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The SEMPARIS seminar webserver hosts annoucements of all seminars taking place in Paris area, in all topics of physics, mathematics and computer science. It allows registered users to receive a selection of announcements by email on a daily or weekly basis, and offers the possibility to archive PDF or Powerpoint files, making it available to the scientific community. [ More information ]
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| Wednesday 17 January 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Wednesday 17 January 2024, 13:30 at
IHP,
Maryam Mirzakhani (a.k.a. Salle 201 on 2nd floor) ( Kick-off event for the trimester "From discrete models to condensed matter". To attend in-person, register at: indico.math.cnrs.fr/event/11013/registrations. ) | SEED (Seed Seminar of Mathematics and Physics) | math-ph |
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| Abstract: | Recent years have seen a great deal of progress in understanding the behavior of bootstrap percolation (BP) models, a particular class of monotone cellular automata. In the initial configuration sites are occupied with probability p. The evolution of BP occurs at discrete times: empty sites stay empty and occupied sites are emptied iff a certain model dependent neighborhood is already empty. In the Euclidean lattice there is now a complete understanding of the large time evolution with a universality picture for the critical behavior. Much less is known for their non-monotone stochastic counterpart, namely kinetically constrained models (KCM). In KCM each vertex is updated independently at rate p (respectively 1-p) to occupied (respectively empty) iff it could be emptied in the next step by the bootstrap model. In the last two decades KCM have been the subject of intensive research both in physics and mathematics literature. The main motivation is that, for certain choices of the constraints, when p goes to zero KCM display some of the most striking features of the liquid/glass transition. Indeed, they were originally introduced in the 80's to support the free volume theories and later on used as the simplest lattice models reproducing the dynamical facilitation scenario. In this seminar I will discuss some recent rigorous results on the characteristic time scales of KCM as p goes to zero as well as the connection with the critical behavior of the corresponding BP models. | |
| Wednesday 17 January 2024, 15:00 at
IHP,
Maryam Mirzakhani (a.k.a. Salle 201 on 2nd floor) ( Kick-off event for the trimester "From discrete models to condensed matter". To attend in-person, register at: indico.math.cnrs.fr/event/11013/registrations. ) | SEED (Seed Seminar of Mathematics and Physics) | math-ph |
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| Abstract: | Consider a system of $N$ particles, described via a system of Stochastic Differential Equations (SDEs), interacting in a mean field way. We are interested in the limit, as $N$ goes to infinity, of this particle system, and try to derive from a microscopic point of view (i.e. particle dynamics) a mesoscopic point of view (i.e. a statistical description of the system). The notion of propagation of chaos refers to the phenomenon according to which, as the number of particles $N$ grows, two given particles become « more and more » statistically independent. The aim of this talk is to discuss more or less recent methods to prove this phenomenon for different types of particle systems, notably in singular Riesz-type interaction, with ideas ranging from Probability theory to analysis of Partial Differential Equations (PDEs). We focus in particular on quantitative and uniform in time propagation of chaos. This talk is based on joint works with A. Guillin (université Clermont-Auvergne) et P. Monmarché (Sorbonne Université). | |
| Wednesday 17 January 2024, 16:30 at
IHP,
Maryam Mirzakhani (a.k.a. Salle 201 on 2nd floor) ( Kick-off event for the trimester "From discrete models to condensed matter". To attend in-person, register at: indico.math.cnrs.fr/event/11013/registrations. ) | SEED (Seed Seminar of Mathematics and Physics) | math-ph |
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| Abstract: | The string-net models were introduced by Levin and Wen (1) as exactly solvable models of topological order in two dimensions. The latter appears in strongly interacting or frustrated systems and is characterized by the presence of point-like excitations, called anyons, with exotic (i.e. neither fermionic nor bosonic) exchange statistics. Built from a unitary fusion category, the string-net models realize a topological order corresponding to the Drinfeld center of the category. The energy spectrum of these models is trivial but the degeneracies are not. In particular, they depend on the genus of the surface on which the model is defined. After introducing the models, I will show how to compute these degeneracies and obtain the exact partition function of these models, opening the way to their study at finite temperature (2, 3). (1) M. A. Levin and X.-G. Wen, Phys. Rev. B 71, 045110 (2005) (2) J. Vidal, Phys. Rev. B 105, L041110 (2020) (3) A. Ritz-Zwilling, J.-N. Fuchs, J. Vidal, S. H. Simon, https://arxiv.org/abs/2309.00343 | |
| Thursday 18 January 2024, 11:00 at IHES, Amphithéâtre Léon Motchane | MATH-IHES (TBA) | math |
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| Abstract: | I will present a new theory of motivic cohomology for general (qcqs) schemes. It is related to non-connective algebraic K-theory via an Atiyah-Hirzebruch spectral sequence. In particular, it is non-A^1-invariant in general, but it recovers classical motivic cohomology on smooth schemes over a Dedekind domain after A^1-localisation. The construction relies on the syntomic cohomology of Bhatt-Morrow-Scholze and the cdh-local motivic cohomology of Bachmann-Elmanto-Morrow, and generalises the construction of Elmanto-Morrow in the case of schemes over a field. | |
| Thursday 18 January 2024, 11:00 at LPTHE, Library | SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) | math.QA |
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| Thursday 18 January 2024, 14:00 at LPTMC, ???? | SEM-EXCEP (Seminaire exceptionnel) | cond-mat |
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| Abstract: | TBA | |
| Thursday 18 January 2024, 14:30 at IHES, Amphithéâtre Léon Motchane | MATH-IHES (TBA) | math |
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| Abstract: | The notion of pseudo-representations was initially introduced for group algebras by Wiles (for GL2) and by Taylor (for GLd) in order to construct Galois representations associated to certain automorphic forms. Chenevier proposed an alternative theory of "determinant laws" which extends Wiles and Taylor’s definition to arbitrary rings. This theory has proved to be useful in the study of congruences between automorphic forms and in the deformation theory of residually reducible Galois representations. 
In this talk, I will present my joint work with Julian Quast on symplectic determinant laws, which adapts Chenevier’s framework to the symplectic group GSp2d. I will give the definition and highlight some of its key properties, and then explain its connection to Geometric Invariant Theory. In particular, I will show that in characteristic zero, the space of symplectic determinant laws recovers the GIT quotient of the space of symplectic representations by the conjugation action. | |
| Friday 19 January 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Monday 22 January 2024, 13:30 at LPENS, U207 (29 rue d'Ulm) | LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS) | cond-mat |
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| Tuesday 23 January 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Wednesday 24 January 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Thursday 25 January 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Friday 26 January 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Friday 26 January 2024, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-STA (Séminaire de Physique Statistique, CEA/Saclay) | cond-mat |
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| Tuesday 30 January 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Abstract: | In phases of condensed matter with broken continuous symmetries, as well as in fluids, transport processes generate irreversibility at the macroscale. To be complete, the hydrodynamic equations must include these dissipative effects. A fundamental question is to deduce all of them from the microscopic Hamiltonian dynamics of the particles with the methods of non-equilibrium statistical mechanics. In this presentation, a first-principle derivation based on a local-equilibrium approach is introduced. As an example of application, the crystalline solid is considered. The breaking of the three-dimensional continuous group of spatial translations implies the existence of three slow modes in addition to the five slow modes arising from the fundamental conservation laws of mass, energy, and linear momentum. Finally, based on the results of the local-equilibrium approach, the equilibrium and nonequilibrium properties relevant to the hydrodynamics of the perfect hard-sphere crystal are obtained with molecular dynamics simulations. | |
| Wednesday 31 January 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Friday 2 February 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Monday 5 February 2024, 13:30 at LPENS, U209 (29 rue d'Ulm) | LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS) | cond-mat |
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| Tuesday 6 February 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Wednesday 7 February 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Wednesday 7 February 2024, 13:30 at DPT-PHYS-ENS, ConfIV (E244) - Dépt de Physique de l'ENS - 24 rue Lhomond 75005 PARIS | COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS) | physics |
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| Abstract: | TBA | |
| Friday 9 February 2024, 10:15 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES : https://www.ihes.fr/evenements/#cours ) | MATH-IHES (TBA) | math |
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| Abstract: | The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows: 1. Light condensed abelian groups. 2. Analytic rings. 3. Analytic stacks. 4. Examples. | |
| Tuesday 20 February 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Abstract: | We consider a simple neural network model, evolving via non-linear coupled stochastic differential equations, where neural couplings are randomly asymmetric Gaussian variables with non-vanishing mean. We analyze the dynamics, averaged over the network ensemble, in the thermodynamic limit, using generating functional analysis. In the absence of noise, the fixed points of the dynamics can be characterized by two order parameters, namely the mean and variance of the neural activity, determined through a set of self- consistency equations, which close when couplings are fully asymmetric. These equations show that, for any degree of coupling asymmetry, two types of criticality emerge, corresponding to ferromagnetic and spin- glass order, respectively. The transition from the disordered phase to either of the ordered phases is consistent with spectral properties of the coupling matrix. Non-fixed point steady states are analysed for fully asymmetric interactions. Such solutions cannot be described by a closed set of equations for the stationary mean and variance, as the latter depends on a non-persistent order parameter, which quantifies time correlations in neural activity. This, in turn, evolves according to a gradient-descent dynamics on a potential, which depends on the variance itself. Our analysis reveals how the variance is dynamically selected by the system: whenever the potential is confining, so to allow a multitude of bounded steady-state solutions, the system selects the steady state corresponding to the separatrix curve. Chaotic motion is the manifestation, at the level of single network instances, of such ensemble-averaged dynamics laying on the curve that separates different realizable steady states. Finally, we show that when either the external signal or the noise exceed a certain threshold, that we calculate explicitly, the system is brought to a phase where only one bounded solution exists and chaos is suppressed. | |
| Wednesday 21 February 2024, 13:30 at DPT-PHYS-ENS, ConfIV (E244) - Dépt de Physique de l'ENS - 24 rue Lhomond 75005 PARIS | COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS) | physics |
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| Abstract: | TBA | |
| Thursday 29 February 2024, 14:00 at LPTMC, LPTHE library, Jussieu, towers 13-14, 4th floor???? | SEM-EXCEP (Seminaire exceptionnel) | cond-mat |
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| Abstract: | TBA | |
| Wednesday 6 March 2024, 13:30 at DPT-PHYS-ENS, ConfIV (E244) - Dépt de Physique de l'ENS - 24 rue Lhomond 75005 PARIS | COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS) | physics |
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| Abstract: | TBA | |
| Thursday 7 March 2024, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage | SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) | hep-th|math.AG |
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| Monday 11 March 2024, 13:30 at LPENS, U209 (29 rue d'Ulm) | LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS) | cond-mat |
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| Wednesday 13 March 2024, 12:45 at LPENS, 3 rue d Ulm, College de France | FORUM-ENS (Forum de Physique Statistique @ ENS) | cond-mat.stat-mech |
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| Abstract: | TBA | |
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