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  • 5 minutes Lebesgue
    Mar 28, 2017

    Les vidéos des exposés seront mises en ligne quelques jours après l'exposé. Vidéothèque

    Prochain exposé : Rediffusion :

    28-03-2017:  Marc Raynaud La machine de Turing

    Lieu

    Rennes

    Exposés à venir:

    04-04-2017:  Barbara Schapira

    25-04-2017:  Basile Pillet

  • XVI Journées Louis Antoine
    Mar 30, 2017 to Mar 31, 2017

    Statistiques : regret et parcimonie

    Deux mini-cours de 3 heures

    Gilles Stoltz (CNRS, HEC): Bandits stochastiques avec un nombre fini de bras : résultats d'optimalité sur le regret.

    et

    Sara van de Geer (ETH Zürich) :Estimation and testing under sparsity.

    et un exposé complémentaire

    Cyril Lacoste (Université de Rennes 1): Statistiques et sommes de trois carrés.

    Voir le site des JLA

  • School - Flows and Limits in Kähler Geometry
    Apr 18, 2017 to Apr 22, 2017

    Nantes, from April 18th to April 22nd

    Organization board: Sébastien Boucksom, Yann Rollin, Carl Tipler

    Scientific board: Claudio Arezzo, Olivier Biquard, Paul Gauduchon, Michael Singer

    Kähler geometry is a very active research field, at the crossroads between algebraic and Riemannian geometry. Important breakthrough, that lead to solve the Yau-Tian-Donaldson conjecture in the Fano case, have been achieved recently. A spring school involving mini-lectures and talks around this thread of new ideas in Kähler geometry is organized at Nantes University. The goal of the school is to develop certain technical skills, useful to address a variety of important questions in algebraic geometry and global analysis on manifolds, aimed for PhD students and young researchers. Geometric flows, like the Kähler-Ricci flow for instance, and the associated quantification by the Donaldson dynamical system, will be among the essential tools dealt with during the school.

  • Conference - Teichmüller Theory in Higher Dimension and Mirror Symmetry
    Apr 24, 2017 to Apr 28, 2017

    QR-Code

    Angers, from April 24th to April 28th

    Organization board: Frédéric Mangolte, Etienne Mann, Laurent Meersseman, Alexis Roquefeuil

    Teichmüller theory and mirror symmetry are very active domains. In this conference, we propose two series of lectures by two world leader mathematicians :

    • Misha Verbitsky on Teichmüller theory
    • Dimitri Zvonkine, University Pierre et Marie Curie

    Speakers:

    • Gaetan Borot, Max Planck Institut, Bonn
    • Fabrizio Catanese, University of Bayreuth
    • Ekaterina Amerik, University of Orsay (tbc)
    • Maxim Kontsevich, IHES (tbc)
    • Thomas Reichelt, University of Heidelberg
    • Jacopo Stoppa, SISSA
    • Claude Sabbah, Ecole polytechnique
    • Adrien Sauvaget, University Pierre et Marie Curie
    • Andrei Teleman, University of Aix-Marseille
  • Séminaire Quimpériodique
    Jun 1, 2017 to Jun 2, 2017

    Ce séminaire de géométrie, complètement à l'Ouest, réunit à Quimper, trois fois l'an, pour deux journées, le jeudi et le vendredi, des géomètres venus des régions Bretagne et Pays de Loire.

    Programme

    Inas Amacha (LMBA): TBA;
    Vincent Colin (LMJL): TBA;
    Bertrand Deroin (ENS Paris): TBA;
    Victor Kleptsyn (IRMAR): TBA;
    Paul Laurain (univ. Paris VII): TBA.

    Correspondants

    Guillaume Deschamps, LMBA, Brest
    Laurent Meersseman, LAREMA, Angers
    Gaël Meigniez, LMBA, Vannes
    Yann Rollin, LMJL, Nantes
    Frédéric Touzet, IRMAR, Rennes

    Historique

    Historique du séminaire

    Affiche

    Télecharger l'affiche ici

  • Conference - Infinite measure Dynamics
    Jun 6, 2017 to Jun 9, 2017

    Brest, from June 6th to June 9th

    Organization board: Yves Coudène, François Maucourant, Françoise Pène, Barbara Schapira, Samuel Tapie, Annick Nicolle

    Scientific board: Jon Aaronson, Jean-Pierre Conze, Gilles Courtois, Domokos Szasz

    This conference will focus on dynamical systems which naturally preserve a measure with infinite mass. These systems appear in a geometric or probabilistic context, or may come from natural sciences. When the invariant measure has infinite mass, recurrence is no longer automatic, usual mixing properties disappear and new asymptotical properties (such as rationnal ergodicity) may occur. Such systems may develop various and subtil behaviours, which could not exists in finite measure dynamics.

    This conference will gather international experts on this topic, and will allow young researcher to have an easy access to the large recent developpment on such questions.

  • Conference - Families of algebraic dynamical systems
    Jun 12, 2017 to Jun 16, 2017

    Rennes, from June 12th to June 16th

    Organization board: Serge Cantat, Christophe Dupont

    Scientific board: Matthew Baker, Eric Bedford, Serge Cantat, Christophe Dupont, Mattias Jonsson

  • Conference - Random walks on algebraic structures-On honour of Yves Guivarc'h
    Jun 19, 2017 to Jun 23, 2017

    Rennes, from June 19th to June 23rd

    Organization board: Bachir Bekka, Nizar Demni

    Scientific board: Bachir Bekka, Emmanuel Breuillard, Nizar Demni, Alex Lubotzky

    The conference deals with themes around random walks on algebraic structures. Dynamical sytems on groups, homogeneous spaces, and related structures (graphs, quantum groups , groupoids,...) are rich objects, involving various fields of mathematics (probability, group theory, topology, number theory, operator algebras, Banach space geometry, etc). They are also useful as modelling tools for other sciences (physics, computer science, economics, etc); for instance, expander graphs, which are of interest in theoretical computer science, are graphs for which the associated random walk has special spectral properties and their explicit construction involves sophisticated tools such as Kazhdan's property (T) or Selberg's inequality. The conference aims to give a flavor of the various aspects of the subject by bringing together some experts with major contributions to the field. This conference will also be the opportunity to celebrate the 80th birthday of Yves Guivarc'h, who played a major part in the development of probability on algebraic and geometric structures, a subject with an ever growing interest for the last 30 years.

Conference - Loop spaces in geometry and topology

Nantes, from Sept 1st to 5th, 2014
Contact: H. Abbaspour
Organisation board: H. Abbaspour (Nantes), A. Oancea (Paris), N. Wahl (Copenhagen)

One-dimensional objects have played a central role in geometry for a long time. From lines in Euclidean spaces to geodesics in Riemannian manifolds, particular classes of real one-dimensional sub-objects of a given space, i.e. loops or paths, have been successfully used as probes for the ambient geometry. At the local level, Riemannian curvature can be classically recovered from the behavior of geodesic paths via the Jacobi equation. At the global level, landmark results such as Morse's development of the calculus of variations in the large (1929), Berger's classification of holonomy groups (1953), Gromoll and Meyer's homological criterion for the existence of infinitely many closed geodesics (1969), or its reinterpretation by Sullivan-Vigué from the viewpoint of rational homotopy theory (1976), have shown deep connections between spaces of loops and analysis, Lie group theory, or topology. From a quite different perspective, string theory considers loops and paths (strings), as well as Riemann surfaces (worldsheets), as the basic building blocks for a unified theory of matter.

On the mathematical side, symplectic geometry appears to be the most natural setup within which real 1-dimensional objects (loops/paths) interact with complex 1-dimensional objects (Riemann surfaces). Gromov's theory of pseudo-holomorphic curves (1985) and its reinterpretation by Floer as a variational theory for the unregularized gradient flow of the symplectic action functional (1987) proved to be a successful tool in order to address the Arnold and Weinstein conjectures (1986, 1979) on the existence of closed orbits/chords for Hamiltonian systems. The geometric structure of compactified moduli space of pseudo-holomorphic curves gives rise to sophisticated algebraic structures, and in particular to various homology theories such as Floer homology, (embedded) contact homology, Seiberg-Witten-Floer homology, ... In all of these theories, one introduces higher products that account for all the non-canonical choices that one needs to make in order to lift an associative product from homology to the chain level. These operations get organized into a differential which is a coderivation on a larger object known to algebraic topologists as the “Bar construction”.

Almost simultaneously and inspired by the algebraic structures encountered in quantum field theory, algebraic topologists have been trying to understand the chain complexes of free loop and path spaces of a manifold. Chas and Sullivan's natural idea of cutting and pasting loops/paths together with considering Poincaré duality for the underlying manifold has led to a plethora of operations and opened a new field known as “string topology”. In parallel to this topological approach, a lot of effort was put into understanding the algebraic structure of “algebraic loop spaces”, modeled as Hochschild complexes of DGAs or categories equipped with further structures that account for Poincaré duality in the topological setting.

The various procedures for assigning a linear object (complex, homology, category...) to a nonlinear object gave rise to rich homotopical structures. There are many striking (algebraic) similarities between the constructions and difficulties encountered in each of the previous three settings. The common desire to reorganize non-canonical choices into higher homotopies and categories has also led to more elegant formulations of geometric and topological statements in terms of derived categories and functors.

We think that the time is ripe to bring together experts and young mathematicians working in these areas. We expect fruitful interactions and hope to harvest inspiration and new ideas. To this end, we intend to have 5 mini-courses accessible to non-experts, followed by a few talks dealing with more recent developments.

Partners

Irmar LMJL ENS Rennes LMBA LAREMA

Affiliation

ANR CNRS Rennes 1 Rennes 2 Nantes INSA Rennes INRIA ENSRennes UBO UBS Angers UBL