Mardi 6 Octobre 2026, 14:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires)	physics
Patrick Mcblain	Microcausality Bounds on Goldstone Dispersion Relations
Abstract:	Abstract: Lorentz invariance is the cornerstone of modern physics. However, many ?real-world? systems from condensed matter to cosmology have a preferred background which spontaneously breaks Lorentz invariance, consequently yielding Goldstone bosons. In this talk, we will show that the notion of microcausality survives the symmetry breaking, implying analyticity of the retarded two-point function. Using that, we show that dispersion relations of non-dissipative Goldstone modes can be written in terms of ?typically-real functions?, yielding two-sided bounds on Wilson coefficients of higher-derivative operators as explicit functions of the sound speed. We check these bounds against multiple systems such as the U(1) superfluid and QED. Finally, we will comment on the implications for cosmology through the EFT of Inflation.

Mardi 6 Octobre 2026, 14:45 à IHES, Amphithéâtre Léon Motchane	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Bernardo Zan ( Università di Genova )	On the Wilson-Fisher Fixed Point in the Limit of Integer Spacetime Dimensions
Abstract:	The Wilson–Fisher (WF) fixed point, a scalar field theory with a quartic interaction in d = 4 - \epsilon dimensions, is the textbook example of a weakly coupled CFT. The epsilon expansion accurately reproduces the critical exponents of the d = 3 and the d = 2 Ising model. This has led to the common view that WF defines a continuous family of CFTs in non-integer dimensions, interpolating between the free theory at d=4 and the Ising model at d = 3 and d = 2. In this talk I will look at what happens to the WF CFT when the number of dimensions approaches an integer value. Identifying the d->2 limit of WF as the 2d Ising CFT raises some issues, related to the fact that the d=2 CFT has infinitely many conserved currents that the d>2 theory does not have. I will propose a scenario, inspired by some exactly solved two-dimensional models, where the d->2 limit of WF contains the d=2 Ising CFT as a subsector, but contains more operators which do not completely decouple from the Ising subsector. I will explain why this makes the task of obtaining a d= 2 + \epsilon expansion for the Ising model harder.

Mercredi 7 Octobre 2026, 15:15 à IHES, Amphithéâtre Léon Motchane ( Séminaire Amplitudes et Gravitation sur l’Yvette (IHES/IPhT) )	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Chia-Hsien Shen ( National Taiwan University, Taipei )	Gravitational Sommerfeld Effects: Framework and Applications
Abstract:	Sommerfeld effects describe long-distance corrections to radiation emitted by a short-distance source. They play an important role in atomic physics and dark matter phenomenology, but the same mechanism also arises in gravitational-wave radiation from compact binaries. In this talk, I will develop a systematic framework for gravitational Sommerfeld effects by combining worldline effective field theory with black hole perturbation theory. A key advantage of this framework is that it organizes high-order perturbative calculations without requiring any nontrivial loop integration, allowing us to compute the waveform to tenth order in the perturbative expansion and beyond. The formulation also reveals an exact connection between the radiation waveform and Compton scattering, as well as the underlying structures of the classical renormalization group of the multipoles and tidal Love numbers. I will conclude by discussing how these results can be incorporated into waveform resummation models for gravitational-wave signals. This talk is based on arXiv:2604.14112 with Chih-Hao Chang and Zihan Zhou, and work in progress.

Jeudi 8 Octobre 2026, 11:00 à IHES, Amphithéâtre Léon Motchane	MATH-IHES (TBA)	math
Yoichi Mieda ( The University of Tokyo )	On “Siegel Domains” in p-adic Period Spaces
Abstract:	A Siegel domain is a finite-volume subset of a symmetric space whose translates under the action of the relevant arithmetic group cover the entire space. In this talk, we consider an analogue for the p-adic period spaces introduced by Rapoport and Zink. We give a partial criterion for the existence of a Siegel domain and discuss its expected applications.

Jeudi 8 Octobre 2026, 11:00 à LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage	SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques)	hep-th
Veronica Fantini ( Laboratoire de Mathématiques d'Orsay )	Modular Resurgence
Abstract:	Many physical observables are usually divergent asymptotic expansions, and their divergence is informative. The factorial growth of the coefficients hides non- perturbative, exponentially small corrections, which can be reconstructed by applying Ecalle's theory of resurgence. Sometimes, these observables are also expected to be invariant under the action of a subgroup $\Gamma\subseteq\{\rm SL}_2(\mathbb{Z})$ only up to a holomorphic correction: classical modularity fails, but it does so in a controlled way. Zagier’s notion of a (holomorphic) quantum modular form formalises this controlled failure as a cocycle condition with better analytic properties. In this talk, I will present the framework of modular resurgence, which identifies a class of quantum modular forms by characterizing the resurgent structure of their asymptotics. This has been applied to describe a strong-weak symmetry in topological strings on local Calabi-Yau 3- folds, and to detect the modular structure of certain observables.

Jeudi 8 Octobre 2026, 14:00 à LPENS, Conf IV	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Mathis Gueneau	Large Deviations in Switching Diffusion: Trajectory Condensation and Diffusivity BBP Transition
Abstract:	We consider a Brownian particle whose diffusivity changes at Poissonian switching times, with each new value drawn independently from a bounded distribution W(D). Assuming that W(D) \sim C(D_{\max}- D)^\nu near its upper edge, we study rare ballistic displacements x(t)= yt, far beyond the typical diffusive scale. Our previous work [1] obtained the corresponding large-deviation rate function and revealed a rich structure of dynamical transitions depending on the value of \nu. Here, we ask a complementary question: what do the trajectories realizing these rare displacements actually look like? We characterize the distribution of the displacement accumulated during a single interval between two switches, conditioned on the endpoint x(t)=yt. We show that the transitions in the rate function correspond to a dynamical condensation phenomenon. For moderate displacements, the total displacement is shared among O(t) microscopic increments. Beyond a critical regime, however, a single interval produces a macroscopic O(t) increment carrying a finite fraction of the total displacement. A complementary picture emerges in the moment-generating function. There, the transition corresponds to a change from collective contributions of many diffusivity states to the selection of diffusivities close to D_{\max}. By reformulating the tilted dynamics as a rank-one random matrix problem, we identify this transition with a BBP-type spectral transition. Thus, the diffusivity BBP-type selection and trajectory condensation at fixed displacement provide two complementary descriptions of the same underlying mechanism. Finally, we test the predicted condensate structure using rare-event sampling and find excellent agreement with the analytical results. [1] M. Guéneau, S. N. Majumdar, and G. Schehr, Phys. Rev. Lett. 135, 067102 (2025) [2] M. Guéneau, T. Shorlepp, S. N. Majumdar, and G. Schehr, in preparation (2026)

Jeudi 8 Octobre 2026, 14:00 à LPENS, LPENS Library - E239	LPENS-PH (LPENS Particle physics phenomenology and cosmology)	hep-th
Elias Furrer ( Rutgers U. )	Topological SQCD, Segre Numbers and Mass Singularities
Abstract:	Topologically twisted supersymmetric gauge theories provide a bridge between four- manifold topology, Seiberg–Witten geometry and intersection theory on moduli spaces. I will discuss four-dimensional N=2 supersymmetric QCD with massive fundamental hypermultiplets on a compact four-manifold. Supersymmetric localisation reduces the path integral to the moduli space of non-Abelian monopoles, and equivariant localisation further separates it into contributions from the instanton and monopole branches. This ultraviolet description can be compared with an infrared computation based on the Seiberg–Witten solution. In the limit of large equal masses, the instanton contribution admits an expansion governed by virtual Segre numbers of moduli spaces of higher-rank sheaves, allowing us to extract their generating functions directly from the Seiberg–Witten curve. We find precise agreement with results of Göttsche and Kool for gauge groups SU(2) and SU(3), and I will discuss the generalisation to SU(N) QCD. For generic masses, combining the instanton and monopole branches produces symmetric root sums and hence rational functions of the masses. I will present a universal formula for these functions and their singularities at colliding masses. For the superconformal SU(2) theory with four flavours, partition functions are triality-invariant modular forms, in agreement with S-duality. Based on joint work with J. Manschot, G. Moore and R.K. Singh.

Vendredi 9 Octobre 2026, 10:00 à IPHT, Salle Claude Itzykson, Bât. 774	COURS (Cours)	physics
Grégoire Misguich	Matrix-product states and tensor networks: a gentle introduction 2/3
Abstract:	Abstract:  These lectures will provide an introduction to tensor-network methods in quantum many-body physics, with an emphasis on matrix-product states (MPS). Basic tensor-network language, including graphical notation, virtual indices, bond dimensions, gauge freedom, canonical forms, QR and singular-value decompositions, and the role of entanglement in controlling the efficiency of the representation. Main MPS algorithms, including contractions, correlation functions, matrix-product operators, DMRG, and time-evolution methods. Brief introduction to projected entangled-pair states (PEPS) as a higher-dimensional generalization of MPS, together with the basic ideas behind approximate PEPS contraction. Tensor-network representations of mixed states, quantum channels, and Lindblad dynamics, with applications to thermal states and open quantum systems. Based on https://arxiv.org/abs/2606.24803. Website: courses.ipht.frLivestream: youtube.com/IPhT-TV (free access)Videoconference (non-IPhT attendees): to receive the links join the course newsletter, see courses.ipht.fr/subscriptions

Vendredi 9 Octobre 2026, 13:00 à LPENS, Salle Camille Marbo, 29 ULM	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Maria Martinez Rodriguez ( Yale University )	Machine learning-driven modeling of B and T cells receptors
Abstract:	Deep learning has transformed protein science, enabling increasingly accurate structure prediction, protein language modeling, and generative protein design. Yet immune receptors remain a particularly difficult frontier: for antibodies and T cell receptors, accurate global folds are not sufficient. Binding specificity, cross-reactivity, and affinity are governed by flexible interfaces where current structure prediction models often have the lowest confidence. In this talk, I will discuss our work developing machine learning approaches to model B and T cell receptor recognition. I will first introduce how molecular dynamics-informed generative models can capture TCR conformational ensembles beyond static structures, with implications for predicting peptide recognition and cross-reactivity. I will then describe graph-based models of antibody–antigen affinity that integrate structural representations with protein language model embeddings to improve generalization across antibody families and antigens. Finally, I will present ongoing work on TCR–peptide binding prediction, de novo design of pMHC binders, and fine-tuning protein language models to improve zero- shot ranking of immune receptor–ligand interactions. Together, these examples illustrate a central theme: the next generation of immune receptor modeling will require moving beyond static structure prediction toward models that integrate sequence, structure, dynamics, and biophysical constraints at the binding interface.

Vendredi 9 Octobre 2026, 14:00 à LPTMC, campus Jussieu, couloir 12-13, 5ème étage, salle 5-23	SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)	cond-mat
Alberto Dinelli ( Genève )	Motility regulation in active (eco)systems
Abstract:	Active matter describes systems whose constituents generate non-conservative forces on their environment, leading to the wealth of emergent phenomena encountered in the living world. In particular, the regulation of motility at the particle scale, either via external cues or quorum-sensing interactions with peers, can dramatically affect the self-organization of active systems. In the first part of my talk, I will show how one can bridge the gap between particle-based dynamics and hydrodynamic descriptions of motility-regulated active systems, by deriving generalized Green-Kubo relations for a broad class of motility-regulated active systems. [1,2] Building on these results, I will investigate the role of random motility regulation in the self-organization of microbial ecosystems consisting of N > > 1 species. Combining particle-based simulations with random matrix theory, I will show how weak, random interactions are sufficient to fragment the ecosystem into distinct, spatially segregated communities. Our results hold for a variety of motility-regulation mechanisms, and highlight the need to characterize the role of motility regulation in experimentally relevant situations. [3] [1] AD, P. L. Muzzeddu, arXiv 2604.09447 (2026) [2] AD, P. L. Muzzeddu, arXiv 2604.09453 (2026) [3] AD, A. Altieri, J. Tailleur, Phys. Rev. E 114, 014404 (2026)

Vendredi 9 Octobre 2026, 14:00 à LPTHE, LPTHE Library, 13-14.401	LPTHE-PPH (Particle Physics at LPTHE)	hep-ph
Tracy Slatyer ( MIT )	How to Unitarize the Sommerfeld Enhancement

Lundi 12 Octobre 2026, 11:00 à IPHT, Salle Claude Itzykson	IPHT-PHM (Séminaire de physique mathématique)	hep-th
Francesco Mangialardi ( DESY Hambourg )	Integrability of d-dimensional conformal blocks on non-trivial geometries
Abstract:	I will discuss conformal field theory on a vast class of d-dimensional manifolds, built by gluing cylinders and spheres. These manifolds carry a notion of genus, with genus zero corresponding to the sphere, and genus one to finite temperature CFT.  I will explain how conformal blocks on these manifolds are related to quantum Hitchin integrable systems, and to the Wess-Zumino-Novikov-Witten models of 2d CFT. In particular, I will use the integrable Hamiltonians for deriving differential equations for d-dimensional conformal blocks.  These ideas generalize the relation between sphere conformal blocks and Gaudin integrable models, and embed d-dimensional conformal blocks in 2d CFTs and supersymmetric gauge theories. Based on joint work with Ilija Buri?, Francesco Russo and Volker Schomerus (to appear)

Mardi 13 Octobre 2026, 10:45 à LPTMC, campus Jussieu, couloir 12-13, 5ème étage, salle 5-23	SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)	cond-mat
Léo Touzo ( U. Chicago )	TBA

Mardi 13 Octobre 2026, 14:00 à LPTHE, library	LPTHE-PPH (Particle Physics at LPTHE)	hep-ph
Simone Devoto ( Gent University )	TBA

Mercredi 14 Octobre 2026, 01:30 à DPT-PHYS-ENS, ConfIV - 24 rue Lhomond 75005 PARIS	COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS)	physics
Zaki Leghtas ( LPENS, Mines Paris )	Superconducting circuits: from fundamental science to quantum technologies
Abstract:	The 2025 Nobel Prize in Physics was awarded to John Clarke, Michel Devoret and John Martinis for showing that a superconducting electrical circuit - a macroscopic object made of wires and plates, with currents flowing and voltage drops - can behave quantum mechanically. In this colloquium, I will revisit these foundational experiments and follow what grew out of them. Thanks to superconductivity that eliminates dissipation and the Josephson effect that introduces nonlinearity, these circuits have been turned into quantum bits (qubits). Their coherence times have improved by six orders of magnitude over twenty-five years, and tech giants such as Google and IBM manufacture chips with hundreds of superconducting qubits, planning to scale towards a universal quantum computer. Finally, I will present the research of the QUANTIC team, where we design new qubits, both to improve quantum coherence and build ultra-sensitive detectors.

Mercredi 14 Octobre 2026, 11:00 à IHES, Amphithéâtre Léon Motchane	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Balt Van Rees ( Ecole polytechnique )	The doubly conformal dispersion relation
Abstract:	We provide a simple derivation of the conformal dispersion relation of Carmi and Caron-Huot which reconstructs a CFT four-point function from its double discontinuity. We exhibit a hidden conformal symmetry which explains the appearance of the "magic variable" x as a simple cross-ratio, built from four physical cross-ratios. We also introduce a regulator in the double discontinuity operation and then prove that one subtraction suffices for all integrals to converge.

Jeudi 15 Octobre 2026, 10:00 à IHP, Choquet Bruhat	RENC-THEO (Rencontres Théoriciennes)	hep-th
Tba	TBA

Vendredi 16 Octobre 2026, 10:00 à IPHT, Salle Claude Itzykson, Bât. 774	COURS (Cours)	physics
Grégoire Misguich	Matrix-product states and tensor networks: a gentle introduction 3/3
Abstract:	Abstract:  These lectures will provide an introduction to tensor-network methods in quantum many-body physics, with an emphasis on matrix-product states (MPS). Basic tensor-network language, including graphical notation, virtual indices, bond dimensions, gauge freedom, canonical forms, QR and singular-value decompositions, and the role of entanglement in controlling the efficiency of the representation. Main MPS algorithms, including contractions, correlation functions, matrix-product operators, DMRG, and time-evolution methods. Brief introduction to projected entangled-pair states (PEPS) as a higher-dimensional generalization of MPS, together with the basic ideas behind approximate PEPS contraction. Tensor-network representations of mixed states, quantum channels, and Lindblad dynamics, with applications to thermal states and open quantum systems. Based on https://arxiv.org/abs/2606.24803. Website: courses.ipht.frLivestream: youtube.com/IPhT-TV (free access)Videoconference (non-IPhT attendees): to receive the links join the course newsletter, see courses.ipht.fr/subscriptions

Lundi 19 Octobre 2026, 14:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Yin-Chen He ( Perimeter Institute & IHES )	Fuzzy Sphere Meets CFT: 3D Ising, Fermions and Gauge Theories (1/4)
Abstract:	In this series of lectures, I will introduce the "fuzzy (non-commutative) sphere regularization," a recently proposed non-perturbative approach to 3D CFTs. I will first elucidate its fundamental concepts and then dive into illustrative examples, including the 3D Ising transition, fermionic CFTs, and Chern-Simons matter theories. I will comment on the potential theoretical direction in understanding fuzzy sphere regularization from the aspect of algebra on fuzzy sphere.

Mardi 20 Octobre 2026, 14:00 à LPTHE, library	LPTHE-PPH (Particle Physics at LPTHE)	hep-ph
Arunima Bhattacharya ( Valencia University )	TBA

Mercredi 21 Octobre 2026, 13:00 à IHP, Amphithéâtre Yvonne Choquet-Bruhat ( Registration: https://indico.math.cnrs.fr/event/17376/ )	SEED (Seed Seminar of Mathematics and Physics)	math|physics
Seed Seminar	AI and the future of mathematics and physics (13:00-18:00)
Abstract:	Kick-off event with six short perspective talks followed by a round-table discussion. Speakers: Simon Machado, Miranda Cheng, François Charton, Antoine Chambert-Loir, Antoine Tilloy, Baptiste Cerclé

Jeudi 22 Octobre 2026, 11:00 à IHES, Amphithéâtre Léon Motchane ( Séminaire de Géométrie Arithmétique )	MATH-IHES (TBA)	math
Robin Zhang ( IHES )	Finiteness and Density Problems for (Positive) Integral Points on Mordell–Schinzel Surfaces
Abstract:	In 1952, Mordell erroneously claimed that the surface xyz = G(x,y) has infinitely many integral points for any G ∈ ℤ[x,y]. I will discuss a classification for finiteness and Zariski density of (positive) integral points on these log K3 surfaces when the coefficients of G are non-negative. This combines a dynamical argument proposed by Mordell, the theory of generalized cluster algebras, and the Killing–Cartan classification of semisimple Lie algebras. This talk is partially based on joint work with Antoine de Saint Germain.

Jeudi 22 Octobre 2026, 14:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Yin-Chen He ( Perimeter Institute & IHES )	Fuzzy Sphere Meets CFT: 3D Ising, Fermions and Gauge Theories (2/4)
Abstract:	In this series of lectures, I will introduce the "fuzzy (non-commutative) sphere regularization," a recently proposed non-perturbative approach to 3D CFTs. I will first elucidate its fundamental concepts and then dive into illustrative examples, including the 3D Ising transition, fermionic CFTs, and Chern-Simons matter theories. I will comment on the potential theoretical direction in understanding fuzzy sphere regularization from the aspect of algebra on fuzzy sphere.

Lundi 26 Octobre 2026, 14:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Yin-Chen He ( Perimeter Institute & IHES )	Fuzzy Sphere Meets CFT: 3D Ising, Fermions and Gauge Theories (3/4)
Abstract:	In this series of lectures, I will introduce the "fuzzy (non-commutative) sphere regularization," a recently proposed non-perturbative approach to 3D CFTs. I will first elucidate its fundamental concepts and then dive into illustrative examples, including the 3D Ising transition, fermionic CFTs, and Chern-Simons matter theories. I will comment on the potential theoretical direction in understanding fuzzy sphere regularization from the aspect of algebra on fuzzy sphere.

Mercredi 28 Octobre 2026, 14:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Yin-Chen He ( Perimeter Institute & IHES )	Fuzzy Sphere Meets CFT: 3D Ising, Fermions and Gauge Theories (4/4)
Abstract:	In this series of lectures, I will introduce the "fuzzy (non-commutative) sphere regularization," a recently proposed non-perturbative approach to 3D CFTs. I will first elucidate its fundamental concepts and then dive into illustrative examples, including the 3D Ising transition, fermionic CFTs, and Chern-Simons matter theories. I will comment on the potential theoretical direction in understanding fuzzy sphere regularization from the aspect of algebra on fuzzy sphere.

Mercredi 4 Novembre 2026, 10:30 à IHES, Amphithéâtre Léon Motchane	SEED (Seed Seminar of Mathematics and Physics)	math-ph
Tba	TBA

Mercredi 4 Novembre 2026, 11:45 à IHES, Amphithéâtre Léon Motchane	SEED (Seed Seminar of Mathematics and Physics)	math
Thomas Mordant ( LMO )	TBA

Jeudi 5 Novembre 2026, 10:00 à IHP, Choquet Bruhat	RENC-THEO (Rencontres Théoriciennes)	hep-th
Tba	TBA

Jeudi 12 Novembre 2026, 11:00 à LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage	SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques)	hep-th
Piet Lammers ( Sorbonne )	TBA

Vendredi 13 Novembre 2026, 13:00 à LPENS, Conf IV	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Min Wu ( Worcester Polytechnic Institute )	TBA