Dan Abramovich

Tame stacks and reduction of coverings

Abstract: This is joint work with Martin Olsson and Angelo Vistoli, in which we describe a class of algebraic stacks, called tame stacks, which for many purposes is a good replacement for Deligne-Mumford stacks in finite and mixed characteristics. This is based on a classification of finite flat linearly reductive group schemes, which should be of independent interest if indeed it is not yet known (a fact that seems correct yet hard to believe).