On separating fixed points from zero by invariants

Abstract

Assume a fixed point v in a G-module V can be separated from zero by a homogeneous invariant of degree dp^r where p>0 is the characteristic of the ground field k and p, d are coprime. We show that then v can also be separated from zero by an invariant of degree p^r , which we obtain explicitly from f. It follows that the minimal degree of a homogeneous invariant separating v from zero is a p-power.