Institut de Mathématiques de Marseille, UMR 7373


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24 novembre 2017: 3 événements


  • Groupe de Travail Guide d’ondes, milieux stratifiés et problèmes inverses (GOMS)

    Du 23 novembre 14:00 au 24 novembre 18:00 - Inverse problems and related fields 17 (IP&RF17)

    Groupe de Travail Guide d’ondes, milieux stratifiés et problèmes inverses (GOMS)

    Notes de dernières minutes : Toutes les informations relatives à ce workshop IP&RF17 sont accessibles en ligne à l’adresse :

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    En savoir plus : Groupe de Travail Guide d’ondes, milieux stratifiés et problèmes inverses (GOMS)

  • Séminaire Signal et Apprentissage

    Vendredi 24 novembre 10:00-11:00 - Minh HA QUANG - IIT, Genoa

    Covariance matrices and covariance operators in machine learning and pattern recognition : A geometrical framework

    Résumé : Symmetric positive definite (SPD) matrices, in particular covariance matrices, play important roles in many areas of mathematics and statistics, with numerous applications in various different fields, including machine learning, brain imaging, and computer vision. The set of SPD matrices is not a subspace of Euclidean space and consequently algorithms utilizing only the Euclidean metric tend to be suboptimal in practice. A lot of recent research has therefore focused on exploiting the intrinsic geometrical structures of SPD matrices, in particular the view of this set as a Riemannian manifold. In this talk, we will present a survey of some of the recent developments in the generalization of finite-dimensional covariance matrices to infinite-dimensional covariance operators via kernel methods, along with the corresponding geometrical structures. This direction exploits the power of kernel methods from machine learning in the framework of Riemannian geometry, both mathematically and algorithmically. The theoretical formulation will be illustrated with applications in computer vision, which demonstrate both the power of kernel covariance operators as well as of the algorithms based on their intrinsic geometry.

    JPEG - 34.6 ko
    Minh HA QUANG

    Lieu : CMI, salle de séminaire R164 (1er étage) - I2M - Château-Gombert
    39 rue Frédéric Joliot-Curie
    13453 Marseille cedex 13

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    En savoir plus : Séminaire Signal et Apprentissage

  • Séminaire Teich

    Vendredi 24 novembre 11:00-12:00 - Rodolfo GUTIÉRREZ-ROMO - IMJ-PRG, Paris 7

    Rauzy-Veech groups of flat surfaces

    Résumé : The Rauzy–Veech induction is a powerful renormalization procedure for (half-)translation flows. By tracking the changes it induces in homology, we define the Rauzy–Veech monoid (or group) of a connected component of a stratum of Abelian or quadratic differentials. This monoid was proven to be pinching and twisting by Avila and Viana, which implies the Kontsevich–Zorich conjecture stating the simplicity of the Lyapunov spectrum of almost every translation flow with respect to the Masur–Veech measures.
    In this talk, I will present a full classification of the Rauzy–Veech groups of Abelian strata : they are explicit finite-index subgroups of their ambient symplectic groups. This is strictly stronger than pinching and twisting. Moreover, some techniques can be extended to the quadratic case to prove that the indices of the Rauzy–Veech groups of certain connected components of quadratic strata are also finite. This proves that the “plus” Lyapunov spectra of such strata is simple, which was not previously known.

    JPEG - 35.1 ko

    Lieu : FRUMAM - Aix-Marseille Université - Site St Charles
    3, place Victor Hugo - case 39
    13331 MARSEILLE Cedex 03

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    En savoir plus : Séminaire Teich

24 novembre 2017: 1 événement

groupe de travail

  • Agenda ERC IChaos

    Du 10 novembre au 2 décembre - Alexander Bufetov

    Scientific collaboration with Andrey Dymov

    Résumé : to continue the work on the infinite dimensional stochastic differential equations

    Lieu : Stecklov Math. Institute - Moscow

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En savoir plus : Agenda ERC IChaos

24 novembre 2017: 2 événements

Manifestation scientifique