Elliptic Weyl group elements and unipotent isometries with p=2

Abstract

Let G be a classical group over an algebraically closed field of characteristic 2 and let C be an elliptic conjugacy class in the Weyl group. In a previous paper the first named author associated to C a unipotent conjugacy class \Phi(C) in G. In this paper we show that \Phi(C) can be characterized in terms of the closure relations between unipotent classes. Previously the analogous result was known in odd characteristic and for exceptional groups in any characteristic.