Wednesday 15 January 2025, 14:45 at IHES, Amphithéâtre Léon Motchane ( Séminaire Amplitudes et Gravitation sur l’Yvette (IHES/IPhT) )	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Joon-Hwi Kim ( Caltech )	Newman-Janis Shift and Beyond
Abstract:	In this talk, it will be shown that the Kerr metric describes a pair of self-dual and anti-self-dual Taub-NUT instantons, like the N and S poles of a bar magnet. The implications of this fact will be discussed. Firstly, it derives the Newman-Janis algorithm without an ambiguity: a mathematical procedure that generates spinning black hole solutions from non-spinning ones by means of a complex transformation, previously believed as merely a formal construct. Secondly, it uniquely determines the effective point-particle Lagrangian of Kerr black hole in post-Minkowskian gravity, based on the topological nature of the gravitational Dirac string (Misner string) associated with the NUT charges. This off-shell construction resolves the longstanding struggle that the gravitational dynamics of Kerr black holes at the second post-Minkowskian order is not uniquely, or easily, determinable from the scattering amplitudes methods. The gravitational Compton amplitude for Kerr black hole will be presented, which achieves correct factorizations without spurious poles in a simple manner. Finally, a new chapter of relativity will be proposed, in which spin is intrinsically unified into spacetime: "spinspacetime”.

Thursday 16 January 2025, 10:00 at IHP, Grisvard (314)	RENC-THEO (Rencontres Théoriciennes)	hep-th
Celine Zwikel ( Perimeter Institute )	Symmetries of the gravitational scattering in the absence of peeling
Abstract:	The asymptotic structure of spacetime with a vanishing cosmological constant is central to discussing gravitational radiation and gravitational scattering. In asymptotically flat spacetimes, the peeling property prescribes a decay rate for the Weyl tensor as one approaches the null boundary. However, there are compelling motivations for relaxing this peeling condition, leading to a polyhomogeneous rather than polynomial expansion in Bondi gauge. In this talk, I will review these motivations and explore the implications of introducing logarithmic terms into the asymptotic expansion. I will discuss how these modifications affect the symmetry structure of such spacetimes and the consequences on soft theorems. Furthermore, I will present new logarithmic evolution equations and flux-balance laws, which point to the existence of an infinite hierarchy of subleading logarithmic soft graviton theorems. (based on 2407.07978 )

Thursday 16 January 2025, 11:00 at IHES, Amphithéâtre Léon Motchane	MATH-IHES (TBA)	math
Daxin Xu ( Morningside Center of Mathematics, Chinese Academy of Sciences & IHES )	Frobenius Structure on Theta Connections and Epipelagic Langlands Parameters
Abstract:	In this talk, we first review the local monodromy at infinity of the Bessel F-isocrystals following Dwork, Sperber. Then we explain a generalization of this story for theta connections. Theta connections are certain rigid connections over $P^1$ minus two points, related to epipelagic representations under the geometric Langlands correspondence. As an application, we verify a conjecture of Reeder-Yu on the epipelagic Langlands parameters under some technical conditions. The talk is based on my joint work with Xinwen Zhu and a work in progress with Lingfei Yi.

Thursday 16 January 2025, 11:45 at IHP, Grisvard (314)	RENC-THEO (Rencontres Théoriciennes)	hep-th
Connor Behan ( ICTP-SAIFR )	Making AdS_3 x S^3 more like AdS_5 x S^5
Abstract:	Holographic CFTs possess a certain point in moduli space where there is a weakly coupled gravity dual. Computing the first non-trivial term in a four-point function using this description used to involve tedious work but much of this has now been superseded by bootstrap methods. In the case of AdS_5 x S^5 supergravity, there are now compact expressions for infinitely many tree-level four-point functions and these have served as a stepping stone towards correlators with loops, stringy corrections and more external legs. AdS_3 x S^3 is another supergravity background with a close connection to known holographic CFTs but it has not yet been put on the same footing. In this talk, I will explain why the obstacles are less daunting than they used to be and how they can be overcome with a formalism based on multiple Mellin amplitudes.

Thursday 16 January 2025, 14:00 at LPTMC, Jussieu, towers 13-12, 5th floor, room 5-23, LPTMC seminar room	SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)	cond-mat
Benjamin Wieder ( IPhT Saclay )	Monopole Quantum Numbers and Projective Representations in Stable and Fragile Topological Crystalline Insulators
Abstract:	Over the past 15 years, a dizzying array of noninteracting topological insulator (TI) and topological crystalline insulator (TCI) phases have been theoretically predicted and identified in real materials. While the TI states are well understood, the TCI states – which comprise the majority of topological materials in nature – exhibit more complicated classification groups and boundary states and carry more ambiguous response signatures. For earlier variants of interacting symmetry-protected topological states (SPTs), both the classification and response were clarified through the many-body quantum numbers of the 0D collective excitations bound to crystal and electromagnetic defects, such as magnetic fluxes and monopoles. In particular, when 0D defects exhibit fractionalized quantum numbers, or more generally projective representations of the local many-body symmetry group, this can indicate the presence of quantized responses in the bulk that are governed by long-wavelength topological field theories that are stable to symmetric interactions. In this talk, I will introduce numerical methods for computing defect quantum numbers in stable and fragile TCI states via the reduced density matrix, revealing a deep connection between defect quantum numbers and the entanglement spectrum. Surprisingly, we find that when crystal symmetries are included in the local symmetry group, defects can appear to transform projectively even in Wannierizable (fragile) insulators, casting doubt on the suitability of magnetic monopoles for characterizing the TCI states present in real 3D materials. Our results represent a crucial step towards describing TCIs beyond tight-binding models and frameworks like “higher- order topology,” and facilitate more direct connections between free-fermion TCIs and interacting SPTs.

Thursday 16 January 2025, 14:00 at LPTM, 4.13b	SEM-LPTM-UCP (Seminaires du LPTM , Universite de Cergy Pontoise)	cond-mat.other
Max Mcginley ( Trinity College, Cambridge )	Measurement-induced entanglement and complexity in shallow 2D quantum circuits
Abstract:	There has been a great deal of recent interest in understanding how measurements can influence the dynamics of entanglement in many-body systems. In this talk, I will describe how long-ranged entanglement can be generated by measuring states prepared by constant-depth 2D quantum circuits. We introduce a new theoretical technique, based on ideas from multi-user quantum Shannon theory, which allows us to establish a rigorous lower bound on the amount of entanglement generated by measurements in this setting. Our method avoids the so-called replica approach–the main tool employed for studying such problems so far–which gives rigorous results only in the simplest of scenarios. Using this technique, we prove a recent conjecture about generic (random) 2D shallow circuits followed by measurements: Namely, that above some O(1) critical depth, extensive long-ranged measurement-induced entanglement is produced, even though the pre-measurement state is strictly short-ranged entangled. This result has consequences for the computational complexity of sampling from generic shallow-depth quantum circuits, and for the hardness of contracting random 2D tensor networks

Monday 20 January 2025, 14:00 at IJCLAB, 210/1-114 - Salle des Séminaires	IJCLAB-COSM (Seminar of the Gravity and cosmology group of IJCLAB)	gr-qc
Sébastien Renaux-Petel ( IAP )	New particles in the sky
Abstract:	The field of primordial non-Gaussianities is twenty years old. During that time, cosmologists have built a dictionary between the physics active during inflation and higher-order correlation functions of primordial density fluctuations. I will argue that this dictionary is far from complete, with theoretical predictions available only in restricted classes of theories. To fill in this gap, I will present the cosmological flow, a complete and systematic approach to compute inflationary correlators for all inflationary theories. This enables us to assist our theoretical understanding and to generate theoretical data for an unbiased interpretation of upcoming cosmological observations. I will explain that the cosmological collider signal, lying in soft limits of correlators, often described as a robust probe of the field content of inflation, is as robust as its assumptions are restrictive, and I will show its properties in theories involving multiple degrees of freedom, with strong mixing, in the presence of features, and with non-trivial sound speeds. Eventually, I will describe another signal that would reveal the existence of additional heavy fields in a simpler and complementary manner to the cosmological collider: the low-speed collider signal arises when the curvature perturbation propagates at a reduced speed of sound, and it is characterised by a resonance in mildly-soft kinematic configurations of correlators. It can be understood in terms of a single-field effective field theory, albeit one that breaks the usual assumption of locality. Besides, I will show that this framework can naturally accommodate parity violation when the extra field is spinning.

Monday 20 January 2025, 14:00 at IHES, Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets )	MATH-IHES (TBA)	math
Anne Parreau ( Université Grenoble Alpes )	Hilbert Geometry over Non-Archimedean Ordered Fields
Abstract:	I will explain how convex projective geometry over non-Archimedean ordered fields may be used to study large scale properties of individual real Hilbert geometries and degenerations of convex projective actions, using a projective geometry version of ultralimits. Non-Archimedean convex subsets have a naturally associated quotient Hilbert metric space. In the case of ultralimits, we show that it is the ultralimit of the real Hilbert metric spaces under a natural non-degeneracy condition. I will present some examples and give a full description of the Hilbert metric space for non-Archimedean polytopes defined over R, which correspond to the asymptotic cones of a fixed real polytope. This is joint work with Xenia Flamm.

Monday 20 January 2025, 16:00 at IHES, Amphithéâtre Léon Motchane ( Séminaire Géométrie et groupes discrets )	MATH-IHES (TBA)	math
Timothee Benard ( CNRS & Université Paris-Nord )	Diophantine Approximation and Random Walks on the Modular Surface
Abstract:	Khintchine's theorem is a key result in Diophantine approximation. Given a positive non-increasing function f defined over the integers, it states that the set of real numbers that are f-approximable has zero or full Lebesgue measure depending on whether the series of terms (f(n))n converges or diverges. I will present a recent work in collaboration with Weikun He and Han Zhang in which we extend Khintchine's theorem to any self-similar probability measure on the real line. The argument involves the quantitative equidistribution of upper triangular random walks on SL(2,R)/SL(2,Z).

Tuesday 21 January 2025, 10:45 at 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
Michel Fruchart ( Gulliver, ESPCI )	Pattern formation by turbulent cascades
Abstract:	Fully developed turbulence is a universal and scale-invariant chaotic state characterized by an energy cascade from large to small scales at which the cascade is eventually arrested by dissipation. Here we show how to harness these seemingly structureless turbulent cascades to generate patterns. Pattern formation entails a process of wavelength selection, which can usually be traced to the linear instability of a homogeneous state. By contrast, the mechanism we propose here is fully nonlinear. It is triggered by the non-dissipative arrest of turbulent cascades: energy piles up at an intermediate scale, which is neither the system size nor the smallest scales at which energy is usually dissipated. Using a combination of theory and large-scale simulations, we show that the tunable wavelength of these cascade-induced patterns can be set by a non-dissipative transport coefficient called odd viscosity, ubiquitous in chiral fluids ranging from bioactive to quantum systems. Odd viscosity, which acts as a scale-dependent Coriolis-like force, leads to a two-dimensionalization of the flow at small scales, in contrast with rotating fluids in which a two-dimensionalization occurs at large scales. Apart from odd viscosity fluids, we discuss how cascade-induced patterns can arise in natural systems, including atmospheric flows, stellar plasma such as the solar wind, or the pulverization and coagulation of objects or droplets in which mass rather than energy cascades.

Wednesday 22 January 2025, 11:00 at APC, 454A-Luc Valentin ( https://apc.u-paris.fr/APC_CS/fr/colloquium-apc-history-r-process )	APC-COLLOQUIUM (Colloquium de l'APC)	hep-th
James Lattimer ( State University of New York at Stony Brook )	The history of the r-process
Abstract:	The rich history of the r-process, which began with geochemists and involves more than a dozen Nobel laureates, is reviewed in this talk. The r-process is the mechanism by which half of all nuclei heavier than iron are created, and involves intense fluxes and rapid captures of neutrons. However, its astrophysical site has long been debated. The recent LIGO/VIRGO detection of gravitational radiation from GW170817 bears the clear signature of a binary neutron star merger and validated a number of theoretical predictions. These included the observations of a short gamma-ray burst 1.7s following the merger, and an extended optical/infrared afterglow lasting weeks. The afterglow is the predicted signal of radioactive decays from decompressing neutron-rich matter catastrophically ejected from the merging stars and provides solid evidence that neutron star mergers are a major, if not primary, source of r-process nuclei. Although this idea was proposed nearly 45 years ago by David Schramm and myself, it was largely ignored in favor of a supernova mechanism. Over the last decade, however, evidence has been accumulating in its favor. GW170817 may have finally settled this question, which has been one of the thorniest problems in nuclear physics and astrophysics. This talk presents my personal perspectives of this paradigm shift.

Wednesday 22 January 2025, 12:45 at LPENS, CdF (3 Rue d'Ulm)	LPENS-BQ (Balades Quantiques de le LPENS)	cond-mat.stat-mech
Alvise Bastianello ( TU Munich )	Bound states stabilization and generalized hydrodynamics in a one-dimensional attractive Bose gas
Abstract:	Ultracold quantum gases provide a versatile platform for exploring strong interactions and non-equilibrium phases with no equilibrium counterparts. These phenomena often surpass the computational reach of traditional numerical methods, necessitating innovative approaches. In this talk, I will discuss the experimental realization of the attractive one-dimensional Bose gas in highly non-equilibrium states, stabilized by approximate integrability. I will also introduce the theoretical framework of generalized hydrodynamics, a powerful tool for nearly-integrable systems that enables precise quantitative descriptions of these exotic phases. Ref Exp. [to appear]: M. Horvath, A. Bastianello, S. Dhar, R. Koch, Y.Guo, J.S. Caux, M. Landini, and H.-C. Nägerl. Ref Th.: R. Koch, A. Bastianello, J.-S. Caux, Phys. Rev. B 103, 165121 (2021).

Thursday 23 January 2025, 11:00 at LPTHE, LPTHE library	SEM-LPTHE (Séminaire du LPTHE)	hep-th
Dalimil Mazac ( IPhT )	TBA

Thursday 23 January 2025, 11:00 at IHES, Amphithéâtre Léon Motchane ( Séminaire de Géométrie Arithmétique )	MATH-IHES (TBA)	math
Guglielmo Nocera ( IHES )	Derived Azumaya Algebras and the Brauer Problem
Abstract:	The Brauer group ${\rm Br}(X)$ of an algebraic variety $X$ is defined as the group of Azumaya algebras on $X$ up to Morita equivalence. There is an injective map (the Brauer map) ${\rm Br}(X) \hookrightarrow {\rm H}^2_{\mbox{ét}} (X,{\mathbb G}_m)$. Understanding the image of this map constitutes the so-called Brauer problem. Toën introduced the notion of derived Azumaya algebra, later also developed by Lurie. Derived Azumaya algebras modulo Morita equivalence form the derived Brauer group dBr(X), which contains Br(X) and admits a map $\phi : {\rm Br}(X) \hookrightarrow {\rm H}^2_{\mbox{ét}} (X,{\mathbb G}_m)$ extending the classical Brauer map. Unlike that, however, $\phi$ is an isomorphism, and thus offers a natural way to describe those cohomology classes not contained in the image of the Brauer map. With Michele Pernice (KTH Stockholm) we gave a more concrete description of $\phi$ and its inverse, by using the interpretation of ${\rm H}^2_{\mbox{ét}} (X,{\mathbb G}_m)$ via ${\mathbb G}_m$-gerbes and by implementing the notion of twisted sheaves in the derived setting. I will explain this result and give some perspectives on ongoing work regarding the interaction of the derived Brauer group with Beilinson’s theory of adèles, in the case of a curve.

Thursday 23 January 2025, 14:00 at IHES, Amphithéâtre Léon Motchane	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Xinliang Lyu ( IHES )	Three-dimensional Real Space Renormalization Group with Well-controlled Approximations
Abstract:	Kadanoff’s block idea pioneers the renormalization group (RG) theory and clarifies the scaling hypothesis in critical phenomena. Nevertheless, it has difficulty as a quantitatively reliable RG method due to uncontrolled approximations when formulated in the spin language. Reformulated in a modern tensor-network language, the block idea is equipped with a natural measure of RG errors. In 2D, the RG errors are typically smaller than 1% and decrease systematically when more coupling constants are retained in the RG map. The relative error of the estimated free energy of the 2D Ising model can easily go down to about 10-9 using a personal computer. In 3D, due to the linear growth of entanglement entropy, the RG errors are too large for the block-tensor map to be reliable. For the 3D Ising model, the RG errors grow to more than 10% just after one RG step, and then keep growing to more than 30% near the critical fixed point. Even worse, the estimated scaling dimensions fail to converge with respect to the RG step. We propose an entanglement filtering (EF) scheme to cleanse the redundant entanglement. Enhanced by the proposed EF, the RG errors near the critical fixed point goes down to 6%; they decrease slowly to 2% when more couplings are retained. The estimated scaling dimensions become stable respect to the RG step. The relative errors of the first two relevant fields are 0.4% and 0.1% in the best case. The proposed RG is promising as a systematically-improvable real space RG method in 3D.

Thursday 23 January 2025, 14:00 at IJCLAB, Room A201	NUC-THEO (Séminaire de physique nucléaire théorique)	nucl-th
Mohamad Chamseddine ( IJCLab )	Dense matter properties within the chiral confining model
Abstract:	The properties of dense matter remain one of the most pursued topic of nuclear physics. Understanding them provides valuable insights into the fundamental interactions, and mainly QCD, which desribes the strong interaction. These conditions are also at the heart of many astrophysical phenomena such as neutron stars (NS), supernovae and the early universe. Although QCD is well established, understanding the state of matter at high densities-low temperatures is not straightforward; on one hand the strong interaction, unlike other interactions, is non-perturbative at these ``low'' energy regimes ($< 1 $GeV.fm-3), rendering the mathematical tools usually employed, such as perturbative approaches ineffective here. On the other hand we often rely on numerical approaches to problems in physics, in that case these are known as numerical lattice calculations, they work fine for finite temperatures, but encounter a problem at finite densities known as the sign problem. The consequence of this is that today, we have no theory in the regime of low temperature and high density that allows us to make experimental predictions, and this strongly motivates relying on effective modeling. In this talk, I will present a theoretical framework for the study of nuclear matter, known as the chiral confining model, that is anchored in two central phenomena in nuclear physics: chiral symmetry breaking and confinement. This model will be used within the relativistic Hartree-Fock (RHF) approach where chiral symmetry is represented by a scalar potential and the effect of confinement through the nucleon response. The predictions of this model will be discussed along with various improvements progressively added on top of the model.
Attachments:	Abstract.pdf (150051 bytes)

Monday 27 January 2025, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774	IPHT-STA (Séminaire de Physique Statistique, CEA/Saclay)	cond-mat.stat-mech
Francois Huveneers ( KCL )	Absence of Normal Transport in an Interacting Disordered Spin Chain
Abstract:	François Huveneers Kings College London Many-body localization (MBL) is an out-of-equilibrium phase of matter featuring emergent integrability: There exists a complete set of local integrals of motion. As a result, an MBL system remembers its initial state for arbitrarily long times if the system is thermally isolated. This implies, in particular, a total absence of transport. Demonstrating this with mathematical rigor proves highly challenging. In this talk, I will present a theorem stating that the diffusion constant of such systems vanishes, indicating that transport is at most sub-diffusive. An interesting aspect of the proof is that it relies on establishing MBL in some portions of the chains that are immune from resonances. Additionally, it rules out some numerical results that suggested MBL would not exist at all. Our work represents thus a step forward in rigorously establishing the existence of the MBL phase in one-dimensional systems. From a work with W. De Roeck, L. Giacomin and O. Prosniak.

Monday 27 January 2025, 14:00 at IJCLAB, 210/1-114 - Salle des Séminaires (IJCLab)	IJCLAB-COSM (Seminar of the Gravity and cosmology group of IJCLAB)	gr-qc
Francesco Del Porro ( Niels Bohr Institute )	TBA

Tuesday 28 January 2025, 10:45 at 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 Mangeolle ( TUM (Munich) )	Thermal Hall conductivity of neutral bosons from the quantum kinetic equation
Abstract:	Thermal Hall conductivity has recently emerged as an experimentally accessible property of insulating materials. Theoretical understanding thereof has remained a challenge, in particular since the breaking of time-reversal symmetry by neutral particles is nontrivial and can emerge from multiple mechanisms (semiclassical dynamics, skew-scattering, etc). In a first part, I will present a general formulation of inelastic skew-scattering of energy-carrying bosons by other collective excitations. Specializing to phonon-magnon interactions, I will show that a phonon thermal Hall effect from skew-scattering in antiferromagnets is allowed by magnetoelastic and spin-orbit couplings. In a second part, I will focus on the free semiclassical dynamics of neutral bosons, and present a systematic derivation of their kinetic equation, incorporating the topological dynamics of wavepackets in the form of Berry curvatures (generalized to phase space). This makes it possible to treat inhomogeneous systems, including boundaries, textures, etc., in a compact and natural manner.

Wednesday 29 January 2025, 12:45 at LPENS, 3 rue dUlm College de France	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Bertrand Delamotte ( LTPMC )	TBA

Thursday 30 January 2025, 17:00 at UFR-PHYS-SU, Amphi 25 Campus Pierre-et-Marie-Curie, Jussieu	CPMC (Colloquium Pierre et Marie Curie)	astro-ph|cond-mat|gr-qc|hep-ex|hep-lat|hep-ph|hep-th|physics|quant-ph
Bérengère Dubrulle ( SPEC Saclay, Académie des Sciences )	Turbulence et climat
Abstract:	TBA

Monday 3 February 2025, 10:30 at IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Laure Saint-Raymond ( IHES )	Hard Sphere Dynamics in the Low Density Limit (1/4)
Abstract:	At the microscopic level, a gas is a collection of interacting neutral particles. The very large number of degrees of freedom and the sensitivity of the system to very small perturbations mean that it is essentially impossible to predict its dynamics deterministically. At the end of the 19th century, Boltzmann proposed describing the behaviour of gas in an alternative way, using a statistical approach. A natural question is whether the assumption of statistical independence that underlies this model is compatible with microscopic dynamics and in what sense the Boltzmann equation is a good approximation. This course will provide some answers to this question, within the simplified framework of contact interactions. 1. The Boltzmann equation, the chaos hypothesis and the H theorem 2. Law of large numbers for the dynamics of hard spheres 3. Correlations, dynamic clusters 4. Fluctuations and large deviations for the dynamics of hard spheres

Tuesday 4 February 2025, 10:30 at IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Laure Saint-Raymond ( IHES )	Hard Sphere Dynamics in the Low Density Limit (2/4)
Abstract:	At the microscopic level, a gas is a collection of interacting neutral particles. The very large number of degrees of freedom and the sensitivity of the system to very small perturbations mean that it is essentially impossible to predict its dynamics deterministically. At the end of the 19th century, Boltzmann proposed describing the behaviour of gas in an alternative way, using a statistical approach. A natural question is whether the assumption of statistical independence that underlies this model is compatible with microscopic dynamics and in what sense the Boltzmann equation is a good approximation. This course will provide some answers to this question, within the simplified framework of contact interactions. 1. The Boltzmann equation, the chaos hypothesis and the H theorem 2. Law of large numbers for the dynamics of hard spheres 3. Correlations, dynamic clusters 4. Fluctuations and large deviations for the dynamics of hard spheres

Wednesday 5 February 2025, 10:30 at IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Laure Saint-Raymond ( IHES )	Hard Sphere Dynamics in the Low Density Limit (3/4)
Abstract:	At the microscopic level, a gas is a collection of interacting neutral particles. The very large number of degrees of freedom and the sensitivity of the system to very small perturbations mean that it is essentially impossible to predict its dynamics deterministically. At the end of the 19th century, Boltzmann proposed describing the behaviour of gas in an alternative way, using a statistical approach. A natural question is whether the assumption of statistical independence that underlies this model is compatible with microscopic dynamics and in what sense the Boltzmann equation is a good approximation. This course will provide some answers to this question, within the simplified framework of contact interactions. 1. The Boltzmann equation, the chaos hypothesis and the H theorem 2. Law of large numbers for the dynamics of hard spheres 3. Correlations, dynamic clusters 4. Fluctuations and large deviations for the dynamics of hard spheres

Wednesday 5 February 2025, 12:45 at LPENS, 3 rue dUlm, College de France	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Nina Javerzat ( LIPhy )	TBA

Thursday 6 February 2025, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage	SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques)	hep-th
Hyeonjun Park ( KIAS )	TBA

Thursday 6 February 2025, 14:00 at 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
Luca De Medici ( ESPCI )	TBA
Abstract:	TBA

Monday 10 February 2025, 13:30 at LPENS, U209	LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS)	cond-mat
Gwendal Fève ( LPENS )	TBA

Wednesday 12 February 2025, 10:30 at IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Laure Saint-Raymond ( IHES )	Hard Sphere Dynamics in the Low Density Limit (4/4)
Abstract:	At the microscopic level, a gas is a collection of interacting neutral particles. The very large number of degrees of freedom and the sensitivity of the system to very small perturbations mean that it is essentially impossible to predict its dynamics deterministically. At the end of the 19th century, Boltzmann proposed describing the behaviour of gas in an alternative way, using a statistical approach. A natural question is whether the assumption of statistical independence that underlies this model is compatible with microscopic dynamics and in what sense the Boltzmann equation is a good approximation. This course will provide some answers to this question, within the simplified framework of contact interactions. 1. The Boltzmann equation, the chaos hypothesis and the H theorem 2. Law of large numbers for the dynamics of hard spheres 3. Correlations, dynamic clusters 4. Fluctuations and large deviations for the dynamics of hard spheres

Wednesday 12 February 2025, 13:30 at DPT-PHYS-ENS, salle ConfIV (Département de Physique de l'ENS - 24 rue Lhomond 75005 PARIS)	COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS)	physics
Diamanti	TBA
Abstract:	TBA