A resolution of singularities for Drinfeld’s compactification by stable maps

Abstract

Drinfeld’s relative compactification plays a basic role in the theory of automorphic sheaves, and its singularities encode representation-theoretic information in the form of intersection cohomology. We introduce a resolution of singularities consisting of stable maps from nodal deformations of the curve into twisted flag varieties. As an application, we prove that the twisted intersection cohomology sheaf on Drinfeld’s compactification is universally locally acyclic over the moduli stack of G G -bundles at points sufficiently antidominant relative to their defect.