bethe vectors are orthogonal. These facts are corollaries of a general Bethe ansatz type construction, suggested in this paper and associated with an arbitrary arrangement of hyperplanes. |
29/07/2004 | |

Differentiating the absolutely continuous invariant measure of an interval map $f$ with respect to $f$ M/04/32 |
23/07/2004 | |

Differentiation of SRB states for hyperbolic flows M/04/33 |
23/07/2004 | |

ABCD of instantons P/04/19 Voir plus > Voir moins >We solve N=2 supersymmetric Yang-Mills theories for arbitrary classical gauge group, i.e. SU(N), SO(N), Sp(N). In particular, we derive the prepotential of the low-energy effective theory, and the corresponding Seiberg-Witten curves. We manage to do thiswithout resolving singularities of the compactified instanton moduli spaces. |
21/07/2004 | |

Bernoulli Number Identities from Quantum Field Theory P/04/31 Voir plus > Voir moins >We present a new method for the derivation of convolution identities for finite sums of products of Bernoulli numbers. Our approach is motivated by the role of these identities in quantum field theory and string theory. We first show that the Miki identity and the Faber-Pandharipande-Zagier (FPZ) identity are closely related, and give simple unified proofs which naturally yield a new Bernoulli number convolution identity. We then generalize each of these three identities into new families ofconvolution identities depending on a continuous parameter. We rederive a cubic generalization of Miki's identity due to Gessel and obtain a new similar identity generalizing the FPZ identity. The generalization of the method to the derivation of convolution identities of arbitrary order is outlined. We also describe an extension to identities which relate convolutions of Euler and Bernoulli numbers. |
29/06/2004 | |

Holomorphically Covariant Matrix Models P/04/30 Voir plus > Voir moins >We present a method to construct matrix models on arbitrary simply connected oriented real two dimensional Riemannian manifolds. The actions and the path integral measure are invariant under holomorphic transformations of matrix coordinates. |
28/06/2004 | |

Distance Function, Linear quasi-Connections and Chern Character. M/04/27 Voir plus > Voir moins >In Sect.4 we show how the Chern character of the tangent bundle of a smooth manifold may be extracted from the geodesic distance function by means of cyclic homology. In Sect.5 we introduce the notion of coarse linear connection in vector bundles, notion which generalizes the notion of linear connection. We show next that the algebraic procedure for constructing the Chern character, discussed in Sect.4, applies also in the case of coarse linear connections. Looking in retrospect, the constructions we present here represent the non commutative counterpart of a geometric construction of the Chern character, see Teleman N.[Tn] and Teleman C.[Tc]. The arguments discussed here may be formulated within the language of groupoids. In a subsequent paper we are going to improve some of the considerations presented here and extend their field of application to more singular situations. |
25/06/2004 | |

Optimal Trade-Off for Merkle Tree Traversals M/04/29 Voir plus > Voir moins >We prove tight upper and lower bounds for computing Merkle tree traversals, and display optimal trade-offs between time and space complexity of that problem. |
17/06/2004 | |

Gravitational radiation from inspiralling compact binaries completed at the third post-Newtonian order P/04/25 Voir plus > Voir moins >The gravitational radiation from point particle binaries is computed at the third post-Newtonian (3PN) approximation of general relativity. Three previously introduced ambiguity parameters, coming from the Hadamard self-field regularization of the 3PN source-type mass quadrupole moment, are consistently determined by means of dimensional regularization, and proved to have the values xi = -9871/9240, kappa = 0 and zeta = -7/33. These results complete the derivation of the general relativistic prediction for compact binary inspiral up to 3.5PN order, and should be of use for searching and deciphering the signals in the current network of gravitational wave detectors. |
15/06/2004 | |

Mathematical models in population dynamics and ecology M/04/26 Voir plus > Voir moins >We introduce the most common quantitative approaches to population dynamics and ecology, emphasizing the different theoretical foundations and assumptions. These populations can be aggregates of cells, simple unicellular organisms, plants or animals. The basic types of biological interactions are analysed: consumer-resource, prey-predation, competition and mutualism. Some of the modern developments associated with the concepts of chaos, quasi-periodicity, and structural stability are discussed. To describe short- and long-range population dispersal, the integral equation approach is derived, and some of its consequences are analysed. We derive the standard McKendrick age-structured density dependent model, and a particular solution of theMcKendrick equation is obtained by elementary methods. The existence of demography growth cycles is discussed, and the differences between mitotic and sexual reproduction types are analysed. |
15/06/2004 | |

Approximation Hardness of Short Symmetric Instances of MAX-3SAT M/04/28 Voir plus > Voir moins >We prove approximation hardness of short symmetric instances of MAX-3SAT in which each literal occurs exactly twice, and each clause is exactly of size 3. We display also an explicit approximation lower bound for that problem. The bound two on the number of occurrences of literals in symmetric MAX-3SAT is thus the smallest possible bound for the MAX-3SAT hardness gap property to exist and making the instances hard to approximate. |
15/06/2004 | |

Deformation of outer representations of Galois group M/04/24 Voir plus > Voir moins >To a hyperbolic smooth curve defined over a number-field one naturally associates an "anabelian" representation of the absolute Galois group of the base field landing in outer automorphism group of the algebraic fundamental group. In this paper, weintroduce several deformation problems for Lie-algebra versions of the above representation and show that, this way we get a richer structure than those coming from deformations of "abelian" Galois representations induced by the Tate module of associated Jacobian variety. We develop an arithmetic deformation theory of graded Lie algebras with finite dimensional graded components to serve our purpose. |
02/06/2004 | |

Phasing of gravitational waves from inspiralling eccentric binaries P/04/22 Voir plus > Voir moins >We provide a method for analytically constructing high-accuracy templates for the gravitational wave signals emitted by compact binaries moving in inspiralling eccentric orbits. By contrast to the simpler problem of modeling the gravitational wave signals emitted by inspiralling {\it circular} orbits, which contain only two different time scales, namely those associated with the orbital motion and the radiation reaction, the case of {\it inspiralling eccentric} orbits involves {\it three different time scales}: orbital period, periastron precession and radiation-reaction time scales. By using an improved `method of variation of constants', we show how to combine these three time scales, without making the usual approximation of treating the radiativetime scale as an adiabatic process. We explicitly implement our method at the 2.5PN post-Newtonian accuracy. Our final results can be viewed as computing new `post-adiabatic' short period contributions to the orbital phasing, or equivalently, new short-period contributions to the gravitational wave polarizations, $h_{+,\times}$, that should be explicitly added to the `post-Newtonian' expansion for $h_{+,\times}$, if one treats radiative effects on the orbital phasing of the latter in the usual adiabatic approximation. Our results should be of importance both for the LIGO/VIRGO/GEO network of ground based interferometric gravitational wave detectors (especially if Kozai oscillations turn out to be significant in globular cluster triplets), and for thefuture space-based interferometer LISA. |
27/05/2004 | |

Conformal invariance and rationality in an even dimensional quantum field theory P/04/21 |
21/05/2004 | |

Vertex Operators for Closed Superstrings P/04/20 Voir plus > Voir moins >We construct an iterative procedure to compute the vertex operators of the closed superstring in the covariant formalism given a solution of IIA/IIB supergravity. The manifest supersymmetry allows us to construct vertex operators for any generic background in presence of Ramond-Ramond (RR) fields. We extend the procedure to all massive states of open and closed superstrings and we identify two new nilpotent charges which are used to impose the gauge fixing on the physical states. We solve iteratively theequations of the vertex for linear x-dependent RR field strengths. This vertex plays a role in studying non-constant C-deformations of superspace. Finally, we construct an action for the free massless sector of closed strings, and we propose a form for the kinetic term for closed string field theory in the pure spinor formalism. |
13/05/2004 | |

Self-similar Fractals in Arithmetic M/04/18 Voir plus > Voir moins >We define a notion of self-similarity on algebraic varieties by considering algebraic endomorphisms as "similarity" maps. Self-similar objects are called fractals, for which we present several examples and define a notion of dimension in many differentcontexts. We also present a strong version of Roth's theorem for algebraic points on a variety approximated by fractal elements. Fractals provide a framework in which one can unite several important conjectures in Diophantine geometry. |
30/04/2004 | |

The residues of quantum field theory - numbers we should know M/04/17 Voir plus > Voir moins >We discuss in an introductory manner structural similarities between the polylogarithm and Green functions in quantum field theory. |
20/04/2004 | |

Noncentral extension of the $AdS_{5} \times S^{5}$ superalgebra : supermultiplet of brane charges P/04/15 Voir plus > Voir moins >We propose an extension of the su(2, 2|4) superalgebra to incorporate the F1/D1 string charges in type IIB string theory on the $AdS_{5} \times S^{5}$ background, or the electro-magnetic charges in the dual super Yang-Mills theory. With the charges introduced, the superalgebra inevitably undergoes a noncentral extension, as noted recently in [1]. After developing a group theoretical method of obtaining the noncentral extension, we show that the charges form a certain nonunitary representation of the original unextended superalgebra, subject to some constraints. We solve the constraints completely and show that, apart from the su(2,2|4) generators, there exist 899 complex brane charges in the extended algebra. Explicitly we present all the super-commutation relations among them. |
18/04/2004 | |

D-brane charges on SO(3) P/04/14 Voir plus > Voir moins >In this letter we discuss charges of D-branes on the group manifold SO(3). Our discussion will be based on a conformal field theory analysis of boundary states in a Z_2-orbifold of SU(2). This orbifold differs from the one recently discussed by Gaberdieland Gannon in its action on the fermions and leads to a drastically different charge group. We shall consider maximally symmetric branes as well as branes with less symmetry, and find perfect agreement with a recent computation of the corresponding K-theory groups. |
12/04/2004 | |

Weak Bézout inequality for D-modules M/04/16 Voir plus > Voir moins >A bound is obtained on the leading coefficient of the Hilbert-Kolchin polynomial of a D-module in terms of the degrees of its generators. |
10/04/2004 | |

The Hopf algebra of rooted trees in Epstein-Glaser Renormalization P/04/12 Voir plus > Voir moins >We show how the Hopf algebra of rooted trees, in a somewhat modified presentation, encodes the combinatorics of Epstein-Glaser renormalization and position space renormalization in general. In particular we prove that the Epstein-Glaser time-ordered products can be obtained from the Hopf algebra by suitable Feynman rules, mapping trees to operator-valued distributions, and by twisting the antipode with a renormalization character, which formally solves the Bogoliubov recursion and provides local counterterms due to the Hochschild 1-closedness of the grafting operator $B_+$. |
01/04/2004 | |

S-duality and Topological Strings P/04/09 Voir plus > Voir moins >In this paper we show how S-duality of type IIB superstrings leads to an S-duality relating A and B model topological strings on the same Calabi-Yau as had been conjectured recently: D-instantons of the B-model correspond to A-model perturbative amplitudes and D-instantons of the A-model capture perturbative B-model amplitudes. Moreover this confirms the existence of new branes in the two models. As an application we explain the recent results concerning A-model topological strings on Calabi-Yau and its equivalence to the statistical mechanical model of melting crystal. |
31/03/2004 | |

Lusternik-Schnirelman theory and dynamics, II M/04/13 |
30/03/2004 | |

An introduction to arithmetic groups M/04/11 Voir plus > Voir moins >Arithmetic groups are groups of matrices with integral entries. We shall first discuss their origin in number theory (Gauss, Minkowski) and their role in the "reduction theory of quadratic forms". Then we shall describe these groups by generators and relations. The next topic will be: are all subgroups of finite index given by congruence conditions? Finally, we shall discuss rigidity properties of arithmetic groups. |
20/03/2004 | |

Integrable Renormalization II: the general case P/04/08 Voir plus > Voir moins >We extend the results we obtained in an earlier. The cocommutative case of rooted ladder graphs is generalized to a full Hopf algebra of (decorated) rooted trees. For Hopf algebra characters with target space of Rota-Baxter type, the Birkhoff decomposition of renormalization theory is derived by using the Rota-Baxter double construction, respectively Atkinson's theorem. We also outline the extension to the Hopf algebra of Feynman graphs via decorated rooted trees. |
17/03/2004 | |

Torsion cohomology classes and algebraic cycles on complex projective manifolds M/04/10 Voir plus > Voir moins >Atiyah and Hirzebruch gave examples of even degree torsion classes in the singular cohomology of a smooth complex projective manifold, which are not Poincaré dual to an algebraic cycle. We notice that the order of these classes are small compared to the dimension of the manifold. However, building upon a construction of Kollár, one can provide such examples with arbitrary high prime order, the dimension being fixed. This method also provides examples of torsion algebraic cycles, which are non trivial in the Griffiths' groups, and lie in a arbitrary high level of the H.Saito filtration on Chow groups. |
10/03/2004 | |

Systèmes de Taylor-Wiles pour ${\rm GSp}_4$ M/04/07 Voir plus > Voir moins >On montre qu'une représentation galoisienne symplectique de degré quatre congrue modulo p à une représentation galoisienne provenant d'une forme de Siegel de genre deux provient elle-même d'une telle forme de Siegel. On suppose pour cela que l'image de Galois est grosse modulo p et que des hypothèses locales sont satisfaites (minimalité en dehors de p et ordinarité cristalline en p, de poids de Hodge-Tate adéquats). On utilise pour cela la technique des systèmes de Taylor-Wiles. |
07/03/2004 | |

Classical/quantum integrability in AdS/CFT P/04/05 |
07/03/2004 | |

An inverse theorem for the restricted set addition in Abelian groups M/04/06 Voir plus > Voir moins >Let $A$ be a set of $k\ge 5$ elements of an Abelian group $G$ in which the order of the smallest nontrivial subgroup is larger than $2k-3$. Extending a result of Dias da Silva and Hamidoune (Bull. London Math. Soc. 26 (1994) 140-146), in a recent paperwe proved that the number of different elements of $G$ that can be written in the form $a+a'$, where $a, a'\in A$, $a\ne a'$, is at least $2k-3$. Here we prove that the bound is attained if and only if the elements of $A$ form an arithmetic progression in $G$, thus completing the solution of a problem of Erd\H os and Heilbronn. The proof is based on the so-called `Combinatorial Nullstellensatz'. |
25/02/2004 | |

Spectral Asymmetry, Zeta Functions and the Noncommutative Residue M/04/02 Voir plus > Voir moins >In this paper, motivated by an approach developped by Wodzicki, we look at the spectral asymmetry of elliptic PsiDO's in terms of theirs zeta functions. First, using asymmetry formulas of Wodzicki we study the spectral asymmetry of odd elliptic PsiDO'sand of geometric Dirac operators. In particular, we show that the eta function of a selfadjoint elliptic odd PsiDO is regular at every integer point when the dimension and the order have opposite parities (this generalizes a well known result of Branson-Gilkey for Dirac operators), and we relate the spectral asymmetry of a Dirac operator on a Clifford bundle to the Riemmanian geometric data, which yields a new spectral interpretation of the Einstein action from gravity. We also obtain a large class of examples of elliptic PsiDO's for which the regular values at the origin of the (local) zeta functions can easily be seen to be independent of the spectral cut. On the other hand, we simplify the proofs of two well-known and difficult results of Wodzicki: (i) The independence with respect to the spectral cut of the regular value at the origin of the zeta function of an elliptic PsiDO; (ii) The vanishing of the noncommutative residue of a zero'th order PsiDO projector. These results were proved by Wodzickiusing a quite difficult and involved characterization of local invariants of spectral asymmetry, which we can bypass here. Finally, in an appendix we give a new proof of the aforementioned asymmetry formulas of Wodzicki. |
30/01/2004 | |

The entropy of black holes: a primer P/04/04 Voir plus > Voir moins >After recalling the definition of black holes, and reviewing their energetics and their classical thermodynamics, one expounds the conjecture of Bekenstein, attributing an entropy to black holes, and the calculation by Hawking of the semi-classical radiation spectrum of a black hole, involving a thermal (Planckian) factor. One then discusses the attempts to interpret the black-hole entropy as the logarithm of the number of quantum micro-states of a macroscopic black hole, with particular emphasis on results obtained within string theory. After mentioning the (technically cleaner, but conceptually more intricate) case of supersymmetric (BPS) black holes and the corresponding counting of the degeneracy of Dirichlet-brane systems, one discusses in some detail the "correspondence" between massive string states and non-supersymmetric Schwarzschild black holes. |
21/01/2004 | |

Cayley-Hamilton Decomposition and Spectral Asymmetry M/04/01 Voir plus > Voir moins >In this paper we derive Cayley-Hamilton decompositions, along some of their consequences, for compact operators and closed operators with compact resolvent on a (separable) Hilbert space. In particular, we make use these decompositions to give a spectralinterpretation of a projector found by Wodzicki to encode the spectral asymmetry of elliptic PsiDO's on a compact manifold. As another application we get a convenient definition of the partial inverse of a closed operator with compact resolvent. Finally,we work out the results of this paper in the examples of an elliptic PsiDO on a compact manifold and of an elliptic PsiDO on a spectral triple (i.e. on a noncommutative manifold in the sense of Connes's noncommutative geometry). |
20/01/2004 | |

Unraveling the Fourier Law for Hamiltonian Systems P/04/03 Voir plus > Voir moins >We exhibit simple Hamiltonian and stochastic models of heat transport in non-equilibrium problems. Theoretical arguments are given to show that, for a wide class of models, the temperature profile obeys a universal law depending on a parameter $\alpha $. When $\alpha=1$, the law is linear, but, depending on the nature of the energy exchange mechanism by tracer particles, we find that $\alpha $ is, in many cases, different from $1$. When $\alpha \neq 1$, the temperature profile is not linear, although translation invariance and, in some models, local thermal equilibrium, hold. |
14/01/2004 |