Mardi 26 Mai 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
Mathis Guéneau ( Max Planck Dresden )	Spatiotemporal Characterization of Active Dynamics in Channels: Theory and Experiments
Abstract:	Swimming microorganisms often live in confined, complex environments, where they transition between bulk and near-surface dynamics. Their dynamics can be quantified in terms of first-passage statistics. In this talk, I will first consider run-and-tumble bacteria confined in a channel. Combining theoretical predictions based on a renewal framework with experimental observations of Escherichia coli, we study the statistics of the time required, after leaving one wall, to encounter either wall. I will discuss how incorporating heterogeneity in tumbling rates or non-exponential run-duration distributions affects the survival probability. In the second part of the talk, I will consider active Brownian dynamics between two walls. Using a systematic expansion, we compute first-passage properties. Exploiting Siegmund duality, we infer the corresponding spatial properties for active Brownian particles confined between hard walls and reveal a transition towards a wall-accumulated state, reminiscent of experimental observations.

Mardi 26 Mai 2026, 11:00 à LPENS, 29 Rue d'Ulm, salle Marbo ( Balades Quantiques. Attention: unusual day! )	SEM-EXCEP (Seminaire exceptionnel)	cond-mat.stat-mech
Pok Man Tam ( Princeton University )	Quantum Shape of Matter
Abstract:	Geometry has shaped our understanding of the physical world since antiquity. In today’s quantum era, advances in experimental probes are revealing a new notion of “shape” encoded in the wavefunctions of quantum matter. In this talk, I will show how topology and geometry provide powerful frameworks for characterizing quantum materials and give rise to experimentally accessible signatures. First, I will discuss the topology of metallic systems, where global properties of the Fermi sea define distinct phases, and present recent developments demonstrating how quantized correlation and transport effects can probe this topology in both solid-state and ultracold-atom platforms. I will then discuss the notion of quantum geometry, which describes the local structure of electronic wavefunctions, and show how charge fluctuations provide a versatile probe of the quantum metric in both insulators and metals. Together, these results illustrate how the “quantum shape” of matter can be directly accessed in experiments and connected to the information content of many-body systems, opening new avenues for understanding and engineering quantum materials.

Mardi 26 Mai 2026, 11:30 à LPTHE, LPTHE library	SEM-LPTHE (Séminaire du LPTHE)	hep-th
Claudia Rella ( IHES )	TBA

Mardi 26 Mai 2026, 14:00 à LPENS, LPENS Library - E239	LPENS-PH (LPENS Particle physics phenomenology and cosmology)	hep-th
Alexander Migdal ( IAS )	Geometric QCD II: The Confining Twistor String and Meson Spectrum
Abstract:	We present the exact analytic solution of the Makeenko-Migdal loop equations, solving planar QCD (Nc→∞) in the continuum limit. Quantizing internal Majorana fermions (elves) on a rigid Hodge-dual minimal surface provides the algebraic mechanism satisfying the unintegrated vector loop equations. The Pauli principle exactly cancels non-planar intersections to reproduce planar factorization, while iterating the equation generates the planar graphs of asymptotically free QCD. Holographically fixing the bulk geometry by the boundary loop strictly avoids Liouville instability. Momentum loop space integrates out coordinate-space cusp singularities, yielding a finite local limit. Gauge-fixing the Virasoro constraint parametrizes the reduced phase-space measure by boundary twistors. The theory reduces to a confining analytic twistor string: a boundary sigma model S1→(S3×S3)/S1 coupled to a holographically determined Liouville field. The meson spectrum becomes a 1D functional integral over boundary twistor trajectories. Complexified action monodromies reveal a discrete mass spectrum governed by Catastrophe Theory, classified by the topological number of twistor poles inside the unit circle. This geometric localization is an infinite- dimensional realization of Exact WKB analysis and Picard-Lefschetz resurgence, where twistor poles act identically to Seiberg-Witten branch points. The 1-pole sector yields the exact Regge spectrum m2=πσ2(n+1/24), matching experimental π,K,ρ trajectories within 95% confidence. The empirically correct open-string intercepts emerge directly from the conformal anomaly of the microscopic elves rather than macroscopic string vibrations. Ultimately, this explicitly realizes Witten's Master Field as a critical classical trajectory in twistor space.

Mardi 26 Mai 2026, 14:00 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Kenji Nakanishi ( RIMS, Kyoto University & IHES )	Classification of Initial Data for Global Dynamics of Nonlinear Dispersive Equations (1/4)
Abstract:	Nonlinear dispersive equations are partial differential equations to describe various wave phenomena where the primary effects are wave dispersion and nonlinear interactions. Even a single equation can have many different types of solutions depending on the initial data, such as scattering, blow-up, and solitons. The theme of this course is to classify global behavior of solutions in terms of the initial data. More precisely, the problem is to characterize the set of initial data corresponding to each type of solutions, together with the configuration of those sets, which also requires to analyze transient evolutions during intermediate time. Despite the recent progress for the soliton resolution conjecture, which classifies the asymptotic behavior, its link to the initial data is much less understood, mostly restricted in the data size, types of behavior, and by symmetry of the equation or the solutions. The lecture will focus on two model cases as attempts to extend it in two directions. The first is to extend the initial data set to more variety of solutions; we consider the nonlinear Klein-Gordon equation and initial data near superposition of the ground state solitons, which are unstable. It is natural to expect that the classification is also a superposition of the single soliton case, but the interactions among unstable modes of different growth rates and large radiation from collapsed solitons can possibly spoil such a simple picture, by energy transfer from the most unstable mode to the others. I will show how to preclude it by using elementary geometry of the Lorentz transform and space-time weighted energy tailored for radiations from multi-solitons. The second is to extend the equations to less symmetry; we consider the Zakharov system, which is a system of the Schrodinger and the wave equations with Hamiltonian and mass conservation, but without the Galilei or Lorentz invariance, nor the center of mass or energy. Such loss of structure poses serious difficulty especially in proving the rigidity that the minimal non-dispersive solutions must be the ground states. I will show how to overcome it, by combining virial-variational estimates and space-time estimates for non-radiative source terms.

Mardi 26 Mai 2026, 14:45 à IHES, Centre de conférences Marilyn et James Simons	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Jesse Thaler ( MIT/IAIFI/IHES/IPhT )	Descending into the Modular Bootstrap
Abstract:	The modular bootstrap has been a powerful tool for carving out the landscape of allowed two-dimensional conformal field theories (CFTs). In this talk, I describe a complementary approach to standard modular bootstrap bounds: using modern machine learning strategies to actively search for CFT spectra that yield a valid torus partition function. Using insights from statistical inference and a custom singular-value-based optimizer, I present evidence for an obstruction to finding CFTs with small central charge and large spectral gaps, and I speculate on what this might imply for the structure of the CFT landscape. Along the way, I reflect on "centaur" approaches to theoretical physics, where human physicists and artificial intelligence collaborate to explore spaces of theories that would be difficult to navigate alone.

Mercredi 27 Mai 2026, 10:30 à IHES, Amphithéâtre Léon Motchane	SEED (Seed Seminar of Mathematics and Physics)	math-ph
Maddalena Ferragatta ( CPhT, École polytechnique )	TBA

Mercredi 27 Mai 2026, 11:30 à IPA, Institut Pascal	WORK-CONF (Workshop or Conference)	cond-mat.str-el|cond-mat.supr-con
Davide Valentinis ( Karlsruhe Institute of Technology )	Disordered electronic interactions as a route to non-Fermi liquids and quantum critical superconductivity in strange metals
Abstract:	Strange metals and bad metals constitute exotic but ubiquitous metallic phases, endowed with anomalous thermodynamic and spectroscopic properties, that do not comply with the conventional Landau Fermi-liquid (FL) paradigm [1,2]. Functional materials such as heavy fermions, pnictides, and high-temperature superconducting cuprates all host strange/bad metallic states of strongly interacting electrons; specifically, these states occur in the crossover region between distinct stable phases, as a function of a non-thermal tuning parameter like chemical doping or pressure. Such tunability suggests the presence of quantum critical points (QCPs) or extended quantum critical phases, i.e., zero-temperature phase transitions in the phase diagram, which engender non-Fermi liquid (NFL) physics at finite temperature through strong fluctuations of an associated soft bosonic mode (e.g., charge/spin density, nematic, or magnetic fluctuations)[1]. These soft modes are characterized by a proper frequency that decreases with decreasing distance from the QCP, and eventually vanishes at the quantum phase transition. Within this context, the two-dimensional (2D) spatially disordered Yukawa-Sachdev-Ye-Kitaev (YSYK) theory provides an exactly solvable platform to analyze non-Fermi liquid states and their associated phenomenology, microscopically rooted in quantum criticality [3-8]. Specifically, this model entails 2D dispersive fermions and bosons, coupled through interactions that are random in all internal degrees of freedom (“flavours”), and are spatially disordered (contact-like). The theory becomes exactly solvable in the limit of large number of flavours, and after averaging over disordered interactions, yielding self-consistent saddle-point (mean-field) equations analogous to an Eliashberg problem for strong-coupling superconductivity. As shown in an ongoing series of works, the 2D-YSYK model qualitatively reproduces several unconventional properties of strange metals: a linear-in-temperature (-linear) DC resistivity [9-12], which crosses over into the bad-metal regime when the resistivity becomes larger than the 2D quantum unit ; universal scalings of the optical conductivity as a function of frequency [13], due to a marginal Fermi liquid (MFL) ground state; superconductivity below a critical temperature , maximal when the system is tuned to quantum criticality; a finite superfluid phase stiffness and associated coherence peaks in the superconducting spectral functions, born out of incoherent, NFL normal-state spectra [14-16]. The most recent addition to this survey considers the evolution of normal-state transport in the presence of an applied magnetic field . By exactly solving the interacting Landau-level problem for our 2D-YSYK model with quadratic fermionic dispersion, we find an effective cyclotron resonance frequency in the conductivity that shifts linearly with applied magnetic field and is renormalized by disordered interactions [7], analogously to recent magnetoconductivity experiments on cuprates [17]. In addition, we present exact numerical results for the DC magnetoconductivity tensor on a square lattice, at first order in applied perpendicular magnetic field [8]. We calculate the longitudinal and Hall conductivities, the Hall coefficient, the carrier mobility, and the cotangent of the Hall angle, at fixed fermion density. From the interplay between YSYK interactions and square-lattice embedding, and the non-Boltzmann frequency-dependent self-energies, we find a superlinear evolution of the Hall-angle cotangent and the inverse carrier mobility with temperature, concomitant with linear-in-temperature resistivity, in an extended crossover regime above the low-temperature MFL ground state. These findings qualitatively agree with the superlinear (-like) behaviour of the Hall angle cotangent [18-20] in cuprates. References 1. D. Chowdhury et al., Rev. Mod Phys. 94, 035004 (2022) 2. G. R. Stewart, Rev. Mod. Phys. 73, 797 (2001) 3. I. Esterlis et al., Phys. Rev. B 103, 235129 (2021) 4. H. Guo et al., Phys. Rev. B 106, 115151 (2022) 5. A. A. Patel et al., Science 381, 790 (2023) 6. C. Li et al., Phys. Rev. Lett. 133, 186502 (2024) 7. H. Guo et al., Phys. Rev. B 109, 075162 (2024) 8. D. Valentinis et al., arXiv:2511.01030 (2025) (accepted for publication in Phys. Rev. Research) 9. S. Kasahara et al., Phys. Rev. B 81, 184519 (2010) 10. P. Giraldo-Gallo et al., Science 361, 479 (2018) 11. G. Grissonnanche et al., Nature 595, 667 (2021) 12. A. Legros et al. Nat. Phys. 15, 142 (2019) 13. B. Michon et al, Nat. Comm.14, 3033 (2023) 14. N. D. Mathur et al., Nature 394, 39 (1998) 15. N. Doiron-Leyraud et al., Phys. Rev. B 80, 214531 (2009) 16. S. Karahara et al., Phys. Rev. B 81, 184519 (2010) 17. A. Legros et al., Phys. Rev. B 106, 195110 (2022) 18. J. M. Harris et al., Phys. Rev. B 46, 14293 (1992) 19. M. Abdel-Jawad et al., Nat. Phys. 2, 821 (2006) 20. Y. Ando and T. Murayama, Phys. Rev. B 60, R6991 (1999)

Mercredi 27 Mai 2026, 11:45 à IHES, Amphithéâtre Léon Motchane	SEED (Seed Seminar of Mathematics and Physics)	math-ph
Cristina Anghel ( Université Clermont Auvergne )	TBA

Mercredi 27 Mai 2026, 13:30 à DPT-PHYS-ENS, ConfIV (E244) - 24 rue Lhomond 75005 PARIS	COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS)	physics
Laurent Bopp	The Perturbed Global Carbon Cycle: Recent Trends, Future Feedbacks, and Carbon Dioxide Removal techniques
Abstract:	Human activities have profoundly altered the global carbon cycle over the past century, driving a rapid increase in atmospheric CO₂ concentrations and reshaping the balance between carbon sources and sinks. In this presentation, I will first review the carbon budget of recent decades, highlighting the evolution of anthropogenic carbon emissions alongside the observed rise in atmospheric CO₂. This analysis underscores the essential buffering role played by natural carbon sinks, the ocean and the terrestrial biosphere, which have absorbed more than 50% of human-induced emissions and thereby slowed the rate of climate change. I will then examine the future evolution of these carbon sinks, with a particular focus on the ocean. The oceanic carbon sink emerges from complex couplings between physical circulation, chemical buffering, and biological processes. Changes in temperature, stratification, circulation, and ecosystem structure are expected to modify the efficiency of ocean carbon uptake in the coming decades. These processes point to the risk of a positive feedback between climate change and the carbon cycle, whereby warming reduces the capacity of natural sinks and amplifies the accumulation of CO₂ in the atmosphere. In a final section, I will critically assess several proposed interventions aimed at artificially enhancing the ocean carbon sink, including phytoplankton fertilization and ocean alkalinization. While these approaches are often presented as potential climate mitigation strategies, they raise significant scientific, environmental, and governance challenges, and their long-term effectiveness remains highly uncertain. Ultimately, understanding the dynamics, limits, and potential manipulation of natural carbon sinks is central to anticipating the trajectory of the Earth system and to designing robust and responsible climate mitigation pathways.

Mercredi 27 Mai 2026, 14:00 à CDF, Amphithéâtre Guillaume Budé (site Marcelin-Berthelot) ( 2e leçon )	COURS (Cours)	hep-th
Marc Henneaux ( Collège de France )	Limites non relativistes de la th\'eorie d'Einstein et applications
Abstract:	Th\'eorie de Newton-Cartan

Mercredi 27 Mai 2026, 14:00 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Kenji Nakanishi ( RIMS, Kyoto University & IHES )	Classification of Initial Data for Global Dynamics of Nonlinear Dispersive Equations (2/4)
Abstract:	Nonlinear dispersive equations are partial differential equations to describe various wave phenomena where the primary effects are wave dispersion and nonlinear interactions. Even a single equation can have many different types of solutions depending on the initial data, such as scattering, blow-up, and solitons. The theme of this course is to classify global behavior of solutions in terms of the initial data. More precisely, the problem is to characterize the set of initial data corresponding to each type of solutions, together with the configuration of those sets, which also requires to analyze transient evolutions during intermediate time. Despite the recent progress for the soliton resolution conjecture, which classifies the asymptotic behavior, its link to the initial data is much less understood, mostly restricted in the data size, types of behavior, and by symmetry of the equation or the solutions. The lecture will focus on two model cases as attempts to extend it in two directions. The first is to extend the initial data set to more variety of solutions; we consider the nonlinear Klein-Gordon equation and initial data near superposition of the ground state solitons, which are unstable. It is natural to expect that the classification is also a superposition of the single soliton case, but the interactions among unstable modes of different growth rates and large radiation from collapsed solitons can possibly spoil such a simple picture, by energy transfer from the most unstable mode to the others. I will show how to preclude it by using elementary geometry of the Lorentz transform and space-time weighted energy tailored for radiations from multi-solitons. The second is to extend the equations to less symmetry; we consider the Zakharov system, which is a system of the Schrodinger and the wave equations with Hamiltonian and mass conservation, but without the Galilei or Lorentz invariance, nor the center of mass or energy. Such loss of structure poses serious difficulty especially in proving the rigidity that the minimal non-dispersive solutions must be the ground states. I will show how to overcome it, by combining virial-variational estimates and space-time estimates for non-radiative source terms.

Mercredi 27 Mai 2026, 14:45 à IHES, Centre de conférences Marilyn et James Simons ( Séminaire Amplitudes et Gravitation sur l’Yvette (IHES/IPhT) )	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Aidan Herderschee ( IAS )	String Theory from Maximal Supersymmetry
Abstract:	I will study planar, maximally supersymmetric 4d EFTs that reduce to $\mathcal{N}=4$ SYM at low energies and show that novel constraints arise from the six-point amplitude. By constructing the six-scalar amplitude and imposing supersymmetry together with standard tree-level factorization, assuming parity-even scalar contact terms, I find striking nonlinear relations among the four-point Wilson coefficients. These relations collapse much of the naive EFT parameter space. When combined with positivity bounds from unitarity and causality, the allowed region in Wilson-coefficient space shrinks to a thin sliver converging on the open-superstring Veneziano amplitude, strongly suggesting that maximal supersymmetry singles out the tree-level string answer. More broadly, the result shows that higher-point amplitudes contain qualitatively new bounds on the space of EFTs, and that the space of consistent quantum field theories may be much smaller than current four-point analyses suggest.

Mercredi 27 Mai 2026, 16:00 à CDF, Amphithéâtre Guillaume Budé (site Marcelin-Berthelot)	SEM-EXCEP (Seminaire exceptionnel)	hep-th
Andrea Campoleoni ( Université de Mons )	Non-relativistic limits of massive (higher-spin) gravity and their condensed matter applications
Abstract:	Quantum Hall fluids provide an example of quantum matter where the bulk low-energy physics is governed by collective deformations of an incompressible fluid. Gapped excitations that behave as spin-2 objects under rotations have recently been observed experimentally, revealing a connection between collective dynamics and emergent geometry. This spin-2 mode is expected to be the first element in a broader hierarchy of higher-spin collective modes, encoding increasingly complex deformations of the quantum fluid. In the linearized regime, the spin-2 sector can be described by a Schrödinger-like action obtained from a non-relativistic limit of massive gravity. I will present a proposal for describing the linearized dynamics of collective modes of arbitrary spin based on non-relativistic limits of higher-spin actions, and discuss how this framework relates to observations supporting the existence of these modes.

Jeudi 28 Mai 2026, 14:00 à ESPCI, Room Holweck, building C, 1st floor, 10 rue Vauquelin, ESPCI ( Please contact seminaires-lpem@espci.fr for the zoom link )	SEM-EXCEP (Seminaire exceptionnel)	cond-mat
Marko Kralj ( Institute of physics, Zagreb, Croatia )	Epitaxial Growth of Next-Generation 2D Materials
Fichiers attachés:	Kralj_Paris-2026_abstract.pdf (125135 bytes)

Jeudi 28 Mai 2026, 14:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires)	physics
Giulia Isabella	Analyticity of the Black Hole S-Matrix
Abstract:	I will derive the analytic structure of the S-matrix for classical wave scattering on a Schwarzschild black hole in 4-dimensions. The argument relies on the analytic continuation of the gravitational potential, with the singularity behind the horizon playing a crucial role. We observe the emergence of Stokes phenomena leading to a surprising branch cut in the upper half plane, seemingly in tension with causality. I will discuss how this apparent paradox is solved and mention some bootstrap applications of these results.

Jeudi 28 Mai 2026, 14:00 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Kenji Nakanishi ( RIMS, Kyoto University & IHES )	Classification of Initial Data for Global Dynamics of Nonlinear Dispersive Equations (3/4)
Abstract:	Nonlinear dispersive equations are partial differential equations to describe various wave phenomena where the primary effects are wave dispersion and nonlinear interactions. Even a single equation can have many different types of solutions depending on the initial data, such as scattering, blow-up, and solitons. The theme of this course is to classify global behavior of solutions in terms of the initial data. More precisely, the problem is to characterize the set of initial data corresponding to each type of solutions, together with the configuration of those sets, which also requires to analyze transient evolutions during intermediate time. Despite the recent progress for the soliton resolution conjecture, which classifies the asymptotic behavior, its link to the initial data is much less understood, mostly restricted in the data size, types of behavior, and by symmetry of the equation or the solutions. The lecture will focus on two model cases as attempts to extend it in two directions. The first is to extend the initial data set to more variety of solutions; we consider the nonlinear Klein-Gordon equation and initial data near superposition of the ground state solitons, which are unstable. It is natural to expect that the classification is also a superposition of the single soliton case, but the interactions among unstable modes of different growth rates and large radiation from collapsed solitons can possibly spoil such a simple picture, by energy transfer from the most unstable mode to the others. I will show how to preclude it by using elementary geometry of the Lorentz transform and space-time weighted energy tailored for radiations from multi-solitons. The second is to extend the equations to less symmetry; we consider the Zakharov system, which is a system of the Schrodinger and the wave equations with Hamiltonian and mass conservation, but without the Galilei or Lorentz invariance, nor the center of mass or energy. Such loss of structure poses serious difficulty especially in proving the rigidity that the minimal non-dispersive solutions must be the ground states. I will show how to overcome it, by combining virial-variational estimates and space-time estimates for non-radiative source terms.

Jeudi 28 Mai 2026, 17:00 à UFR-PHYS-SU, Amphi 25 Campus Pierre-et-Marie-Curie, Jussieu	CPMC (Colloquium Pierre et Marie Curie)	physics.bio-ph
William Bialek ( Princetonn University )	Pushing the physical limits: optimization in living systems
Abstract:	TBA

Vendredi 29 Mai 2026, 12:00 à LPENS, E012 (salle des éléments)	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Paule Dagenais ( Institut Curie )	From Turing to Mechanical Folding: Rethinking Pattern Formation in Skin Appendages
Abstract:	Many biological patterns are thought to arise from Turing reaction–diffusion system, where morphogen interactions generate spatial organization, as seen in hair, feathers, and other skin appendages. However, not all patterns can be explained by chemical pre-patterning alone. In this talk, I will present the mammalian rhinarium (naked nose) as a case where patterning instead emerges from a mechanical self-organization process. Using volumetric imaging across development, we showed that polygonal grooves arise from constrained epidermal growth and buckling, with folds precisely aligned to an underlying network of stiff blood vessels. Numerical simulations reveal that these vessels act as rigid anchors that concentrate stress and set the characteristic length scale of the pattern. This supports the concept of mechanical positional information, whereby tissue mechanics locally guide an otherwise global self-organized process. Finally, analyses of genetical clones and pathological cases highlight the roles of stochasticity and altered material properties, emphasizing how mechanical and chemical frameworks provide complementary routes to biological pattern formation.

Vendredi 29 Mai 2026, 14:00 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Kenji Nakanishi ( RIMS, Kyoto University & IHES )	Classification of Initial Data for Global Dynamics of Nonlinear Dispersive Equations (4/4)
Abstract:	Nonlinear dispersive equations are partial differential equations to describe various wave phenomena where the primary effects are wave dispersion and nonlinear interactions. Even a single equation can have many different types of solutions depending on the initial data, such as scattering, blow-up, and solitons. The theme of this course is to classify global behavior of solutions in terms of the initial data. More precisely, the problem is to characterize the set of initial data corresponding to each type of solutions, together with the configuration of those sets, which also requires to analyze transient evolutions during intermediate time. Despite the recent progress for the soliton resolution conjecture, which classifies the asymptotic behavior, its link to the initial data is much less understood, mostly restricted in the data size, types of behavior, and by symmetry of the equation or the solutions. The lecture will focus on two model cases as attempts to extend it in two directions. The first is to extend the initial data set to more variety of solutions; we consider the nonlinear Klein-Gordon equation and initial data near superposition of the ground state solitons, which are unstable. It is natural to expect that the classification is also a superposition of the single soliton case, but the interactions among unstable modes of different growth rates and large radiation from collapsed solitons can possibly spoil such a simple picture, by energy transfer from the most unstable mode to the others. I will show how to preclude it by using elementary geometry of the Lorentz transform and space-time weighted energy tailored for radiations from multi-solitons. The second is to extend the equations to less symmetry; we consider the Zakharov system, which is a system of the Schrodinger and the wave equations with Hamiltonian and mass conservation, but without the Galilei or Lorentz invariance, nor the center of mass or energy. Such loss of structure poses serious difficulty especially in proving the rigidity that the minimal non-dispersive solutions must be the ground states. I will show how to overcome it, by combining virial-variational estimates and space-time estimates for non-radiative source terms.

Lundi 1 Juin 2026, 14:00 à LPNHE, Charpak	LPNHE (Séminaires du LPNHE)	physics
Yurii Maravin ( Kansas State University )	Highlights from the SMP results from CMS
Abstract:	The standard model continues to provide an exceptionally successful description of particle interactions at the electroweak scale, while precision measurements at the LHC increasingly probe its structure in extreme kinematic regimes. This talk presents recent highlights of the CMS standard model physics program using the Run 2 and Run 3 datasets. The talk will discuss the growing role of precision object reconstruction, advanced analysis techniques, and new methods to interpret results, providing essential inputs to searches for physics beyond the standard model.

Mardi 2 Juin 2026, 11:00 à IPHT, Amphi Claude Bloch, Bât. 774	IPHT-GEN (Séminaire général du SPhT)
Isabelle Gallagher ( Université Paris Cité )	TBA
Abstract:	TBA

Jeudi 4 Juin 2026, 14:00 à ESPCI, Room Holweck, building C, 1st floor, 10 rue Vauquelin, ESPCI ( Please contact seminaires-lpem@espci.fr for the zoom link )	SEM-EXCEP (Seminaire exceptionnel)	cond-mat
Antonio García-Martín ( Instituto de Micro y Nanotecnología IMN-CNM, CSIC (CEI UAM+CSIC), Madrid, Spain )	Nanophotonic Metasurfaces: VO2 Phase Control and qBIC-Enhanced Non-Reciprocity
Abstract:	see attached pdf file.
Fichiers attachés:	AbstractParis_AGM_2026.pdf (129289 bytes)

Jeudi 4 Juin 2026, 14:00 à LPTMC, campus Jussieu, couloir 12-13, 5ème étage, salle 5-23	SEM-EXCEP (Seminaire exceptionnel)	cond-mat
Alexander Hartmann ( Univ. Oldenburg )	Replica Symmetry breaking for Ulam's problem
Abstract:	The description of complex system by the concept of Replica Symmetry Breaking (RSB) was shaped by Giorgio Parisi in the 1980s to solve the mean-field spin glass, as honored by the Nobel price in 2021. RSB has been used to analyze systems such as spin glasses, neural networks, optimization problems, or machine learning. Unfortunaley, numerically these well know RSB-exhibiting problems are difficult since only exponential-time exact algorithms are available. Here two models are considered, directed polymers in random media and increasing subsequences, called Ulam's problem for the ground states, i.e. longest subsequences. The distributions of free energies or sequence lengths, respectively, exhibit complex large-deviation behavior, which can be numerically addressed by rare-event sampling algorithms. Furthermore, for both models it is possible to sample exactly in perfect thermal equilibrium with polynomial-time algorithms. This means, large system sizes are accessible, in contrast to, e.g., the case of spin glasses. The results from perfect sampling of some problem disorder ensembles indicate the presence of RSB with complex structured landscapes. Thus, the study of complex RSB behavior is conveniently accessible numerically for some models. Finally, for partially presorting random sequences, obe obtains a transition similar to a ferromagnet-spin glass transition.

Vendredi 5 Juin 2026, 13:00 à LPENS, Conf IV	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Mathis Guéneau ( MPI PKS )	TBA

Vendredi 5 Juin 2026, 14:00 à IHES, Amphithéâtre Léon Motchane ( Séminaire d'Analyse )	MATH-IHES (TBA)	math
Oleg Zaboronski ( University of Warwick )	Asymptotic Expansions for a Class of Fredholm Pfaffians and Interacting Particle Systems
Abstract:	Motivated by the phenomenon of duality for interacting particle systems we introduce two classes of Pfaffian kernels describing a number of Pfaffian point processes in the "bulk" and at the "edge". Using the probabilistic method due to Mark Kac, we prove two Szegő-type asymptotic expansion theorems for the corresponding Fredholm Pfaffians. The idea of the proof is to introduce an effective random walk with transition density determined by the Pfaffian kernel, express the logarithm of the Fredholm Pfaffian through expectations with respect to the random walk, and analyse the expectations using general results on random walks. We demonstrate the utility of the theorems by calculating asymptotics for the empty interval and non-crossing probabilities for a number of examples of Pfaffian point processes: coalescing/annihilating Brownian motions, massive coalescing Brownian motions, real zeros of Gaussian power series and Kac polynomials, and real eigenvalues for the real Ginibre ensemble. (Joint work with Will FitzGerald and Roger Tribe.)

Lundi 8 Juin 2026, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires)	physics
Mikhail Minin	Long-time, large-distance asymptotics of correlation functions of the Lieb?Liniger modelin thermal and non-thermal equilibrium
Abstract:	We study the long-time, large-distance asymptotic behaviour of dynamical two-point correlation functions of the Lieb?Liniger model in the limit of infinite repulsion (the one-dimensional impenetrable Bose gas). Starting with exact representations of correlation functions in terms of Fredholm determinants of an integrable integral operator, we perform the rigorous asymptotic analysis, using Riemann?Hilbert techniques. The integral operatordepends parametrically on time \(t\), distance \(x\) and on the filling fraction ? a function that characterizes the thermal or non-thermal equilibrium conditions. We consider a large class of non-thermal equilibrium conditions, extending previous results established for the thermal equilibrium case. The long-time and large-distance asymptotic behaviour is derived for two classes of filling fractions. These classes are characterized by the number of poles on the real axis (a generalization of Fermi points) that, together with the unique saddle point, contribute to the asymptotic expansion. For each class, we derive the long-time, large-distance symptotic behaviour as a series in \(x\)\(?1/2\) as \(x\) and \(t\) go to infinity for a fixed ratio \(x/t\). We provide explicit closed-form expressions for the leading and sub-leading terms, logarithmic corrections, and overall constants in terms of special functions and simple integrals. For the impenetrable Bose gas in thermal equilibrium, we verify the derived asymptotic expansions by comparing them with the existing results in the literature and with numerical data.This talk is based on joint work with Frank Göhmann, Karol K. Kozlowski, and Alexander Weiße.

Lundi 8 Juin 2026, 14:00 à IHES, Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets )	MATH-IHES (TBA)	math
Marc Burger ( ETH Zurich )	The Refined Toledo Invariant of a Non-Archimedean Surface Group Representation
Abstract:	Let S be a compact oriented surface with boundary, Γ its fundamental group, and G a simple algebraic group defined over Q such that the symmetric space associated to G(R) is Hermitian of tube type. Given a real closed field F and a canonical presentation of Γ, we define for a representation of Γ in G(F) an invariant taking values in an ordered abelian group A(F), called the refined Toledo invariant, as it generalizes the Toledo number in the case F = R. The group A(F) has a geometric interpretation as the group of signed areas for polygons in the Hilbert geometry associated to the upper half plane over F. The goal of the talk is to describe the construction of this invariant and to explain how it solves the problem of characterizing points in the real spectrum compactification of the space of maximal representations of Γ into G(R).

Lundi 8 Juin 2026, 14:00 à LPNHE, Salle des Seminaires	LPNHE (Séminaires du LPNHE)	physics
Jesse Thaler ( MIT )	QCD Theory meets Information Theory
Abstract:	What if we could make predictions for experimental measurements at the Large Hadron Collider based entirely on first-principles theoretical calculations? While this dream is hopelessly out of reach, we do have a growing catalog of precision calculations in quantum chromodynamics (QCD) as a well as increasingly accurate Monte Carlo generators. In this talk, I show how to leverage ideas from information theory and machine learning to merge these disparate QCD predictions into a unified theoretical prediction with associated uncertainties. Our strategy highlights the importance of logarithmic moments, which have not been previously studied in the QCD literature, either experimentally or theoretically.

Lundi 8 Juin 2026, 16:00 à IHES, Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets )	MATH-IHES (TBA)	math
Petra Schwer ( Universitat Heidelberg )	Conjugation in Affine Coxeter Groups and Beyond
Abstract:	Conjugacy classes in rank n affine Coxeter groups have a beautiful and simple geometric description in terms of their natural action on (n-1)-dimensional vector spaces. Moreover, one can locate the conjugating elements and centralizers in the vector space as well. These results allow to characterize the growth of the conjugator length function by geometric investigations.