Let K be a field and Ο an automorphism of K of order n. We study
the eigenspace of a bounded skew polynomial fβK[t;Ο], with emphasis
on the case of a cyclic field extension K/F of degree n, where Ο
generates the Galois group. We obtain lower bounds on its dimension, and
compute it in special cases.Comment: Rewritten and streamlined new version, some results are improve