We introduce generalized pinning fields in conformal field theory that model a large class of critical impurities at large distance, enriching the familiar universality classes. We provide a rigorous definition of such defects as certain unbounded operators on the Hilbert space and prove that when inserted on codimension-one surfaces they factorize the spacetime into two halves. The possible factorization channels are further constrained by symmetries in the bulk. As a corollary, we solve such critical impurities in the 2d tricritical Ising model and establish the factorization phenomena previously observed for localized mass deformations in the 3d O(N) model. If time permits, I will also explore the characteristics of these defects, including their density of states and the asymptotic behavior of one-point functions.
 
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Running Seminar
 
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The aim of this workshop is to bring together mathematicians and computer scientists around some talks on recent results from statistics, machine learning, and more generally data science research. Various topics in machine learning, optimization, deep learning, optimal transport, fairness, statistics will be presented. This workshop is particularly intended for doctoral and post-doctoral researchers.
 
Registration is free and open until March 25, 2025.
Invited speakers:Anne Auger (Inria Saclay)Etienne Boursier (Inria, Université Paris-Saclay)Solenne Gaucher (École polytechnique)Charlotte Laclau (Télécom Paris)Arshak Minasyan (CentraleSupélec)Nicolas Vayatis (ENS Paris-Saclay)
Organizers: Evgenii Chzhen (Laboratoire de Mathématiques d’Orsay, Université Paris-Saclay)Erwan Le Pennec (École polytechnique)

Arithmetic and Diophantine Geometry, via Ergodic Theory and o-minimality    A Conference in Honor of Emmanuel Ullmo’s 60th Birthday    September 8-12 2025 at IHES – Marilyn and James Simons Conference Center    How to get to IHES

This conference aims to honor the spectacular contributions of Emmanuel Ullmo to arithmetic geometry and centers around his mathematical contributions and interests. It will cover and highlight recent stage of development on topics such as Diophantine geometry, ergodic theory, Hodge theory, and arithmetic dynamics.
 Registration deadline: August 31, 2025
Speakers:

Fabrizio Andreatta (Univ. degli Studi di Milano)
Uri Bader (Weizmann Inst. & Univ. of Maryland)
Benjamin Bakker (Univ. of Illinois, Chicago)
Gregorio Baldi (CNRS, IMJ-PRG)
Yves Benoist (CNRS, Univ. Paris-Saclay)
Anna Cadoret (IMJ-PRG, Sorbonne Univ.)
François Charles (ENS Paris)
Laura DeMarco (Harvard Univ.)
David Fisher (Rice Univ.)
Javier Fresán (IMJ-PRG, Sorbonne Univ.)
Philipp Habegger (Univ. of Basel)
Philippe Michel (EPFL)
Hee Oh (Yale Univ.)
Naomi Sweeting (Princeton Univ.)
Yunqing Tang (Caltech & UC Berkeley)
David Urbanik (IHES)
Xinyi Yuan (BICMR, Peking Univ.)
Mingjia Zhang (IAS & Princeton Univ.)
Shouwu Zhang (Princeton Univ.)
Wei Zhang (MIT)

 
Organizing committee:     Ahmed Abbes (CNRS, IHES), Jennifer Balakrishnan (Boston Univ.), Ziyang Gao (UCLA), Marc Hindry (Univ. Paris-Cité), Fanny Kassel (CNRS, IHES), Bruno Klingler (Univ. Humboldt zu Berlin), Yuri Tschinkel (NYU and Simons Foundation)
 

Fuzzy Sphere Meets Conformal Bootstrap 2025

Since 2023, the fuzzy sphere regulator has become a valuable tool in analyzing 2+1D (quantum) phases transitions and comparing with CFT. After the first edition of the « Fuzzy Sphere Meets Conformal Bootstrap » workshop at the SCGP, Stony Brook (link to https://scgp.stonybrook.edu/archives/41863), this second meeting will bring together condensed matter and high energy physicists working on numerical methods, conformal field theory, and related areas.
For its second edition, the Fuzzy Sphere Meets Conformal Bootstrap workshop, organized by Emilie Huffman (Perimeter Institute), Slava Rychkov (IHES), Yin-Chen He (YITP, Stony Brook University), Liam Fitzpatrick (Boston University) will take place on June 2-6, 2025.
This workshop is supported by the Simons Collaboration on the Non-Perturbative Bootstrap
 

Running Seminar
 
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Séminaire de géométrie arithmétique
The classicality of the motivic Galois group is equivalent to the vanishing of all the higher degree operations on the cohomology of pairs of algebraic varieties. I will present a proof of this in a significant special case, namely the vanishing of degree-1 operations acting on the cohomology of smooth and projective varieties.
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Séminaire Amplitudes et Gravitation sur l’Yvette (IHES/IPhT)
Dual model amplitudes are meromorphic amplitudes involving the exchange of infinitely-many higher spin states. They are the staple of tree-level string theory, with the Veneziano and Virasoro-Shapiro amplitudes being their most famous representatives and also describe gauge theories in the large N limit. 
Amplitudes of this class must satisfy very constraining consistency conditions, which makes them good candidates for bootstrap approaches. Yet, only recently they are receiving the attention of the S-matrix bootstrap community, partly because many standard S-matrix bootstrap techniques are not well suited for their study.
In this talk I will show some recent progress in the analysis of dual model amplitudes from a bootstrap perspective using techniques from Regge theory of complex angular momentum. After a short motivation/introduction to dual model amplitudes and presenting the main ideas of Regge theory, I will explain how these techniques can be used to study them and showcase some recent results: the proof that dual model amplitudes require infinitely many trajectories to be consistent, and a numerical method to build consistent dual amplitudes with customizable spectrum and high energy behavior.
 
 
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Running Seminar
 
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Running Seminar
The main aim of the seminar is to construct a bridge between 3D Chern-Simons resurgence techniques on the quantum side and Galois representations, L-functions and Frobenius traces on the classical topology side.
 
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Séminaire Amplitudes et Gravitation sur l’Yvette (IHES/IPhT)
In gravity theories, the conservative tidal deformability of a self-gravitating object is parametrized in terms of a set of coefficients, commonly referred to as Love numbers. At leading order, these coefficients are obtained by solving the linearized static Einstein equations for the perturbations. In the talk, I will discuss the role of field nonlinearities in the calculation of the tidal deformability of compact objects. I will show that an infinite subset of nonlinear Love numbers of black holes is identically zero, a result that extends the well-known vanishing of linear Love numbers to higher orders in perturbation theory. Remarkably, this result follows from a fully nonlinear hidden symmetry structure in general relativity.
 
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In our study of positive representations with Jonas Beyrer, Beatrice Pozzetti, François Labourie, and Anna Wienhard, we introduced and investigated families of circles in flag manifolds that we called « photons ». This talk will present the basic properties of photons, as well as their relations with cross-ratios, and, if time permits, with collar lemmas for positive representations.