Rencontre Bordeaux-Poitiers

7/8 octobre 2021, Bordeaux, France


jeudi, 7 octobre
11h30-12h20 Alessandra Sarti (Université de Poitiers)
14h - 15h15 Yohan Brunebarbe (Université de Bordeaux)
15h45 - 16h35 Romain Demelle (Université de Poitiers)
vendredi, 8 octobre
10h00 - 10h50 Chuyu Zhou (Ecole Polytechnique Lausanne)

11h20 - 12h10 Alessandra Sarti (Université de Poitiers)
15h30-16h45 Yohan Brunebarbe (Université de Bordeaux)

Les exposés seront à l'Institut de Mathématiques de Bordeaux UMR 5251 Université de Bordeaux 351, cours de la Libération - F 33 405 TALENCE

Organisateurs : Enrica Floris, Andrea Fanelli


Alessandra Sarti (Poitiers)

Title : Complex Reflection Groups and K3 surfaces

Abstract : In these lectures I will show a classification of all K3 surfaces that one can obtain as quotient of surfaces by certain subgroups of finite complex reflection groups of rank 4. Most of these K3 surfaces are singular with A-D-E singularities. The proof of this fact avoid as much as possible a case-by-case analysis and involves the theory of finite complex reflection groups. Moreover I will show that each family contains K3 surfaces with the maximum Picard number which is 20. This construction generalizes a previous result by W. Barth and myself and is based on a series of papers in collaboration with C. Bonnafé.

Yohan Brunebarbe (Bordeaux)

Title : Algebraicity of period maps via o-minimal geometry

Abstract : In this lectures I will introduce o-minimal geometry and illustrate its relevance to proving algebraicity of certain analytically defined objects. As an application, I will explain that the period maps associated to variations of pure Hodge structures are algebraic in corestriction to their image, as conjectured by Griffiths. This is based on joint work with Benjamin Bakker and Jacob Tsimerman.

Romain Demelle (Poitiers)

Title : K3 surfaces with action of the Mathieu group M20

Abstract : It was shown by Mukai that the maximum order of a finite group acting faithfully and symplectically on a K3 surface is 960 and if such a group has order 960, then it is isomorphic to the Mathieu group M20. In this talk, we are interested in projective K3 surfaces admitting a faithful symplectic action of the group M20. The aim will be to describe all of them and to understand when it is possible to construct explicit projective models for these surfaces. We will also see that it exists an infinite number of K3 surfaces admitting such an action of M20.

Chuyu Zhou (Lausanne)

Title : Effective semi-ampleness of Hodge bundles on curves

Abstract : In this talk, we will explain how to apply the rencent progress on K-moduli to obtain effective semi-ampleness of Hodge line bundles for some special families, more precisely, for Q-Gorenstein klt-trivial fibration whose fibers are klt Calabi-Yau pairs of Fano type.

Cette rencontre est soutenue par un Projet Exploratoire Premier Soutien, la Fédération MARGAUx, le projet ANR Fibalga et l'Université de Bordeaux