2002/01/31 by Manuel Blickle
Mathematics · #math.AG #math.AC #msc:13A35 #msc:16S99
published as Trans. Am. Math. Soc 355 (2003), 4, 1647-1668 · 25 pages. Some minor changes following referee's suggestion. To appear in Trans. AMS
arxiv created 2003/06/06 · arxiv updated 2009/11/30
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.