Rencontre BordeauxPoitiers
7/8 octobre 2021, Bordeaux, France
jeudi, 7 octobre

11h3012h20 
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) 


15h3016h45 
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
Orateurs
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 ADE singularities. The proof of this fact avoid as much as possible a casebycase 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 ominimal geometry
Abstract : In this lectures I will introduce ominimal 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 M_{20}
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 M_{20}. In this talk, we are interested in projective K3 surfaces admitting a faithful symplectic action of the group M_{20}. 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 M_{20}.
Chuyu Zhou (Lausanne)
Title : Effective semiampleness of Hodge bundles on curves
Abstract : In this talk, we will explain how to apply the rencent progress on Kmoduli to obtain effective semiampleness of Hodge line bundles for some special families, more precisely, for QGorenstein klttrivial fibration whose fibers are klt CalabiYau 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