Elliptic Weyl group elements and unipotent isometries with p=2

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.Comment: 7 page

Bihamiltonian Systems of Hydrodynamic Type and Reciprocal Transformations

We prove that under certain linear reciprocal transformation, an evolutionary PDE of hydrodynamic type that admits a bihamiltonian structure is transformed to a system of the same type which is still bihamiltonian.Comment: 15 page