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Aujourd'hui

ENS-Data Science colloquium – Lénaïc Chizat (EPFL)

Amphi Jaurès (29 Rue d'Ulm)

04 Avril 2024, Lénaïc Chizat (EPFL) Title: A Formula for Feature Learning in Large Neural Networks Abstract: Deep learning succeeds by doing hierarchical feature learning, but tuning hyperparameters such as initialization scales, learning rates, etc., only give indirect control over this behavior. This calls for theoretical tools to predict, measure and control feature learning. In this talk, we will first review various theoretical advances (signal propagation, infinite width dynamics, etc) that have led to a better understanding of the subtle impact of hyperparameters and architectural choices on the training dynamics. We will then introduce […]

Group theory seminar Jaikin-Zapirain/Marquis/Kharlampovich

14:00-17:00 Salle W

April 16 (Tuesday) For this seminar we will have the pleasure of listening to three talks: 14.00 - 14.45 Andrei Jaikin-Zapirain (UAM), "Compressed subgroups in free groups are inert" 15.00 - 15.45 Timothée Marquis (UCL), "Amalgams of rational unipotent groups and residual nilpotence". 16.15 - 17.00 Olga Kharlampovich (CUNY), "Quantification of separability of cubically convex-cocompact subgroups of RAAGs via representations".  Andrei Jaikin-Zapirain  "Compressed subgroups in free groups are inert".   Let F be a free group. A finitely generated subgroup H is called compressed in F if it is not contained […]

CANCELED – Camillo De Lellis – CANCELED

Jussieu -- salle 15-16-309 4 Place Jussieu, Paris, France

Mini-course: Flows of nonsmooth vector fields Consider a vector field v on the Euclidean space. The classical Cauchy-Lipschitz (also named Picard-Lindelöf) Theorem states that, if the vector field is Lipschitz in space, for every initial datum x there is a unique trajectory γ starting at x at time 0 and solving the ODE γ'(t) = v(t, γ(t)). The theorem looses its validity as soon as v is slightly less regular. However, if we bundle all trajectories into a global map allowing x to vary, a celebrated theory started by DiPerna […]

ENS-Data Science colloquium – Michael Jordan

Amphi Jaurès (29 Rue d'Ulm)

Michael Jordan (UC Berkeley and INRIA Paris) Collaborative Learning, Information Asymmetries, and Incentives This colloquium is organized around data sciences in a broad sense, with the goal of bringing together researchers with diverse backgrounds (including mathematics, computer science, physics, chemistry and neuroscience) but a common interest in dealing with complex, large scale, or high dimensional data. More information can be found on the web page of the seminar: https://data-ens.github.io/seminar/

Group theory seminar Tiozzo/Freslon/Bordenave

14:00-17:00 Salle W

An afternoon on random walks on groups. 14.00 - 14.45   Giulio Tiozzo (Toronto) ``Roots of Alexander polynomials of random positive braids'';   15.00 - 15.45   Amaury Freslon (Orsay)  ``How to (badly) shuffle cards?''; 16.15 - 17.00   Charles Bordenave (Marseille) ``Strong convergence of matrix algebras and applications to random walks''.   Giulio Tiozzo  ``Roots of Alexander polynomials of random positive braids'' As originally observed experimentally by Dehornoy, roots of Alexander polynomials of random knots display interesting patterns. In this work, joint with N. Dunfield, we prove several results […]

Systèmes paraboliques à diffusion croisée

Jussieu -- salle 15-16-309 4 Place Jussieu, Paris, France

Résumé du cours : Le système SKT est un système parabolique non linéaire introduit en dynamique des populations à la fin des années '70. Dans cette première partie je présenterai une construction des solutions faibles globales à ce système en me reposant sur la structure d'entropie découverte par Chen et Jüngel en 2006, sa généralisation par Desvillettes et. al. en 2015 et la persistance entropique offerte par certains schémas d'approximation, suivant un travail en collaboration avec Helge Dietert (2022). Nous commencerons par résoudre, à l'aide d'une estimée de dualité, le […]