Séminaire de géométrie arithmétique

Faltings’ approach in p-adic Hodge theory can be schematically divided into two main steps: firstly, a local reduction of the computation of the p-adic étale cohomology of a smooth variety over a p-adic local field to a Galois cohomology computation and then, the establishment of a link between the latter and differential forms. These relations are organized through Faltings ringed topos whose definition relies on the choice of an integral model of the variety, and whose good properties depend on the (logarithmic) smoothness of this model. Scholze’s generalization for rigid analytic varieties has the advantage of depending only on the variety (i.e. the generic fibre). Inspired by Deligne’s approach to classical Hodge theory for singular varieties, we establish a cohomological descent result for the structural sheaf of Faltings topos, which makes it possible to extend Faltings’ approach to any integral model, i.e. without any smoothness assumption. An essential ingredient of our proof is a descent result of perfectoid algebras in the arc-topology due to Bhatt and Scholze. 

As an application of our cohomological descent, using a variant of de Jong’s alteration theorem for morphisms of schemes due to Gabber-Illusie-Temkin, we generalize Faltings’ main p-adic comparison theorem to any proper and finitely presented morphism of coherent schemes over an absolute integral closure of Z_p (without any assumption of smoothness) for torsion étale sheaves (not necessarily finite locally constant). As a second application, we deduce a local version of the relative Hodge-Tate filtration from the global version constructed by Abbes-Gros.

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Two hyperbolic surfaces are said to be (length) isospectral if they have the same collection of lengths of primitive closed geodesics, counted with multiplicity (i.e. if they have the same length spectrum). For closed surfaces, there is an upper bound on the size of isospectral hyperbolic structures depending only on the topology. We will show that the situation is very different for infinite-type surfaces, by constructing large families of isospectral hyperbolic structures on surfaces of infinite genus.

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In this talk I will  present a general construction in terms of Higgs bundles of the higher Teichmüller components of the character variety of a surface group for a real Lie group admitting a positive structure in the sense of Guichard-Wienhard. Key ingredients in this construction are the notion of magical sl2-triple, that we introduce, and the Cayley correspondence. Basics on Higgs bundle theory will be explained.
(Based on joint work with Bradlow, Collier, Gothen and Oliveira).

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In this seminar I will briefly review some success stories of Machine Learning applied to bio-medical domain up to date and speculate on what it will take to enable a much more substantial progress. I will specifically discuss Biology of Aging – the field which remains most promising and most fraudulent over the thousands of years in history of medical sciences. I will present my own work and suggest where theoretical approaches and modeling can make a big difference in a search for anti-aging and rejuvenating interventions.

More information:

 A recent interview with Longevity Technology on Radically Open Science platform

    https://www.longevity.technology/a-better-model-organism-for-testing-antiaging-drugs/

An interview with Llifespan.io on the state of aging science, Peshkin’s approaches and Machine Learning for Biology of Aging

     https://www.lifespan.io/news/an-interview-with-dr-leonid-peshkin/

   A 3 min video on Daphnia as a novel model organism for aging:

     https://vimeo.com/386647406

A preprint on Smart Tanks platform
     https://www.biorxiv.org/content/10.1101/2021.05.30.446339v1

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The variational method is a powerful approach to solve many-body quantum problems non perturbatively. However, in the context of relativistic quantum field theory (QFT), it needs to meet 3 seemingly incompatible requirements outlined by Feynman: extensivity, computability, and lack of UV sensitivity. In practice, variational methods usually break one of the 3, which translates into the need to have an IR or UV cutoff. I will explain how a relativistic modification of continuous matrix product states allows us to satisfy the 3 requirements jointly in 1+1 dimensions. Optimizing over this class of states, one can solve scalar QFT without UV cutoff and directly in the thermodynamic limit, and numerics are promising. I will try to cover both the general philosophy of the method, the basics of the computations, and mention the many open problems.

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Séminaire Laurent Schwartz — EDP et applications

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Séminaire Laurent Schwartz — EDP et applications

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IHES Covid-19 regulations:

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and where the social distancing is not possible;
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==================================================================

Séminaire Laurent Schwartz — EDP et applications

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IHES Covid-19 regulations:

– all the participants who will attend the event in person will have to keep their mask on in indoor spaces
and where the social distancing is not possible;
– speakers will be free to wear their mask or not at the moment of their talk if they feel more comfortable
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– Over 25 persons in the conference room, every participant will be asked to provide a health pass which will
be checked at the entrance of the conference room.

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In the Heisenberg picture of quantum mechanics, time evolution is a one-parameter family of automorphisms of operator algebra. Restricted to short times the equivalence between time evolution and quantum circuits, especially the property that it maps a local operator to another, has been implanted in theoretical studies of topological phases of matter. In this talk, I will explain recent findings that not all locality-preserving automorphisms, also called quantum cellular automata, can be written as quantum circuits — there exists a « discrete time dynamics » that cannot have a « Hamiltonian. » These are tightly related to static, topological many-body states. I will give results on the classification of these automorphisms, and connect them to locally generated subalgebras in one lower dimension.

Participer à la réunion Zoom
https://us02web.zoom.us/j/83786264059?pwd=Nk81UDhlT3JLSDFkd29KY0NUMFYvZz09

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We find that several non-integrable systems exhibit some exact eigenstates that span the energy spectrum from lowest to the highest state. In the AKLT Hamiltonian and in several others “special” non-integrable models, we are able to obtain the analytic expression of states exactly and to compute their entanglement spectrum and entropy to show that they violate the eigenstate thermalization hypothesis. This represented the first example of ETH violation in a non-integrable system; these types  of states have gained notoriety since then as quantum Scars in the context of Rydberg atoms experiments. We furthermore show that the structure of these states, in most models where they are found is that of an almost spectrum generating algebra which we call Restricted Spectrum Generating Algebra. This includes the (extended) Hubbard model, as well as some thin-torus limits of Fractional Quantum Hall states. Yet in other examples, such as the recently found chiral non-linear luttinger liquid, their structure is more complicated and not understood.

Participer à la réunion Zoom
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The Berry phase is a well-known phenomenon in quantum mechanics with many profound implications. It describes the response of the phase of the wavefunction to the adiabatic evolution of system parameters, defining a U(1) connection on the parameter space. In many-body systems described by quantum field theory, we may also allow the parameters to vary in space, and we find a higher group connection generalizing the Berry phase. This connection also describes phenomena such as the Thouless pump and its generalizations. It allows us to constrain the global structure of phase diagrams by probing non-contractible cycles in the space of quantum field theories. In a typical phase diagram drawn in R^n, these cycles surround topologically-protected critical loci called diabolical points, in analogy to the quantum mechanical singularities which act as « monopoles » for the Berry connection. I will discuss these concepts in more detail, as well as a bulk-boundary correspondence and some recent applications to phase diagrams of topologically ordered systems. This talk is based on https://arxiv.org/abs/2004.10758 w/ Po-Shen Hsin and Anton Kapustin https://arxiv.org/abs/2110.07599 and its sequel, 2110.xxxx w/ Nathanan Tantivasadakarn, Ashvin Vishwanath, and Ruben Verresen.

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https://us02web.zoom.us/j/87445066109?pwd=U1Bjc211enZlOGFYd0l5REltRWVqQT09

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Emergence is a major buzz word of our times. My working definition, which gives plenty of room for manoeuvre is: the appearance of many body phenomena of higher symmetry than that of the Hamiltonian and degrees of freedom at the microscopic level.

In this colloquium I will discuss a topical example – the frustrated magnetic material, spin ice. Here, to an excellent approximation a classical field theoretic description with continuous U(1) symmetry emerges from Ising like degrees of freedom. The associated quasi-particles appear to be freely moving magnetic charge – magnetic monopoles – and the system behaves as a magnetic Coulomb fluid in the grand canonical ensemble with intrinsic topological properties. With the addition of quantum fluctuations the emergent magneto-statics develops further into a complete analogue of quantum electrodynamics. I will aliment this discussion with experimental results from a wide range of systems.

https://us02web.zoom.us/j/85270888147?pwd=aXdOVXBTSmNEU00vVFE2bXhqdE5vdz09

ID de réunion : 852 7088 8147
Code secret : 276852