Séminaire de Géométrie Arithmétique Paris-Pékin-Tokyo

Deformation and rigidity of $\ell$-adic sheaves

by Prof. Lei FU (Tsinghua University)

Centre de conférences Marilyn et James Simons (IHES)

Centre de conférences Marilyn et James Simons


Le Bois Marie 35, route de Chartres 91440 Bures-sur-Yvette

Let X be a smooth connected algebraic curve over an algebraically closed field, let S be a finite closed subset in X, and let F_0 be a lisse l-torsion sheaf on X-S. We study the deformation of F_0. The universal deformation space is a formal scheme. Its generic fiber has a rigid analytic space structure. By studying this rigid analytic space, we prove a conjecture of Katz which says that if a lisse $\overline{Q}_\ell$-sheaf F is irreducible and physically rigid, then it is cohomologically rigid in the sense that \chi(X,j_*End(F))=2, where j:X-S--> X is the open immersion.