Generic orbits, normal bases, and generation degree for fields of rational invariants

Abstract: For a linear representation of a finite group in coprime characteristic, we bound the degrees of the invariant polynomials needed to generate the field of rational invariants as a field, in terms of the degrees of the polynomials needed to span the field of rational functions as a vector space over the invariant field. This provides a far-reaching generalization of a recent result of Edidin and Katz.