BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Département de mathématiques et applications - ECPv6.2.2//NONSGML v1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-ORIGINAL-URL:https://www.math.ens.psl.eu
X-WR-CALDESC:évènements pour Département de mathématiques et applications
REFRESH-INTERVAL;VALUE=DURATION:PT1H
X-Robots-Tag:noindex
X-PUBLISHED-TTL:PT1H
BEGIN:VTIMEZONE
TZID:Europe/Paris
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:20260329T010000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:20261025T010000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260604T120000
DTEND;TZID=Europe/Paris:20260604T130000
DTSTAMP:20260606T010045
CREATED:20260601T103907Z
LAST-MODIFIED:20260601T103907Z
UID:21783-1780574400-1780578000@www.math.ens.psl.eu
SUMMARY:Learning Monge Maps with Constrained Drifting Models
DESCRIPTION:The estimation of optimal transport maps (a.k.a. Monge maps) is a central problem in optimal transport literature. Recent observations reveal that the flow map of the Wasserstein gradient flow of the relative entropy closely approximates—though does not exactly equal—the Monge map between a given source distribution and a Gaussian target. In this work\, we demonstrate how the evolution equation governing this flow map can be corrected to form a constrained gradient flow that provably converges to the true Monge map.When the maps are parametrized as gradients of convex models (e.g. ICNN)\, we show that the resulting optimization scheme can be interpreted as a L²-natural gradient descent in the parameter space\, and that this approach is further connected to the recently introduced drifting generative models. On toy experiments\, we empirically illustrate the clear advantage of using that L²-natural gradient instead of the Euclidean for estimating Monge maps in this framework. \n\n\n\nJoint work with  T. Dumont and F.-X. Vialard\, https://arxiv.org/pdf/2603.25182
URL:https://www.math.ens.psl.eu/evenement/learning-monge-maps-with-constrained-drifting-models/
LOCATION:Salle W
CATEGORIES:CSD seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260602T120000
DTEND;TZID=Europe/Paris:20260602T130000
DTSTAMP:20260606T010045
CREATED:20260601T101208Z
LAST-MODIFIED:20260601T101650Z
UID:21779-1780401600-1780405200@www.math.ens.psl.eu
SUMMARY:ENS-Data Science colloquium - Rebecca Willett : How do simple rotations affect the implicit bias of Adam?
DESCRIPTION:Adaptive gradient methods such as Adam and Adagrad are widely used in = machine learning\, yet their effect on the generalization of learned = models =E2=80=93 relative to methods like gradient descent =E2=80=93 = remains poorly understood. Prior work on binary classification suggests = that Adam exhibits a =E2=80=9Crichness bias\,=E2=80=9D which can help it = learn nonlinear decision boundaries closer to the Bayes-optimal decision = boundary relative to gradient descent. However\, the coordinate-wise = preconditioning scheme employed by Adam renders the overall method = sensitive to orthogonal transformations of feature space. We show that = this sensitivity can manifest as a reversal of Adam=E2=80=99s = competitive advantage: even small rotations of the underlying data = distribution can make Adam forfeit its richness bias and converge to a = linear decision boundary that is farther from the Bayes-optimal decision = boundary than the one learned by gradient descent. To alleviate this = issue\, we show that a recently proposed reparameterization method =E2=80=93= which applies an orthogonal transformation to the optimization = objective =E2=80=93 endows any first-order method with equivariance to = data rotations\, and we empirically demonstrate its ability to restore = Adam=E2=80=99s bias towards rich decision boundaries. This is joint work = with Adela DePavia and Vasileios Charisopoulos. \n\n\n\n  \n\n\n\nThese seminars are being made possible through the support of the CFM-ENS Chair « Modèles et Sciences des Données ». \n\n\n\nThe organizers: Giulio Biroli\, Alex Cayco Gajic\, Bruno Loureiro\, Stéphane Mallat\, Gabriel Peyré.
URL:https://www.math.ens.psl.eu/evenement/ens-data-science-colloquium-rebecca-willett-how-do-simple-rotations-affect-the-implicit-bias-of-adam/
LOCATION:Amphi Jean Jaurès\, 29 rue d'Ulm\, PARIS\, 75005\, France
CATEGORIES:ENS-Data Science colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260529T110000
DTEND;TZID=Europe/Paris:20260529T120000
DTSTAMP:20260606T010045
CREATED:20260507T080030Z
LAST-MODIFIED:20260507T080031Z
UID:21694-1780052400-1780056000@www.math.ens.psl.eu
SUMMARY:Automath! Léo Dreyfus-Schmidt: AI tools for the working mathematician
DESCRIPTION:Recent AI systems are increasingly entering the working environment of mathematicians\, offering new ways to explore ideas\, search the literature\, and formalize arguments. In this talk\, we will present a selection of such tools\, focusing on their practical use in everyday mathematical work.
URL:https://www.math.ens.psl.eu/evenement/automath-leo-dreyfus-schmidt-ai-tools-for-the-working-mathematician/
LOCATION:campus de Jussieu (amphi 15)
CATEGORIES:Séminaire Automath
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260526T170000
DTEND;TZID=Europe/Paris:20260526T180000
DTSTAMP:20260606T010045
CREATED:20260518T082317Z
LAST-MODIFIED:20260518T112043Z
UID:21743-1779814800-1779818400@www.math.ens.psl.eu
SUMMARY:Quelques modèles de dynamique des populations: limites d'échelles
DESCRIPTION:Nous commencerons par introduire la notion de processus de Markov à sauts qui généralise les chaînes de Markov aux temps continus. Lorsque ces processus sont à valeurs vectorielles\, ils peuvent être réécrits sous forme d’équation différentielle stochastique. Ensuite\, le modèle logistique de Verlhust sera dérivé en tant que limite en grande population de ces modèles stochastiques. Dans le cas de populations évoluant sur un maillage discret\, la méthode permet de dériver des EDP de réaction-diffusion en faisant tendre la taille de la maille vers zéro ainsi que le nombre d’individus par maille vers l’infini. Enfin\, en étudiant le cas des processus de contact il est possible de dériver plus naturellement que dans les approches précédentes la notion de capacité de charge de l’environnement tout en se passant de l’hypothèse d’un grand nombre d’individus par maille. \n\n\n\n.
URL:https://www.math.ens.psl.eu/evenement/quelques-modeles-de-dynamique-des-populations-limites-dechelles/
LOCATION:Salle W
CATEGORIES:Colloquium doctorant
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260520T131500
DTEND;TZID=Europe/Paris:20260520T141500
DTSTAMP:20260606T010045
CREATED:20260401T122300Z
LAST-MODIFIED:20260518T081746Z
UID:21207-1779282900-1779286500@www.math.ens.psl.eu
SUMMARY:Rémi Coulon - Les géométries de Thurston : un peu d'illustration au service de la recherche
DESCRIPTION:Le théorème de géométrisation est un achèvement mathématique majeur du début du XXIème siècle. Il stipule\, grosso modo\, que toute variété topologique de dimension trois\, peut être comprise au moyen de huit géométries modèles\, appelées géométries de Thurston. Certaines d’entres elles sont familières des mathématiciennes et mathématiciens : la géométrie sphérique\, euclidienne\, ou hyperbolique. D’autres sont un plus étranges comme Nil ou Sol. Dans cet exposé on présentera un projet de visualisation (dans le prolongement des travaux de Pierre Berger) : que verrait-on si nous vivions dans l’une de ces géométries ? Au cours de cette promenade mathématique\, on verra comment la réalisation d’illustrations vient mettre à l’épreuve nos connaissances\, apporte un point de vue nouveau sur des sujets parfois anciens et soulève de nouvelles questions de recherche. \n\n\n\n\n\n\n\nSéminaires des Mathématiques
URL:https://www.math.ens.psl.eu/evenement/remi-coulon/
LOCATION:ENS — amphi Galois\, 45 rue d'Ulm\, Paris\, France
CATEGORIES:ANNÉE 2025-2026,Prochaine séance,Séminaire Des mathématiques
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260519T093000
DTEND;TZID=Europe/Paris:20260519T123000
DTSTAMP:20260606T010045
CREATED:20251018T115511Z
LAST-MODIFIED:20260511T081952Z
UID:20144-1779183000-1779193800@www.math.ens.psl.eu
SUMMARY:Vlad Vicol - On self-similar blowup in 3D incompressible fluids
DESCRIPTION:We discuss constraints on hypothetical finite-time (backwards) self-similar blow-up solutions for solutions of incompressible Euler and incompressible Navier-Stokes on R^3. In various situations\, we show that the very existence of a smooth similarity profile imposes strong restrictions on the similarity exponent. We also discuss new Liouville-type theorems for the viscous problem.
URL:https://www.math.ens.psl.eu/evenement/vlad-vicol/
LOCATION:Jussieu —  salle 15-16-309\, 4 Place Jussieu\, Paris\, 75005\, France
CATEGORIES:Séminaire Analyse non linéaire et EDP
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260518T000000
DTEND;TZID=Europe/Paris:20260520T235959
DTSTAMP:20260606T010045
CREATED:20260507T090720Z
LAST-MODIFIED:20260507T090939Z
UID:21709-1779062400-1779321599@www.math.ens.psl.eu
SUMMARY:Recent Progress on Self-Interacting Processes and Non-Reversible Monte Carlo
DESCRIPTION:Toutes les informations de la conférence sur la page de l’évènement \nAnthony Maggs: Large scale dynamics of non-reversible Monte Carlo algorithmsMonte Carlo simulation is a workhorse of the numerical study of physical systems at thermodynamic equilibrium. Non-reversible Monte Carlo algorithms replace the commonly used constraint of detailed balance with global balance. We give examples of situations where this leads to accelerated sampling of physical systems. We argue that the large-scale relaxation of such Event-Chain Monte Carlo methods is linked to the dynamics of the true self-avoiding walk. \nFrancis Lörler: Event Chain Monte Carlo\, self-repellent random walks\, and the stochastic heat equationThe Event Chain Monte Carlo algorithm is an MCMC method for sampling equilibrium configurations of interacting particles. When applied to a harmonic chain of oscillators\, it is closely related to the self-repellent random walk on a discrete circle. We show that these processes are second-order lifts of a discrete stochastic heat equation with additive noise. As a consequence\, we obtain a lower bound on the relaxation times of order n^{3/2}. Moreover\, we show that when the active particle is resampled with an appropriate rate\, then the relaxation time has an upper bound of order n^2. On the same model\, optimally tuned Hamiltonian Monte Carlo achieves a relaxation time of order n^{5/4}\, but due to the gradient evaluations\, its complexity is of order n^{9/4}. This confirms a conjecture of Werner Krauth that on this specific model\, ECMC can outperform HMC. Joint work with Andreas Eberle. \nBrune Massoulié: From the lifted TASEP to true self-avoiding walksThe lifted TASEP is a variant of the totally asymmetric exclusion process where at each time-step\, instead of trying to move forward a uniformly chosen particle\, a marked particle tries to move forward then may pass the marker to another particle. It was introduced by physicists as a toy model for non-reversible event-chain Monte-Carlo algorithms\, which are expected to reach equilibrium faster than reversible dynamics. We will study the behaviour of this system on the integer line by evidencing a connection with true self-avoiding walks\, yielding timescales of the dynamics. This is based on joint work with Clément Erignoux\, Werner Krauth\, François Simenhaus and Cristina Toninelli. \nFrancesco Coghi and Juan Garrahan: Self-interacting processes: from tensor networks to level 2.5 large deviationsIn this combined presentation\, we discuss two aspects of self-interacting processes (stochastic processes whose transition rates depend on empirical observables). First we show\, using a tensor network approach\, a connection to Doob conditioning\, such that Markov processes with constrained occupation measures are optimally realised by self-interacting dynamics. Second\, exploiting a natural separation of timescales\, we formulate the exact large deviation statistics for the joint empirical measure and flux\, thus extending the classical Markov theory to this non-Markovian setting. \nJonathon Peterson: Limit Theorems for self-interacting random walks: a Ray-Knight approachIn this talk I will discuss recent results\, joint with Kosygina\, Mareche\, and Mountford\, which show how one can use “joint Ray-Knight theorems” to prove functional limit laws for certain self-interacting random walks. Recent results of myself and co-authors have used these techniques to prove scaling limits for the “true” self-avoiding random walk and also for polynomially self-repelling random walks. For “true” self-avoiding walks we confirm a conjecture of Toth and Werner that the scaling limit is the “true” self-repelling motion. For polynomially self-repelling walks the scaling limit is a new process (the polynomially self-repelling motion) which has the same marginal distributions as a (1/2\, 1/2)-Brownian motion perturbed at its extrema\, but which has different joint distributions. \nLaure Marêché: Limit behavior for the self-repelling random walk with directed edgesThe self-repelling random walk with directed edges on Z was introduced by Tóth and Vető in 2008. It is a random walk with a memory\, such that the probability to cross a directed edge of Z is smaller if this edge was already crossed a lot in the past. Its definition resembles that of the more studied self-interacting random walks introduced by Tóth in 1994\,1995\,1996\, with directed edges instead of undirected edges. However\, this seemingly minor change yields a sharp difference in the behavior of the walk\, and the self-repelling random walk with directed edges on Z turns out to have very unusual properties\, which we will present in this talk. \nJulien Brémont: The memory of geometry in self-interacting random walks : eccentricity and flip statisticsObserving a particular set of visited sites strongly impacts the future for a self-interacting random walk\, as it conditions the past trajectory in a certain way. In one dimension\, the geometry of the past visited territory is described by the number of visited sites n\, and the eccentricity z\, that is the fraction of positive visited sites. How a certain geometry (n\,z) condition the future set of visited sites is a key question in understanding the impact of the past on future exploration. In this talk\, I will show how to answer this question for one-dimensional self-interacting random walks ; in particular\, I will use the Brownian web to compute the distribution of future geometry (n’\, z’) given (n\, z). \nPaul Pineau: Collective Behavior of Self-Interacting Random WalkersThe collective behavior of self-interacting random walkers (SIRWs)\, also known as trail-interacting particles\, gives rise to new challenges in both physics and mathematics. The shared spatial memory generated through their deposition process leads to complex interactions and emergent phenomena. From previous studies emerge two classes of SIRWs: one in which the interaction with the deposition field saturates (commonly referred to as SATW)\, and another in which the interaction field acts as a potential that grows linearly with deposition (known as TSAW). In this talk\, I will present recent results on systems of N mutually interacting random walkers belonging to these classes. \nBalint Veto: The Brownian web distanceThe random walk web distance is a natural directed distance on the trajectory of coalescing simple random walks. It is given by the minimal number of jumps between different random walk paths when one is only allowed to move forward in time. The Brownian web distance is the scale-invariant limit of the random walk web distance which can be described in terms of the Brownian web. It is integer-valued and has scaling exponents 0:1:2 as compared to 1:2:3 in the KPZ world. The shear limit of the Brownian web distance is still given by the Airy process. A weighted version of the random walk web distance converges to a new explicit distribution that interpolates between the Gaussian and the GUE Tracy-Widom distribution. Based on joint work with Balint Virag. \nRam Adar: Active remodeling in multicellular systemsCells constantly interact with their environment through both mechanical and chemical cues. Migrating cells\, for instance\, induce irreversible local changes in the density and organization of the surrounding extracellular matrix. We refer to this process as “active remodeling”. The remodeled environment biases subsequent cellular motion and can generate new forms of collective organization and dynamics. From a theoretical perspective\, this behavior can be described by the coupled dynamics of two fields: an active field undergoing reaction-diffusion dynamics\, and an environmental field that is locally enslaved to the active field. We will illustrate this framework in two settings. First\, we will show how active remodeling alters the emergence of nematic order in active systems\, motivated by extracellular matrix remodeling by fibroblast cells. Second\, we will show how the degradation of a confining environment leads to subdiffusive dynamics and may account for the expansion rate of cancer spheroids.
URL:https://www.math.ens.psl.eu/evenement/recent-progress-on-self-interacting-processes-and-non-reversible-monte-carlo/
LOCATION:Salle W (ENS)
CATEGORIES:Programme SP(A)M!
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260513T110000
DTEND;TZID=Europe/Paris:20260513T120000
DTSTAMP:20260606T010045
CREATED:20260511T082240Z
LAST-MODIFIED:20260511T082240Z
UID:21721-1778670000-1778673600@www.math.ens.psl.eu
SUMMARY:Amina Abdurrahman\, raconte-moi la topologie arithmétique !
DESCRIPTION:J’esquisserai comment des outils topologiques peuvent être utilisés dans la preuve de résultats arithmétiques en me concentrant sur les fonctions zêta en arithmétique et en topologie.En particulier\, je donnerai une formule cohomologique pour les fonctions L symplectiques du côté arithmétique\, dont la preuve repose de manière cruciale sur une formule similaire pour la torsion de Reidemeister des variétés de dimension 3 du côté topologique. Je donnerai également une perspective topologique sur l’ordre du groupe de Tate-Shafarevich.
URL:https://www.math.ens.psl.eu/evenement/amina-abdurrahman-raconte-moi-la-topologie-arithmetique/
LOCATION:Salle W toits du DMA
CATEGORIES:Algèbre et géométrie,Séminaire Raconte-moi
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260511T110000
DTEND;TZID=Europe/Paris:20260511T120000
DTSTAMP:20260606T010045
CREATED:20260507T082804Z
LAST-MODIFIED:20260507T082805Z
UID:21697-1778497200-1778500800@www.math.ens.psl.eu
SUMMARY:Brune Massoulié - An introduction to some self-repelling processes.
DESCRIPTION:Self-repelling walks and processes are stochastic processes that are influenced by their past behaviour\, in a way that makes them try to avoid their past trajectory. In this talk\, I will first present a toy model for self-repelling random walks introduced by Toth and Werner\, which allows to present results and methods that generalise to more complex models. I will then present the « true » self-avoiding walk (TSAW) and state the results from an article by Toth in 1995. Last\, I will informally present the « true » self-repelling motion\, which was constructed by Toth and Werner in 1998\, and was proved to be the limit of the TSAW very recently by Kosygina and Peterson.
URL:https://www.math.ens.psl.eu/evenement/brune-massoulie-an-introduction-to-some-self-repelling-processes/
LOCATION:Salle W (ENS)
CATEGORIES:Séminaire informel de probabilités
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260507T110000
DTEND;TZID=Europe/Paris:20260507T120000
DTSTAMP:20260606T010045
CREATED:20260430T081020Z
LAST-MODIFIED:20260430T081021Z
UID:21505-1778151600-1778155200@www.math.ens.psl.eu
SUMMARY:Gauthier Thurin\, Valérie Castin
DESCRIPTION:Gauthier Thurin – « Convergence Rates for Distribution Matching with Sliced Optimal Transport »Valérie Castin – « Balanced Low-Rank Adaptation: Removing Parameter Invariance to Accelerate Convergence »
URL:https://www.math.ens.psl.eu/evenement/gauthier-thurin-valerie-castin/
LOCATION:Salle W
CATEGORIES:CSD seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260506T140000
DTEND;TZID=Europe/Paris:20260506T170000
DTSTAMP:20260606T010045
CREATED:20260430T080415Z
LAST-MODIFIED:20260430T081156Z
UID:21503-1778076000-1778086800@www.math.ens.psl.eu
SUMMARY:Un après-midi de théorie des groupes - Elia Fioravanti\, Enrico Le Donne\, Catherine Pfaff
DESCRIPTION:14.00 – 14.45   Elia Fioravanti (KIT – Karlsruhe) « Generators for automorphisms of special groups »15.00 – 15.45   Enrico Le Donne (University of Fribourg) « Asymptotic geometry of Riemannian nilpotent groups »16.15 – 17.00   Catherine Pfaff (Queen’s University) « A « cubist » decomposition of the Handel-Mosher axis bundle » \n\n\n\n \n\n\n\nAbstracts: \n\n\n\nElia Fioravanti: Generators for automorphisms of special groups  \n\n\n\nGiven a family F of finitely generated groups\, do all groups in F have “tame” automorphisms\, or can there be “wild” examples? More concretely\, is Out(G) finitely generated for all groups G in the family F? Rips and Sela showed in the 90s that Out(G) is finitely generated for all Gromov-hyperbolic groups G\, while Baues and Grunewald showed in the 00s that Out(G) is arithmetic over Q (and hence finitely generated) for all virtually polycyclic groups G. This essentially exhausts our limited understanding of general phenomena of this kind\, with the structure of automorphisms of non-positively curved groups remaining a fundamental open problem. I will discuss the recent result that Out(G) is finitely generated for all (cocompact) special groups of Haglund and Wise. This is already new for most finite-index subgroups of right-angled Artin and Coxeter groups. \n\n\n\nEnrico Le Donne: Asymptotic geometry of Riemannian nilpotent groups. \n\n\n\nAsymptotic cones of Riemannian nilpotent Lie groups are Carnot groups. The volume of balls in Carnot groups grows exactly as a power of the radius. Heuristically\, the better the asymptotic cone approximates a Riemannian group\, the closer the volume growth approaches a polynomial growth. I will discuss several results obtained over the last few years in collaboration with Breuillard\, Nalon\, Nicolussi Golo\, and Ryoo. \n\n\n\nCatherine Pfaff: A “cubist” decomposition of the Handel-Mosher axis bundle \n\n\n\nA hyperbolic isometry acts on the compactified hyperbolic plane with North-South dynamics and a single invariant axis. The same is true for a pseudo-Anosov mapping class acting on a Teichmuller space and other hyperbolic-like settings. However\, while a fully irreducible free group outer automorphism acts on compactified Outer space with North-South dynamics\, there can be many axes for a single fully irreducible φ ∈ Out(F_r). With this in mind\, Handel and Mosher define the axis bundle for a fully irreducible φ ∈ Out(F_r). And then Handel-Mosher and Bridson-Vogtmann ask about the geometry of the axis bundle. In joint work with Chi Cheuk Tsang\, we show that the axis bundle of a nongeometric fully irreducible outer automorphism admits a canonical “cubist” decomposition into branched cubes that fit together with special combinatorics. From this structure\, we locate a canonical finite collection of periodic fold lines in each axis bundle. This can be considered as an analogue of results of Hamenstadt and Agol from the surface setting\, which state that the set of trivalent train tracks carrying the unstable lamination of a pseudo-Anosov map can be given the structure of a CAT(0) cube complex\, and that there is a canonical periodic fold line in this cube complex. Our “cubist” decomposition also gives a “hands on” solution to the fully irreducible
URL:https://www.math.ens.psl.eu/evenement/un-apres-midi-de-theorie-des-groupes-elia-fioravanti-enrico-le-donne-catherine-pfaff/
LOCATION:Salle W
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260506T131500
DTEND;TZID=Europe/Paris:20260506T141500
DTSTAMP:20260606T010045
CREATED:20260401T122545Z
LAST-MODIFIED:20260507T091846Z
UID:21204-1778073300-1778076900@www.math.ens.psl.eu
SUMMARY:Exemples d'approches de statistique pour le traitement de signal et les sciences du vivant
DESCRIPTION:Je présenterai dans cet exposé deux approches statistiques pour résoudre deux problèmes très différents : l’un en traitement du signal et l’autre en sciences du vivant. Plus précisément\, dans la première partie de cet exposé\, je présenterai un test de détection de rupture pour faire de la détection d’anomalies dans le trafic internet et dans la deuxième partie\, je présenterai une approche régularisée pour analyser des données de biologie moléculaire. \n\n\n\n\n\n\n\nSéminaires des Mathématiques
URL:https://www.math.ens.psl.eu/evenement/celine-levy-leduc/
LOCATION:ENS — amphi Galois\, 45 rue d'Ulm\, Paris\, France
CATEGORIES:ANNÉE 2025-2026,Séminaire Des mathématiques
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260506T110000
DTEND;TZID=Europe/Paris:20260506T120000
DTSTAMP:20260606T010045
CREATED:20260430T081744Z
LAST-MODIFIED:20260430T081744Z
UID:21515-1778065200-1778068800@www.math.ens.psl.eu
SUMMARY:Matteo Tamiozzo\, raconte-moi les groupes de Golod-Shafarevich !
DESCRIPTION:Les groupes de Golod-Shafarevich\, découverts dans les années 60\, ont trouvé des applications en théorie des nombres\, théorie des groupes et topologie. Dans cet exposé j’introduirai ces groupes\, et j’expliquerai le rôle qu’ils jouent dans l’étude des groupes fondamentaux des anneaux des entiers des corps de nombres et des variétés de dimension 3.
URL:https://www.math.ens.psl.eu/evenement/matteo-tamiozzo-raconte-moi-les-groupes-de-golod-shafarevich/
LOCATION:Salle W toits du DMA
CATEGORIES:Algèbre et géométrie,Séminaire Raconte-moi
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260504T160000
DTEND;TZID=Europe/Paris:20260504T170000
DTSTAMP:20260606T010045
CREATED:20260504T074450Z
LAST-MODIFIED:20260504T074451Z
UID:21610-1777910400-1777914000@www.math.ens.psl.eu
SUMMARY:Thomas Serafini
DESCRIPTION:.
URL:https://www.math.ens.psl.eu/evenement/thomas-serafini/
LOCATION:Salle W
CATEGORIES:Colloquium doctorant
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260427T140000
DTEND;TZID=Europe/Paris:20260427T150000
DTSTAMP:20260606T010045
CREATED:20260420T100943Z
LAST-MODIFIED:20260420T100944Z
UID:21334-1777298400-1777302000@www.math.ens.psl.eu
SUMMARY:Robin Khanfir - The Brownian tree is the only uniformly self-similar binary tree
DESCRIPTION:The Brownian tree is the scaling limit of many random tree models for which the square of the diameter is of the order of the number of vertices. In contrast to this universality\, proofs of such convergences commonly rely on model-specific methods. To provide a conceptual understanding of the universality of the Brownian tree\, we show that it is uniquely characterized by a uniform self-similar decomposition property. This leads to a general proof scheme for convergences to the Brownian tree that does not require the computation of finite-dimensional limit distributions. This talk is based on a work in progress.
URL:https://www.math.ens.psl.eu/evenement/robin-khanfir-the-brownian-tree-is-the-only-uniformly-self-similar-binary-tree/
LOCATION:Salle W (ENS)
CATEGORIES:Séminaire informel de probabilités
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260423T110000
DTEND;TZID=Europe/Paris:20260423T120000
DTSTAMP:20260606T010045
CREATED:20260420T090126Z
LAST-MODIFIED:20260420T090126Z
UID:21319-1776942000-1776945600@www.math.ens.psl.eu
SUMMARY:Beyond Uncertainty Sets: Leveraging Optimal Transport to Extend Conformal Predictive Distribution to Multivariate Settings
DESCRIPTION:Conformal prediction (CP) constructs uncertainty sets for model outputs with finite-sample coverage guarantees. A candidate output is included in the prediction set if its non-conformity score is not considered extreme relative to the scores observed on a set of calibration examples. However\, this procedure is only straightforward when scores are scalar-valued\, which has limited CP to real-valued scores or ad-hoc reductions to one dimension. The problem of ordering vectors has been studied via optimal transport (OT)\, which provides a principled method for defining vector-ranks and multivariate quantile regions\, though typically with only asymptotic coverage guarantees. We restore finite-sample\, distribution-free coverage by conformalizing the vector-valued OT quantile region. Here\, a candidate’s rank is defined via a transport map computed for the calibration scores augmented with that candidate’s score. This defines a continuum of OT problems for which we prove that the resulting optimal assignment is piecewise-constant across a fixed polyhedral partition of the score space. This allows us to characterize the entire prediction set tractably\, and provides the machinery to address a deeper limitation of prediction sets: that they only indicate which outcomes are plausible\, but not their relative likelihood. In one dimension\, conformal predictive distributions (CPDs) fill this gap by producing a predictive distribution with finite-sample calibration. Extending CPDs beyond one dimension remained an open problem. We construct\, to our knowledge\, the first multivariate CPDs with finite-sample calibration\, i.e.\, they define a valid multivariate distribution where any derived uncertainty region automatically has guaranteed coverage. We present both conservative and exact randomized versions\, the latter resulting in a multivariate generalization of the classical Dempster-Hill procedure.
URL:https://www.math.ens.psl.eu/evenement/beyond-uncertainty-sets-leveraging-optimal-transport-to-extend-conformal-predictive-distribution-to-multivariate-settings/
LOCATION:Salle W
CATEGORIES:CSD seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260422T131500
DTEND;TZID=Europe/Paris:20260422T141500
DTSTAMP:20260606T010045
CREATED:20260401T122700Z
LAST-MODIFIED:20260505T151040Z
UID:21201-1776863700-1776867300@www.math.ens.psl.eu
SUMMARY:Flots géodésiques\, à l’intersection entre géométrie\, topologie et dynamique
DESCRIPTION:Une métrique riemannienne sur une variété différentielle est un objet qui permet de mesurer des volumes\, et en particulier la longueur des courbes. Les courbes qui localement\, en un certain sens\, minimisent cette longueur sont appelées géodésiques. L’ensemble de ces courbes admet une caractérisation dynamique par un flot défini sur l’espace total du fibré tangent de la variété : le flot géodésique. Cette classe de systèmes dynamiques est parmi les plus célèbres : elle peut être considérée comme un modèle simplifié pour les systèmes hamiltoniens issus de la mécanique céleste\, et en même temps elle a inspiré le développement de plusieurs sujets en topologie et en dynamique\, notamment la théorie de Morse et la dynamique symplectique. Dans cet exposé\, je vais introduire les flots géodésiques\, et je ferai une promenade à travers l’histoire du sujet\, surtout pour les aspects concernant les orbites périodiques. \n\n\n\n\n\n\n\nSéminaires des Mathématiques
URL:https://www.math.ens.psl.eu/evenement/marco-mazzucchelli/
LOCATION:ENS — amphi Galois\, 45 rue d'Ulm\, Paris\, France
CATEGORIES:ANNÉE 2025-2026,Séminaire Des mathématiques
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260420T160000
DTEND;TZID=Europe/Paris:20260420T170000
DTSTAMP:20260606T010045
CREATED:20260420T084734Z
LAST-MODIFIED:20260421T074741Z
UID:21313-1776700800-1776704400@www.math.ens.psl.eu
SUMMARY:Gaspar Gomez - Trois exemples élémentaires de renormalisation
DESCRIPTION:La renormalisation est un concept flou\, qui provient de la physique théorique et qui est aujourd’hui abondamment étudié en mathématiques. La renormalisation peut être déroutante: il peut par exemple s’agir de retirer des quantités infinies dans des équations pour qu’elles soient bien posées. N’étant pas un spécialiste de la question\, je ne vous présenterai pas une approche générale mais plutôt trois exemples très élémentaires\, qui je l’espère\, vous rendront familier de ce concept et surtout le démystifieront. Le premier est déterministe\, il s’agit de la distribution valeur principale. Le second est probabiliste : ce sont les processus stables qui généralisent le mouvement brownien. Selon le temps\, je vous parlerai ensuite d’un troisième exemple: l’équation de la chaleur stochastique avec bruit multiplicatif. \n\n\n\n.
URL:https://www.math.ens.psl.eu/evenement/mael-laoufi-trois-exemples-elementaires-de-renormalisation/
LOCATION:Salle W
CATEGORIES:Colloquium doctorant
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260415T110000
DTEND;TZID=Europe/Paris:20260415T120000
DTSTAMP:20260606T010045
CREATED:20260410T085407Z
LAST-MODIFIED:20260410T085408Z
UID:21253-1776250800-1776254400@www.math.ens.psl.eu
SUMMARY:Conformal Prediction for Uncertainty Quantification in Machine Learning: Recent Advances
DESCRIPTION:Machine learning models are often seen as black-box systems that output point predictions without indicating how confident they are in those predictions. Recently\, Conformal Prediction (CP) has emerged as a powerful framework to address this issue by transforming point predictions into set-valued predictions with probabilistic guarantees. In this talk\, I will introduce CP and briefly present some key challenges and recent advances in the area. I will first discuss how to perform CP in a Federated Learning setting\, showing that a single round of communication is sufficient to match the performance of centralized approaches. I will then turn to the question of efficiency control in CP\, where finite-sample guarantees can be obtained by viewing CP as a minimum-volume set estimation problem. \n\n\n\nThis talk is based on the following papers:  \n\n\n\nP. Humbert\, B. Le Bars\, A. Bellet\, S. Arlot. One-Shot Federated Conformal Prediction\, ICML 2023 \n\n\n\nP. Humbert\, B. Le Bars\, A. Bellet\, S. Arlot. Marginal and Training-Conditional Guarantees in One-Shot Federated Conformal Prediction\, Arxiv preprint 2024 \n\n\n\nB. Le Bars\, P. Humbert. On Volume Minimization in Conformal Regression\, ICML 2025
URL:https://www.math.ens.psl.eu/evenement/conformal-prediction-for-uncertainty-quantification-in-machine-learning-recent-advances/
LOCATION:Salle W
CATEGORIES:CSD seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260413T110000
DTEND;TZID=Europe/Paris:20260413T120000
DTSTAMP:20260606T010045
CREATED:20260407T123429Z
LAST-MODIFIED:20260407T124734Z
UID:21247-1776078000-1776081600@www.math.ens.psl.eu
SUMMARY:Serte Donderwinkel - Counting connected graphs
DESCRIPTION:How many connected graphs have a prescribed degree sequence?This classical combinatorial question turns out to admit a natural probabilistic approach. \nIn joint ongoing work with Sasha Bell and Remco van der Hofstad\, we derive asymptotic formulas for the number of connected graphs with a given degree sequence. Our approach is an example of the probabilistic method: rather than counting directly\, we introduce a suitable random graph model and study the likelihood that it exhibits a desired structure. \nConcretely\, we construct a random graph in which (an approximation of) the prescribed degree sequence appears with high probability inside a large connected component. This perspective allows us to translate questions about enumeration into probabilistic statements about random graphs. \nAlong the way\, I will discuss several key probabilistic tools\, including the configuration model\, branching process approximations\, and local weak convergence\, and explain how they combine to yield asymptotic counting results.
URL:https://www.math.ens.psl.eu/evenement/serte-donderwinkel-counting-connected-graphs/
LOCATION:Salle W (ENS)
CATEGORIES:Séminaire informel de probabilités
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260409T124500
DTEND;TZID=Europe/Paris:20260409T134500
DTSTAMP:20260606T010045
CREATED:20260326T102406Z
LAST-MODIFIED:20260326T102534Z
UID:21172-1775738700-1775742300@www.math.ens.psl.eu
SUMMARY:ENS-Data Science colloquium - Michael Chertkov : Samples That Cooperate\, Samples That Remember: Two Exactly Solvable Bridge Diffusions
DESCRIPTION:Diffusion-based generative models treat samples as independent and memoryless. I will show that relaxing each assumption leads to rich\, exactly solvable physics — with no neural networks anywhere.Giving samples a present — coupling them through their evolving mean field — produces a McKean–Vlasov optimal transport problem whose self-consistent guidance is provably the linear interpolant between endpoint means\, for arbitrary distributions and any interaction schedule; applied to building-fleet demand response\, this saves 20%+ in actuation energy.Giving samples a past produces a continual-learning agent whose memory is a Bridge Diffusion and whose forgetting — arising from a single lossy temporal coarse-graining step — obeys a universal linear capacity law with a Shannon-like constant.Both constructions live in the world of Riccati equations\, hyperbolic functions\, and mixture linear algebra; the physics of the bridge — not the expressivity of a network — controls what is achievable. \n\n\n\n  \n\n\n\nThese seminars are being made possible through the support of the CFM-ENS Chair « Modèles et Sciences des Données ». \n\n\n\nThe organizers: Giulio Biroli\, Alex Cayco Gajic\, Bruno Loureiro\, Stéphane Mallat\, Gabriel Peyré.
URL:https://www.math.ens.psl.eu/evenement/ens-data-science-colloquium-michael-chertkov-samples-that-cooperate-samples-that-remember-two-exactly-solvable-bridge-diffusions/
LOCATION:ENS Salle Dussane
CATEGORIES:ENS-Data Science colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260408T140000
DTEND;TZID=Europe/Paris:20260408T170000
DTSTAMP:20260606T010045
CREATED:20260403T082003Z
LAST-MODIFIED:20260403T082112Z
UID:21215-1775656800-1775667600@www.math.ens.psl.eu
SUMMARY:Un après-midi de théorie des groupes - Adrien Boyer\, Julien Marché\, Greg Patchell
DESCRIPTION:14:00-14:45 Adrien Boyer (IMJ-PRG): Property RD and Boundary Representations for A2 Buildings  \n\n\n\n15:00-15:45 Julien Marché (ENS – PSL): Action of endomorphisms of free groups on their SL_2-character varieties  \n\n\n\n16:15-17:00 Greg Patchell (University of Oxford): Selfless Inclusions of C*-Algebras and Quantum Groups \n\n\n\n \n\n\n\nAbstracts: \n\n\n\nGreg Patchell: Selfless Inclusions of C*-Algebras and Quantum Groups \n\n\n\nRecently\, strong asymptotic freeness\, or selflessness\, in C-algebras has emerged as a powerful technique to prove important regularity properties including simplicity\, unique trace\, stable rank 1\, and strict comparison. In particular\, in Fall 2024\, Amrutam\, Gao\, Kunnwalkam Elayavalli\, and I showed that the reduced group C-algebras of all hyperbolic groups with trivial finite radical are selfless\, which resolved the open problem of strict comparison for the reduced group C-algebra of the free group on two generators. Since then\, our result has been expanded to include a much larger class of groups. Work has also begun on isolating selflessness for C-algebras not arising from groups\, including the result of Hayes\, Kunnawalkam Elayavalli\, and Robert on selflessness of the reduced free product of a large class of C-algebras (see also Flores-Klisse-Ó Cobhthaigh-Pagliero). I will introduce the general notion of a selfless inclusion of C-algebras\, with which we will see the selflessness of the reduced unitary compact matrix quantum groups. This work is joint with Ben Hayes\, Srivatsav Kunnawalkam Elayavalli\, and Leonel Robert. \n\n\n\n \n\n\n\nAdrien Boyer: Property RD and Boundary Representations for A2 Buildings \n\n\n\nI will discuss an approach based on boundary representations to prove property RD for discrete groups acting properly and cocompactly on affine buildings of type A2. This result is due to Robertson\, Ramagge\, and Steger in the late 1990s. I will emphasize geometric arguments involving the Furstenberg boundary that can be used to establish property RD\, in particular the notion of “foldings” or “confluences\,” as suggested by V. Kaimanovich. Along the way\, I will also mention a conjecture of Robertson\, Ramagge\, and Steger concerning the optimal bound\, and propose a possible approach toward resolving it. If time permits\, I will also explain what happens in the C2 case. This is joint work with Thang Nguyen. \n\n\n\n \n\n\n\nJulien Marché: Action of endomorphisms of free groups on their SL_2-character varieties. \n\n\n\nLet phi : F_n->F_n be an endomorphism and let phi^* denote its action on the character variety X_n=Hom(F_n\,SL_2(C))/SL_2(C). Cantat-Gelander-Souto raised the question whether phi^* is an automorphism of the affine variety X_n if and only if phi is an automorphism of F_n. I will describe work in progress which relates directly this question to the action of endomorphisms on the outer space CV_n through a compactification of X_n with special valuations.
URL:https://www.math.ens.psl.eu/evenement/un-apres-midi-de-theorie-des-groupes-adrien-boyer-julien-marche-greg-patchell/
LOCATION:Salle W
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260408T110000
DTEND;TZID=Europe/Paris:20260408T120000
DTSTAMP:20260606T010045
CREATED:20260402T124328Z
LAST-MODIFIED:20260402T124444Z
UID:21211-1775646000-1775649600@www.math.ens.psl.eu
SUMMARY:Basile Morando\, raconte-nous les groupes de Neretin !
DESCRIPTION:Les groupes de Neretin ont été définis par Yuri Neretin au début des années 90\, à l’origine comme analogues p-adiques du groupe des difféomorphismes du cercle. Depuis la preuve de leur simplicité par Kapoudjian en 1999\, ces groupes (localement compacts et totalement discontinus) suscitent un intérêt croissant: ils présentent de remarquables propriétés qui contrastent avec celles des groupes localement compacts simples connexes. Dans cet exposé\, on s’intéressera notamment au fait qu’ils n’admettent aucun réseau\, ainsi qu’aux propriétés remarquables de leurs représentations unitaires.
URL:https://www.math.ens.psl.eu/evenement/basile-morando-raconte-nous-les-groupes-de-neretin/
LOCATION:Salle W toits du DMA
CATEGORIES:Algèbre et géométrie,Séminaire Raconte-moi
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260408T093000
DTEND;TZID=Europe/Paris:20260408T103000
DTSTAMP:20260606T010045
CREATED:20260403T083819Z
LAST-MODIFIED:20260403T083820Z
UID:21217-1775640600-1775644200@www.math.ens.psl.eu
SUMMARY:Brisures de symétrie\, distributions et double quotients
DESCRIPTION:Soit G′ ⊂ G une paire de groupes et (V\, π) une représentation de G. Les problèmes de branchements consistent à étudier le comportement de la restriction π|G′ de π à G′. Dans le cas où V est un espace de Hilbert\, π est unitaire et G\, G′ sont localement compacts (par exemple des groupes de Lie)\, un théorème de Mautner implique que π|G′ se décompose (de manière unique si G′ est de type I) en intégrale directe de représentations irréductibles de G′. Lorsque π n’est pas unitaire (par exemple si π est une représentation lisse d’un groupe de Lie)\, une telle décomposition en irréductibles n’existe pas. Dans ce contexte plus général\, l’étude de π|G′ peut se faire à travers les espaces d’opérateurs de brisure de symétrie\, c’est-à-dire les espaces Hom_G′(π\, τ) où τ parcourt une classe appropriée de représentations de G. Dans le cas où G et G′ sont des groupes de Lie réductifs réels (par exemple (G\, G′) = (GL(n+1\, R)\, GL(n\, R)))\, une classe de représentations raisonnable de G et G′ est donnée par les représentations de leur série principale\, représentations obtenues par induction parabolique et donc géométriquement à partir de fibrés vectoriels homogènes. Dans cet exposé\, nous verrons à travers des exemples comment et pourquoi les distributions\, couplées à un certain double quotient\, fournissent un angle d’attaque redoutable pour l’étude des problèmes de branchement des groupes de Lie réductifs réels. \n\n\n\n.
URL:https://www.math.ens.psl.eu/evenement/brisures-de-symetrie-distributions-et-double-quotients/
LOCATION:Salle W
CATEGORIES:Colloquium doctorant
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260407T093000
DTEND;TZID=Europe/Paris:20260407T123000
DTSTAMP:20260606T010045
CREATED:20251018T115430Z
LAST-MODIFIED:20260326T185638Z
UID:20142-1775554200-1775565000@www.math.ens.psl.eu
SUMMARY:Computer-Assisted Proofs of 3D Euler Singularity and Nonuniqueness of Leray–Hopf Solutions for the Unforced 3D Navier–Stokes Equations
DESCRIPTION:Speaker: Thomas Hou (Caltech) \n\n\n\nThe talk will take place in « Amphithéâtre Galois »\, underground near the math library\, 45 rue d’Ulm\, Paris \n\n\n\nWhether the 3D incompressible Euler equations can develop a finite-time singularity from smooth initial data remains one of the central open problems in nonlinear PDEs. In this talk\, I will present recent joint work with Dr. Jiajie Chen\, in which we rigorously prove finite-time blowup for the 2D Boussinesq equations and the 3D axisymmetric Euler equations with smooth initial data and smooth boundary. Our approach uses a dynamically rescaled formulation that reduces singularity formation to the long-time stability of an approximate self-similar blowup profile. A key difficulty is proving the linear stability of a numerically constructed profile. To address this\, we decompose the solution operator into a leading-order part\, which admits sharp stability estimates\, and a finite-rank perturbation\, which is controlled by a computer-assisted proof. I will also discuss recent joint work with Yixuan Wang and Changhe Yang on nonuniqueness of Leray–Hopf solutions to the unforced 3D incompressible Navier–Stokes equations. In this setting\, the viscous term introduces several new ingredients but also greatly simplifies the analysis: standard $H^1$ estimates suffice\, without the singular weights needed in the inviscid case. A central step is to establish the existence of a self-similar Leray–Hopf solution and then prove the existence of a second solution by analyzing the stability of the linearized operator around this profile and showing that it admits an unstable mode. These results highlight the fruitful interplay among analysis\, computation\, and rigorous validation in nonlinear PDEs.
URL:https://www.math.ens.psl.eu/evenement/thomas-hou/
LOCATION:ENS — amphi Galois\, 45 rue d'Ulm\, Paris\, France
CATEGORIES:Séminaire Analyse non linéaire et EDP
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260326T110000
DTEND;TZID=Europe/Paris:20260326T120000
DTSTAMP:20260606T010045
CREATED:20260320T134419Z
LAST-MODIFIED:20260320T134419Z
UID:21149-1774522800-1774526400@www.math.ens.psl.eu
SUMMARY:Geometry-induced regularization and identifiability of deep ReLU networks
DESCRIPTION:La première partie de l’exposé présentera\, à l’aide d’un exemple simple et didactique\, les résultats mathématiques développés dans la seconde partie\, de manière à en rendre l’intuition accessible au plus grand nombre.  \n\n\n\nDu fait d’une régularisation implicite qui favorise les « bons » réseaux\, les réseaux de neurones avec un grand nombre de paramètres ne surapprennent généralement pas. Parmi les phénomènes connexes et encore mal compris figurent les propriétés des minima plats\, les dynamiques de type saddle-to-saddle et l’alignement des neurones. Pour analyser ces phénomènes\, nous étudions la géométrie locale des réseaux de neurones ReLU profonds. Nous montrons que\, pour une architecture fixée\, lorsque les poids varient\, l’image d’un échantillon X forme un ensemble dont la dimension locale change. L’espace des paramètres est ainsi partitionné en régions où cette dimension locale demeure constante. La dimension locale est invariante par rapport aux symétries naturelles des réseaux ReLU (c’est-à-dire les changements d’échelle positifs et les permutations de neurones).  \n\n\n\nNous établissons ensuite que la géométrie du réseau induit une régularisation\, la dimension locale constituant une mesure clé de régularité. De plus\, nous relions la dimension locale à une nouvelle notion de platitude des minima ainsi qu’aux dynamiques saddle-to-saddle. Pour les réseaux à une couche cachée\, nous montrons également que la dimension locale est liée au nombre de régions linéaires perçues par $X$\, ce qui éclaire sur l’effet de la régularisation. Ce résultat est étayé par des expériences et mis en relation avec l’alignement des neurones. Enfin\, je présenterai des expériences sur la base MNIST\, qui mettent en évidence la régularisation induite par la géométrie dans ce contexte. Finalement\, je ferai le lien entre des propriétés sur la dimension locale et l’identifiabilité locale des paramètres du réseau.
URL:https://www.math.ens.psl.eu/evenement/geometry-induced-regularization-and-identifiability-of-deep-relu-networks/
LOCATION:Salle W
CATEGORIES:CSD seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260325T131500
DTEND;TZID=Europe/Paris:20260325T141500
DTSTAMP:20260606T010045
CREATED:20260323T092619Z
LAST-MODIFIED:20260401T122403Z
UID:21161-1774444500-1774448100@www.math.ens.psl.eu
SUMMARY:Pseudo-aléa des chiffres des nombres premiers
DESCRIPTION:Les chiffres des nombres premiers sont-ils « aléatoires » ? Ont-ils des propriétés semblables à celles des chiffres de tous les entiers naturels ? Ces questions\, non seulement intéressantes pour les nombres premiers mais aussi pour beaucoup d’autres suites\, sont à l’origine de nombreux problèmes et travaux en théorie des nombres.Dans cet exposé\, nous nous concentrerons sur les chiffres des nombres premiers qui ont suscité beaucoup d’intérêt ces dernières années. Nous explorerons leur pseudo-aléa au travers d’une sélection de résultats récents donnant des estimations du nombre de nombres premiers dont les chiffres vérifient certaines propriétés. \n\n\n\n\n\n\n\nSéminaires des Mathématiques
URL:https://www.math.ens.psl.eu/evenement/pseudo-alea-des-chiffres-des-nombres-premiers/
LOCATION:ENS — amphi Galois\, 45 rue d'Ulm\, Paris\, France
CATEGORIES:ANNÉE 2025-2026,Séminaire Des mathématiques
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260325T110000
DTEND;TZID=Europe/Paris:20260325T120000
DTSTAMP:20260606T010045
CREATED:20260320T100558Z
LAST-MODIFIED:20260320T100559Z
UID:21144-1774436400-1774440000@www.math.ens.psl.eu
SUMMARY:Mingkun Liu\, raconte-moi les surfaces hyperboliques aléatoires !
DESCRIPTION:Après avoir précisé comment tirer au hasard une surface hyperbolique de genre g\, je décrirai la géométrie d’une telle surface aléatoire. En particulier\, on verra que\, lorsque g tend vers l’infini\, sa systole (la longueur de la plus courte géodésique fermée) est en moyenne d’environ 1\,61498.
URL:https://www.math.ens.psl.eu/evenement/mingkun-liu-raconte-moi-les-surfaces-hyperboliques-aleatoires/
LOCATION:Salle W toits du DMA
CATEGORIES:Algèbre et géométrie,Séminaire Raconte-moi
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260323T160000
DTEND;TZID=Europe/Paris:20260323T170000
DTSTAMP:20260606T010045
CREATED:20260320T135208Z
LAST-MODIFIED:20260320T135208Z
UID:21152-1774281600-1774285200@www.math.ens.psl.eu
SUMMARY:Nathan de Montgolfier
DESCRIPTION:Considérons le jeu suivant entre Antigone et Bérénice. Dans un premier temps\, Antigone choisit une loi de probabilités sur les marches aux plus proches voisins sur Z et communique son choix à Bérénice. Antigone choisit également les n premiers pas d’une trajectoire possible selon cette loi et les communique à Bérénice. Le but de Bérénice est alors de deviner la position exacte de la marche à l’instant n+k pour un entier k grand.Si Antigone avait choisi la marche aléatoire simple\, la position au temps n+k s’étalerait sur une fenêtre typique de taille sqrt(k) donnant une probabilité de l’ordre de 1/sqrt(k) à Bérénice de gagner. Mais Antigone peut-elle concevoir une loi beaucoup plus « trompeuse » pour minimiser les chances de Bérénice ?La théorie des chemins imprévisibles\, initiée par Benjamini\, Pemantle et Peres\, et développée par Häggström et Mossel à la fin des années 1990\, apporte une réponse positive à cette question. En choisissant bien la loi\, Antigone peut garantir que la probabilité de succès de Bérénice ne dépasse jamais 1/k^a pour n’importe quel a < 1.Je présenterai une des constructions d’Häggström et Mossel des chemins imprévisibles et une application récente de cette technique à l’étude de transitions de phases de modèles de mécanique statistique sur des réseaux. \n\n\n\n.
URL:https://www.math.ens.psl.eu/evenement/nathan-de-montgolfier/
LOCATION:Salle W
CATEGORIES:Colloquium doctorant
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260320T110000
DTEND;TZID=Europe/Paris:20260320T120000
DTSTAMP:20260606T010045
CREATED:20260312T111117Z
LAST-MODIFIED:20260320T101307Z
UID:21121-1774004400-1774008000@www.math.ens.psl.eu
SUMMARY:Automath! Assia Mahboubi: Computer-assisted mathematics
DESCRIPTION:For more than half a century\, computers have become essential research tools in many areas of fundamental mathematics. They have dramatically expanded the scope of experimentation and visualization\, thereby becoming valuable assistants in the formulation of conjectures. They also play an increasing role in the discovery and verification of proofs. This phenomenon largely predates the rise of AI\, although recent advances in artificial intelligence considerably amplify its impact. This talk will discuss the role of computer tools in contemporary mathematics\, with a particular focus on the potential impact of the rise of interactive theorem proving. \n \nAutomath est un projet collectif pour faire communauté en région parisienne autour de l’informatisation des mathématiques
URL:https://www.math.ens.psl.eu/evenement/automath-assia-mahboubi-computer-assisted-mathematics/
LOCATION:ENS Salle Dussane
CATEGORIES:Séminaire Automath
END:VEVENT
END:VCALENDAR