Mercredi 7 Janvier 2026, 13:30 à DPT-PHYS-ENS, ConfIV (E244) - 24 rue Lhomond 75005 PARIS	COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS)	physics
Amir Yacoby ( Université de Harvard )	Quantum Sensing of Quantum Matter
Abstract:	Important scientific discoveries often happen when scientists have new tools that let them look at complex physical problems in different ways. Recently, there have been exciting breakthroughs in the study of quantum materials. This has led scientists to create new methods for examining their basic qualities. In this talk, Yacoby will discuss some of the recent projects he's worked on to develop new local quantum sensing techniques. He will also talk about how these techniques can help us better understand quantum materials.

Jeudi 8 Janvier 2026, 10:00 à IHP, Amphi Darboux	RENC-THEO (Rencontres Théoriciennes)	hep-th
Romuald Janik ( Jagiellonian U. )	The Ising model as a window on quantum gravity with matter
Abstract:	In this talk, I show that the Ising model CFT can be used to obtain some surprising insights into 3D (quantum) gravity with matter. I review arguments for the existence of its holographic description, and analyze the time dependence of perturbations of the theory at high temperature, which would correspond to throwing matter into a black hole in the dual gravitational picture. After an initial exponential damping - consistent with absorption by the black hole - the signal remarkably reemerges intact again, apparently at odds with the expected conventional black hole behaviour. Using the exact solvability of the Ising model CFT, I provide an explanation of this phenomenon in terms of the properties of bulk matter fields interacting with the BTZ black hole. This is made possible by the fact that the geometry/metric is not fundamental but a derived quantity in the Chern-Simons formulation of 3D gravity, which allows for evading a variant of the black hole information paradox in the present context. I argue that the observed mechanism should be generic in the AdS3/CFT2 context and should apply for any CFT2. I also briefly mention some work in progress.

Jeudi 8 Janvier 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
Francesco Mori ( Harvard )	Dynamics and Control Out of Equilibrium: From Active to Learning Systems
Abstract:	Nonequilibrium systems are ubiquitous, from swarms of living organisms to machine learning algorithms. While much of statistical physics has focused on predicting emergent behavior from microscopic rules, a growing question is the inverse problem: how can we guide a nonequilibrium system toward a desired state? This challenge becomes particularly daunting in high-dimensional or complex systems, where classical control approaches often break down. In this talk, I will integrate methods from optimal control theory with techniques from statistical physics to tackle this problem in two broad classes of nonequilibrium systems: active matter—focusing on multimodal strategies in animal navigation and mechanical confinement of active fluids—and learning systems, where I will apply control theory to identify optimal learning principles for neural networks. Together, these approaches point toward a general framework for controlling nonequilibrium dynamics across systems and scales.

Jeudi 8 Janvier 2026, 11:00 à IJCLAB, 210/114	IJCLAB-PTH (Particle Theory Seminar of IJCLAB Orsay)	hep-th
Alessandro Podo ( IHES )	Naturalness of vanishing black-hole tides
Abstract:	I will present a symmetry argument for the vanishing and non-renormalization of static Love numbers for spherically symmetric black holes at nonlinear order, in D=4 classical General Relativity. The symmetry is realized both in full GR and in the worldline EFT, allowing for a unified treatment. This clarifies the naturalness of vanishing static Love numbers in the worldline EFT when including non-linearities, and extends previous vanishing results to all nonlinear static tides. When extended to higher dimensional gravity, this also explains the pattern of vanishing and running static Love numbers of electric and tensor type, and predicts new results at the nonlinear order. I will also apply the same arguments to the tidal response of shift-symmetric scalar fields, predicting new zeros and unifying them with the no-hair theorem for shift-symmetric scalar fields (and its violations). If time permits, I will also comment on the extension of these results to backgrounds with electro-magnetic and gravito-magnetic charges. Based on joint work with Julio Parra-Martinez.

Jeudi 8 Janvier 2026, 11:00 à IHES, Amphithéâtre Léon Motchane ( Séminaire de Géométrie Arithmétique )	MATH-IHES (TBA)	math
Konstantin Ardakov ( Mathematical Institute, University of Oxford )	On the mod-p Cohomology of Certain p-saturable Groups
Abstract:	The mod-$p$ cohomology of equi-$p$-saturable pro-$p$ groups has been calculated by Lazard in the 1960s. Motivated by recent considerations in the mod-$p$ Langlands program, we consider the problem of extending his results to the case of compact $p$-adic Lie groups $G$ that are $p$-saturable but not necessarily equi-$p$-saturable: when $F$ is a finite extension of $\mathbb{Q}_p$ and $p$ is sufficiently large, this class of groups includes the so-called pro-$p$ Iwahori subgroups of $SL_n(F)$. In general, using the work of Serre and Lazard one can write down a spectral sequence that relates the mod-$p$ cohomology of $G$ to the cohomology of its associated graded mod-$p$ Lie algebra $\mathfrak{g}$. We will discuss certain sufficient conditions on $p$ and $G$ that ensure that this spectral sequence collapses. When these conditions hold, it follows that the mod-$p$ cohomology of $G$ is isomorphic to the cohomology of the Lie algebra $\mathfrak{g}$.

Jeudi 8 Janvier 2026, 11:30 à IHP, Amphi Darboux	RENC-THEO (Rencontres Théoriciennes)	hep-th
Philine Van Vliet ( ENS )	TBA

Jeudi 8 Janvier 2026, 16:00 à LPENS, L378	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Francesca Mignacco ( Princeton )	Statistical physics of learning and collective computation in artificial and biological neural networks
Abstract:	Modern machine learning, powered by massive datasets and large-scale optimization, has achieved remarkable success across science and technology. Yet its progress remains largely empirical, lacking a unified theoretical framework that explains how and why these systems work. In parallel, experimental neuroscience now enables large-scale recordings of brain activity, offering the basis for quantitative theories that link microscopic neural interactions to macroscopic behavior. In this talk, I will use statistical physics as a unifying language to address these challenges through data-driven yet analytically tractable models. These models allow to identify key order parameters, i.e., interpretable summary statistics that capture collective neural computation. I will present applications of these methods to study the inductive biases of neural architectures, the structure of real datasets, and the learning curves of training algorithms viewed as controlled high-dimensional dynamical processes. Finally, I will outline future directions toward predictive theories that connect the dynamics of learning and the structure of neural representations to the emergence of flexible and robust computation in both brains and machines.

Vendredi 9 Janvier 2026, 12:00 à LPENS, L378	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Ananyo Maitra ( LPTM, CY Cergy Paris Université )	Tissues in their natural habitat: Using active matter hydrodynamics to understand the mechanics of cellular materials
Abstract:	Modelling cellular materials using nonequilibrium field theories—that are inspired by active matter hydrodynamics—has proved quite successful, yielding measurable qualitative predictions that have been verified in experiments. In this talk, I will illustrate different levels at which such modelling can be performed. The first level consists of hydrodynamic theory, which requires no specific input from any experiment; its predictions are universal and apply to any material, including tissues and cell layers, that belongs to that particular universality class. I will illustrate this with the example of a theory applicable to three-dimensional chiral tissues moving through the extracellular matrix. The second level consists of more experimentally motivated modelling that is not purely hydrodynamic in the sense that certain symmetry-mandated parameters are taken to be small, guided by observations. I illustrate this with the example of crawling skin cells that flock and travel as a solid. The third level consists of experimentally guided phenomenological continuum modelling. I will illustrate this with the example of cancer-associated fibroblasts that interact with their past orientations through fibronectin filaments they deposit on a surface.

Lundi 12 Janvier 2026, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-STA (Séminaire de Physique Statistique, CEA/Saclay)	physics
Sofia Flores	Vector Resonant Relaxation and Statistical Closure Theory. II. One-loop Closure
Abstract:	We use stellar dynamics as a testbed for statistical closure theory. We focus on the process of « Vector Resonant Relaxation, » a long-range, non-linear, and correlated relaxation mechanism that drives the reorientation of stellar orbital planes around a supermassive black hole. This process provides a natural setting to evaluate the predictive power of generic statistical closure schemes for dynamical correlation functions, in the fully non-linear and non-perturbative regime. We develop a numerical scheme that explicitly implements the seminal « Martin-Siggia-Rose » formalism at one-loop order via an iterative fixed-point approach, thereby improving upon the bare order from the « Direct Interaction Approximation. » Using this framework, we quantitatively validate the ability of the formalism to predict (i) the two-point two-time correlation function; (ii) the renormalised three-point interaction vertex; (iii) the three-point three-time correlation function. These predictions are compared to direct measurements from numerical simulations. We conclude by discussing the limitations of this approach and presenting possible future venues.

Lundi 12 Janvier 2026, 14:00 à IHES, Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets )	MATH-IHES (TBA)	math
Elise Goujard ( Université de Nantes )	Geometry of Large Genus Flat Surfaces
Abstract:	Gluing the opposite sides of a square gives a flat torus: a torus endowed with a flat metric induced by the Euclidean metric on the square. Similarly, one can produce higher genus surfaces by gluing parallel sides of several squares. These "square-tiled surfaces" inherit from the squares a flat metric with conical singularities. In this talk we will present several recent results and conjectures on the large genus asymptotics of these surfaces, and more generally of some families of flat surfaces (joint work with V. Delecroix, P. Zograf and A. Zorich). We will also see how these results can be interpreted in the language of closed curves on surfaces. I will finish by some recent results joint with E. Duryev and I. Yakovlev that should allow to generalize these results to a larger family of flat surfaces.

Lundi 12 Janvier 2026, 16:00 à IHES, Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets )	MATH-IHES (TBA)	math
Colin Davalo ( Università di Torino )	Slices of Representations of Surface Groups in $G_2$ and Associated Geometric Structures
Abstract:	In this talk we will consider two families of representations from the fundamental group of a closed surface of genus at least 2 into the exceptional Lie group G_2, and more precisely into its real split form G'_2. Representations in these families correspond to Higgs bundles of a very special form introduced by Collier and Toulisse. They come with associated equivariant objects: they admit an alternating almost-complex map into the pseudosphere S^2,4, which can be reinterpreted as a parallel distribution of planes along a minimal surface in the symmetric space. From the Higgs bundle description of these families, however, it is far from clear whether these representations have good geometric properties. In joint work with Parker Evans, we use the equivariant objects to construct explicitly a geometric structure associated to some of these representations. After an introduction to the geometry of G'_2 and to these two families of representations, I will present our results explaining how to construct for every representation \rho; in the first family a geometric structure modelled on a flag manifold of G2, the Einstein universe Ein^2,3, whose holonomy is \rho. This is a structure on a fiber bundle over the considered surface with fiber diffeomorphic to Ein^2,1.

Mardi 13 Janvier 2026, 11:00 à IPHT, Amphi Claude Bloch, Bât. 774	IPHT-GEN (Séminaire général du SPhT)
Matthew Headrick ( Brandeis University )	TBA
Abstract:	TBA

Mercredi 14 Janvier 2026, 11:00 à LPENS, L378	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Friedrich Huebner	TBA

Mercredi 14 Janvier 2026, 14:00 à CPHT, Salle de Conférence Louis Michel	SEM-CPHT (Séminaire du CPHT)	hep-th
Martin Pico ( Universidad Autonoma de Madrid )	Classifying consistent truncations from Exceptional Generalised Geometry
Abstract:	TBA

Jeudi 15 Janvier 2026, 11:00 à LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage	SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques)	hep-th|math.AG
Jean Doucot ( Institute of Mathematics of the Romanian Academy )	On the classification of moduli spaces of irregular connections on the Riemann sphere
Abstract:	The Riemann-Hilbert correspondence, providing an equivalence between connections on curves with regular singularities and monodromy representations, admits a vast generalization to the case of connections with irregular singularities, involving generalized monodromy data known as Stokes data. The Betti moduli spaces obtained in this way, the wild character varieties, now depend on the choice of a wild curve, including irregular classes encoding the form of the singularities. Remarkably, in genus zero, different wild curves (corresponding to connections with different ranks, number of singularities, and pole orders) can give rise to isomorphic moduli spaces. In the so-called simply-laced case, it was shown by Boalch that many such isomorphisms can be nicely encoded by the combinatorial datum of a supernova quiver. The wild character variety is then closely related to the corresponding Nakajima quiver variety. Moreover, a given supernova quiver can be read so as to obtain several wild curves with isomorphic wild character varieties. In this talk, I will describe how to generalize this combinatorial description of the symmetries of the simply-laced case to the case of irregular connections on the Riemann sphere with arbitrary singularity data; we obtain diagrams which generalize the supernova quivers, and are invariant under the Fourier transform. If time permits, I will also discuss some applications to physics, namely to dualities between Argyres-Douglas theories.

Jeudi 15 Janvier 2026, 14:00 à LPTMC, Jussieu, LPTMC seminar room, towers 13-12, 5th floor, room 523	SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)	cond-mat
Evgeny Stepanov ( CPhT )	TBA

Vendredi 16 Janvier 2026, 14:00 à LPTHE, Library ( In the library and via Zoom: https://cern.zoom.us/j/63031219326? pwd=STlDY2l0UTZOTWd3Ty8zaWVQSzNTdz09 )	LPTHE-PPH (Particle Physics at LPTHE)	hep-ph
Nicolas Grimbaum-Yamamoto ( ULB Bruxelles )	Primordial high energy neutrinos
Abstract:	In this talk, I will discuss the prospects for detecting high energy neutrinos produced before recombination by the decay or annihilation of early Universe relics. The focus is on identifying sharp spectral features, influenced by cosmological redshift and radiative effects, and determining when these features remain intact or are erased by interactions on the way to the detector. I will outline the viable ranges of particle mass, lifetime, and abundance consistent with cosmological and observational constraints, and identify which regions of parameter space remain promising for future searches. I will also briefly present our Monte Carlo treatment of spectral distortions of the primordial high energy neutrino spectrum induced by scattering on the cosmic neutrino background.

Lundi 19 Janvier 2026, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires)	physics
Sergei Nechaev ( LPTMS (Paris-Saclay) )	What do Lifshitz tails, KPZ, and BKT have in common?
Abstract:	Abstract:  (i) We study the statistics of stretched two-dimensional random walks (Brownian bridges) in the vicinity of an impermeable disc using the optimal?fluctuation approach. We show that the transverse span of the walks away from the boundary scales with the Kardar?Parisi?Zhang (KPZ) exponent $1/3$. (ii) Using the analogy between the optimal fluctuation in this setting and that in the one-dimensional Balagurov?Vaks trapping problem, we propose a connection between KPZ-like statistics and Lifshitz tails arising in a deterministic large-deviation landscape. (iii) By interpreting the radial component of the random walk above the disc as diffusion in a conformally invariant $1/r^{2}$ potential, we recover the Efimov?BKT behavior of the associated renormalization-group flow. From a large-deviation perspective, we argue that the typical paths responsible for the BKT-like behavior belong to a sub-ensemble of stretched Brownian bridges driven into the large-deviation regime.

Mardi 20 Janvier 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
Nils Caci ( LKB )	TBA

Mercredi 21 Janvier 2026, 11:00 à LKB, Charpak	SEM-LKB (Séminaire du Laboratoire Kastler Brossel)	quant-ph
Jonathan Pritchard ( University of Strathclyde )	Quantum computation and optimisation using neutral atom arrays
Abstract:	Neutral atoms have emerged as a powerful and scalable platform for quantum computing, offering the ability to generate large numbers of identical and high quality qubits in reconfigurable arrays. By coupling atom to highly excited Rydberg states with strong, long-range dipole-dipole interactions it is possible to perform high-fidelity two and multi-qubit gate operations, or to natively implement classical graph optimisation problems, highlighting the versatility for performing both analogue and digital quantum computing. In this talk we will present work at Strathclyde focused on developing large-scale system for quantum computing and optimisation, including demonstration of high fidelity single qubit gate operations on up to 225 qubits with errors below the threshold for fault tolerance using a non-destructive readout technique, as well as initial results from performing weighted graph optimisation using programmable local light-shifts across the atomy array. This provides a route to embedding a wider class of problems including quadratic unconstrained binary optimisation (QuBO) and integer factorisation, and extension to native implementations of graph colouring. Alongside progress towards large-scale analogue optimisation, we will present a new cryogenic dual-species setup targeting fault-tolerant digital computation using quantum error-correction. This approach offers suppression of mid-circuit readout errors due to use of atoms of different species, and will provide a versatile test-bed for prototyping and benchmarking performance and scalability of recently proposed quantum low-density parity check codes.

Jeudi 22 Janvier 2026, 14:00 à ESPCI, tba. ( Zoom link available at seminaires-lpem@espci.fr )	SEM-EXCEP (Seminaire exceptionnel)	cond-mat
Christoph Lange ( TU Dortmund University )	Frontiers in THz cavity QED: Deep-strong multi-mode coupling, subcycle nonlinearities, and diabatic switching
Abstract:	Dressing matter excitations with cavity photons can create novel, exotic quantum states. Ultrastrong coupling, where the ratio of vacuum Rabi frequency and carrier frequency of light, $\Omega_R/\omega_c$, approaches unity, has enabled vacuum-field modified transport, polaritonic chemistry, or strong mode squeezing and entanglement. Past investigations of this regime of cavity quantum electrodynamics (c-QED) focused on coupling of a single pair of light and matter modes, in equilibrium. Here, we discuss conceptually new extremes of c-QED. We demonstrate subcycle control of deep-strong coupling, where $\Omega_R/\omega_c$ is collapsed from 1.3 to zero within 5 $\%$ of the optical cycle duration, leading to characteristic trailing oscillations of the extinguished polariton states. Moreover, we investigate coherent subcycle nonlinearities of multiple cavity polaritons and observe dynamical mixing between otherwise orthogonal modes. Our most recent structures demonstrate extremely strong, multi-mode coupling of 20 matter resonances and multiple cavity modes over 6 optical octaves, boosting the number of virtual cavity photons beyond unity for the first time while achieving a record coupling strength of $\Omega_R/\omega_c$ = 3.19.

Vendredi 23 Janvier 2026, 12:00 à LPENS, L378	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Jéremie Guedj ( IAME, INSERM )	TBA

Mercredi 28 Janvier 2026, 11:00 à LPENS, L378	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Mikhail Feigel'man ( Nanocenter CENN and Jozef Stefan Institute, Ljubljana, Slovenia )	TBA
Abstract:	Disorder in quantum many-body systems can drive transitions between ergodic and non-ergodic phases, yet the nature of these transitions remains intensely debated. Using a two-dimensional array of superconducting qubits (their number n was up to 70), we study an interacting spin-1/2 model with XY coupling at high temperature in a strong random field along Z direction. Crucially, we were tracking dynamics both in real space and in Hilbert space. Over a broad disorder range, $10 < W < 35$, we observe an intermediate non-ergodic regime with glass-like characteristics: physical observables become broadly distributed and some - but not all - degrees of freedom are effectively frozen. The Hilbert-space return probability shows slow power-law decay, $R(t) \~ t^{-\eta}$ consistent with finite-temperature quantum glassiness. Exponent &#951; is found to show unusual dependence on the system size, $\eta(W) ~ &#954;(W) n^2$. In the same regime, we detect the onset of a finite Edwards-Anderson order parameter and the disappearance of spin diffusion. By contrast, at lower disorder, spin transport persists with a nonzero diffusion coefficient. Our experimental results are supplemented by semi-quantitative theory and by numerical simulations on smaller systems. In particular, we demonstrate the existence of an intermediate quantum state - with de-phasing but without relaxation - within a model of spins-1/2 residing at the Cayley tree. Thus we demonstrate the presence of non-ergodic glass-like state in two-dimensional quantum spin-1/2 system - that is not, however, fully localized in the sense of many-body-localization (MBL). The glassy phase we found is characterized by intrinsic spin de-phasing rate that is much larger than typical spin relaxation rate. At very strong disorder $W > 30$, the exponent $\eta(W)$ drops sharply towards zero for all studied system sizes, indicating plausible second transition into fully MBL state.

Mercredi 28 Janvier 2026, 13:30 à IHP, Amphi Choquet-Bruhat (batiment Perrin), Institut Henri Poincaré, Paris	SEED (Seed Seminar of Mathematics and Physics)	math-ph
Julio Parra-Martinez ( IHES )	TBA

Mercredi 28 Janvier 2026, 14:00 à CPHT, Salle de Conférence Louis Michel	SEM-CPHT (Séminaire du CPHT)	hep-th
André Pinheiro ( Heriot-Watt University )	Holographic fluids with higher-form symmetries
Abstract:	Higher-form symmetries are ubiquitous in physics. In this talk, I focus on the case where they are continuous and encode the conservation of extended objects. Applications include elasticity, superfluidity and phases of electromagnetism. Using holography, we explore effective descriptions of systems with the simplest case of a single higher-form symmetry. For energies well below temperature, these descriptions admit a (potentially extended) hydrodynamic regime. We verify this explicitly by studying AlAdS black branes charged under higher-form potentials. In particular, we compute quasinormal modes, starting with the low-density limit. Then, we focus on the bulk dual of a viscoelastic system and analyse instabilities for different equilibrium states corresponding to isotropic crystalline phases.

Mercredi 28 Janvier 2026, 14:00 à IJCLAB, 100/-1-A900 - Auditorium Joliot Curie (IJCLab) ( https://indico.ijclab.in2p3.fr/event/13160/ )	IJCLAB-HEP (Particle Physics Seminars at IJCLab)	hep-ph
Benjamin Fuks ( LPTHE, Sorbonne Université )	Toponium at the LHC: a new frontier in top-quark physics
Abstract:	The top quark, the heaviest known elementary particle, has long been thought unable to form bound states. However, intriguing hints in recent LHC data suggest that toponium, a short-lived quasi-bound state of a top-antitop pair, might have left observable traces in data and possibly even been discovered. In this talk, I will discuss why toponium is such a unique laboratory for studying the theory of the strong interaction in the non-relativistic regime, how modern techniques allow us to incorporate bound-state effects into state-of-the-art collider simulations, and what experimental signatures could reveal the presence of toponium in current and future LHC data. I will finally highlight recent results, ongoing searches and the exciting prospects for using toponium as a new window into the physics of the top quark.

Mercredi 28 Janvier 2026, 15:00 à IHES, Amphi Choquet-Bruhat (batiment Perrin)	SEED (Seed Seminar of Mathematics and Physics)	math-ph
Eric Pichon-Pharabod ( Max Planck Institute for Mathematics in the Sciences, Leipzig )	TBA

Mercredi 28 Janvier 2026, 16:30 à IHP, Amphi Choquet-Bruhat (batiment Perrin)	SEED (Seed Seminar of Mathematics and Physics)	math-ph
Roberta Angius ( University of Hamburg )	TBA

Jeudi 29 Janvier 2026, 14:00 à ESPCI, tba. ( Zoom link available at seminaires-lpem@espci.fr )	SEM-EXCEP (Seminaire exceptionnel)	cond-mat
Mikhail Feigel'man ( Univ. Grenoble Alpes, France and CENN Nanocenter, Slovenia )	Tba.
Abstract:	tba.

Vendredi 30 Janvier 2026, 12:00 à LPENS, L378	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Camille Gurantz ( IBPS )	TBA