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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

    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.

School - Flows and Limits in Kähler Geometry

List of (confirmed) speakers

Mini-courses :

Talks :

Titles and abstracts

  • Bo Berndtsson (Chalmers University) : Direct image bundles and variations of complex structures

Given a smooth proper fibration $p:\mathcal X\to B$ and $L$ a line bundle over $\mathcal X$, the direct image $$ E:= p_*(L) $$ is in many cases a holomorphic vector bundle over $B$. Its fibers are the spaces of holomorphic sections of $L$ over the fibers of $p$, $X_t=p^{-1}(t)$, and they can be given various $L^2$-metrics. In case the fibration is of relative dimension $n$ so that the fibers are compact Riemann surfaces, special cases of this situation can be used to study the variation of complex structures on the fibers $X_t$. (The fibers are all diffeomorphic, but their complex structure varies with $t$, so we can view the family $X_t$ as a family of variations of complex structures on one fixed smooth manifold.) When the relative dimension is higher than one the situation is more complicated and one needs to consider also higher direct images. I will discuss the problems that arise in this connection, with previous work of Siu, Schumacher and To-Yeung and some recent joint work with Xu Wang and Mihai Paun.

  • Hans-Joachim Hein (Fordham University) : Tangent cones of Calabi-Yau varieties

It has been known for about 10 years that the classical Calabi-Yau theorem on the existence and uniqueness of Ricci-flat Kahler metrics on smooth complex manifolds with zero first Chern class can be extended to a natural setting of weak Kahler metrics on singular complex varieties. However, until relatively recently nothing was known - even in the simplest nontrivial examples - about the precise asymptotic behavior of these weak Ricci-flat metrics at the singularities of the underlying varieties. I will explain work of Donaldson-Sun, H-Naber and H-Sun that resolves this question in certain cases.

  • Valentino Tosatti (Northwestern University) : Metric Limits of Calabi-Yau Manifolds

In this mini-course I will give an introduction to the study of limits of Ricci-flat Kahler metrics on a compact Calabi-Yau manifold when the Kahler class degenerates to the boundary of the Kahler cone. Analytically, the problem is to prove suitable uniform a priori estimates for solutions of a degenerating family complex Monge-Ampère equations, away from some singular set. Geometrically, this can be used to understand the Gromov-Hausdorff limit of these metrics. And if the manifold is projective algebraic and the limiting class is rational, the limits possess an algebraic structure and are obtained from the initial manifold via contraction morphisms from Mori theory.

  • Jeff Viaclovsky (Wisconsin University) : The geometry of SFK ALE metrics

I will discuss some of the basics of scalar-flat Kaehler (SFK) metrics, and focus on the geometry of SFK metrics which are asymptotically locally Euclidean (ALE). These space arise as "bubbles" in the compactness theory of Calabi's extremal Kaehler metrics. I will also present some of the deformation theory of SFK ALE metrics.

  • Thibaut Delcroix (ENS Paris) : Kähler geometry of horospherical manifolds

Horospherical manifolds form a class of almost homogeneous manifolds whose Kähler geometry is very close to that of toric manifolds. They strictly contain homogeneous toric bundles, to which a lot of results holding for toric manifolds have been extended. I will present horospherical manifolds, trying to convince you that they are not much harder to deal with, and in particular I will present the criterion for K-stability in the Fano case that follows either from my work on spherical varieties, or from a direct, Wang-Zhu type, approach.

  • Eleonora Di Nezza (Imperial College) : Monge-Ampère energy and weak geodesic rays

The recent proof of Demailly's conjecture by Witt Nyström gives another evidence that pluripotential theory play a key role when working with complex Monge-Ampère equations in order to solve problems in differential and algebraic geometry. In this talk we investigate pluripotential tools: we characterise Monge-Ampère energy classes in terms of envelopes. And in order to do that, we develop the theory of weak geodesic rays in a big cohomogy class. We also give a positive answer to an open problem in pluripotential theory. This is a joint work with Tamas Darvas and Chinh Lu.

  • Jakob Hultgren (Chalmers University) : Coupled Kähler-Einstein Metrics

A central theme in complex geometry is to study various types of canonical metrics, for example Kähler-Einstein metrics and cscK metrics. In this talk we will introduce the notion of coupled Kähler-Einstein (cKE) metrics which are k-tuples of Kähler metrics that satisfy certain coupled Kähler-Einstein equations. We will discuss existence and uniqueness properties and elaborate on related algebraic stability conditions. (Joint work with David Witt Nyström)

  • Zakarias Sjostrom Dyrefelt (Université de Toulouse) : TBA

Partners

Irmar LMJL ENS Rennes LMBA LAREMA

Affiliation

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