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  • New numerical schemes for extreme geophysical phenomena
    Sep 29, 2016 to Sep 30, 2016

    Final GeoNum Workshop

    New numerical schemes for extreme geophysical phenomena

    The GeoNum project aims at deriving high-order numerical methods to approximate nonlinear hyperbolic systems that arise when considering gravitational flows. The objectives are twofold. On the one hand, relevant models have to be carefully chosen in order to perform simulations of physical interest. Indeed, geophysical flows are generally modelled using Saint-Venant equations, which are not systematically well adapted to predict sophisticated shallow water flows. These models have to be extended to take into account important phenomena including turbulence, complex bathymetries or the sediments' impact on the topography's variation. On the other hand, the developments of new strategies to enforce highly accurate approximations required to simulate environmental flows are considered. Moreover, a particular attention must be paid on the robustness of the suggested algorithms. To address such an issue, classical schemes have to be extended into relevant high order approximations independently of both chosen topography and domain geometry. As a consequence, the resulting approaches are well adapted to perform real-life simulations.

    Lieu: Laboratoire de Mathématiques Jean Leray

    website of the conference

  • 5 minutes Lebesgue
    Sep 29, 2016

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

    Prochain exposé:

    29-09-2016:  Frédéric Hélein
    Le paysage actuel de l'édition scientifique

    Lieu

    Irmar, Salles 004-006, 09h00

    Exposés à venir:

    07-10-2016:  Thomas Wallez
    21-10-2016:  Joe Viola
    18-11-2016:  Guillem Cazasus
    01-12-2016:  Didier Robart

  • Journée d'information et de réflexion sur l'édition scientifique
    Sep 29, 2016

    Cette journée a pour objectif d'informer les mathématicien-ne-s rennais-es sur le paysage de l'édition scientifique mathématique actuel et ses évolutions en cours. Elle ambitionne également de stimuler des comportements vertueux des individus et des structures en matière de publication d'articles et d'utilisation des ressources documentaires.

    Programme

    09:30-10:30 Frédéric Hélein, Le paysage actuel de l'édition scientifique
    10:30-11:30 Thierry Bouche, Présentation du Cedram et autres nouvelles initiatives
    11:30-12:30 Laurent Guillopé, La SMF comme maison d'édition
    12:30-14:00 Déjeuner
    14:00-15:00 Reinie Erné et Bas Edixhoven, La Fondation Compositio Mathematica
    15:00-16:00 Claude Sabbah, Un exemple de journal électronique, le Journal de l'Ecole Polytechnique
    16:00-16:30 Benoît Claudon, ÉPIGA : retour d'expérience sur son lancement

    Organisateurs

    Maryse Collin, Matthieu Romagny (organisateurs principaux), Xavier Caruso, Françoise Dal'Bo, Michel Gros, Frank Loray, Florian Méhats, Christophe Mourougane, Nicolas Raymond, San Vũ Ngọc

    Lieu

    Tous les exposés ont lieu dans la salle 004-006, au rez-de-chaussée de l'IRMAR.

  • Conference - Lebesgue PhD meeting 2016
    Oct 19, 2016 to Oct 21, 2016

    Angers, from October 19th to October 21st

    Organization board: Clément du Crest de Villeneuve, Clément Fromenteau, Guillaume Roux, Johan Leray

    Scientific board: Viet Anh Nguyen, Olivier Thom, Caroline Vernier

  • XV Journées Louis Antoine
    Nov 3, 2016 to Nov 4, 2016

    Théorie du Contrôle

    Deux mini-cours de 3 heures

    Franck Boyer (Université Paul Sabatier - Toulouse) : Contrôlabilité des systèmes paraboliques linéaires et de leurs discrétisations.

    et

    Jean-Michel Coron (Université Pierre et Marie Curie) :Contrôle de systèmes et non linéarités.

    et un exposé complémentaire

    Néstor Fernàndez Vargas (Université de Rennes1) :Difféomorphismes, transitivité et densité.

    Voir le site des JLA

  • Conference - CAST - Contact and Symplectic Topology
    Jan 26, 2017 to Jan 28, 2017

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    Nantes, from January 26th to January 28th

    Organization board: Baptiste Chantraine, Vincent Colin, Paolo Ghiggini

    Scientific board: Jean-François Barraud, Baptiste Chantraine, Kai Cieliebak, Tobias Ekholm

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

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    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

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    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
    • Amerik Ekaterina, University of Orsay (tbc)
    • Maxim Kontsevich, IHES (tbc)
    • Thomas Reichelt, University of Heidelberg
    • Jacopo Stoppa, SISSA
    • Claude Sabbah, Ecole polytechnique
    • Andrei Teleman, University of Aix-Marseille

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

Affiliation

ANR CNRS Rennes 1 Rennes 2 Nantes INSA Rennes INRIA ENSRennes UBL