The D-Module structure of R[F]-modules
Abstract
Description
Let R be a regular ring essentially of finite type over a perfect field k. An R-module M is called a unit R[F]-module if it comes equipped with an isomorphism F*M-->M where F denotes the Frobenius map on Spec R, and F* is the associated pullback functor. It is well known that M then carries a natural D-module structure. In this paper we investigate the relation between the unit R[F]-structure and the induced D-structure on M. In particular, it is shown that, if k is algebraically closed and M is a simple finitely generated unit R[F]-module, then it is also simple as a D-module. An example showing the necessity of k being algebraically closed is also given.
25 pages. Some minor changes following referee's suggestion. To appear in Trans. AMS
25 pages. Some minor changes following referee's suggestion. To appear in Trans. AMS