Automorphisms of Chevalley groups of types A l , D l , or E l over local rings with 1/2

Abstract

In this paper, we prove that every automorphism of an (elementary) Chevalley group of type A l , D l , or E l , l ≥ 2, over a commutative local ring with 1/2 is standard, i.e., is the composition of inner, ring, graph, and central automorphisms.