Finite generation of Tate cohomology of symmetric Hopf algebras

Abstract

Let $A$ be a finite dimensional symmetric Hopf algebra over a field $k$. We show that there are $A$-modules whose Tate cohomology is not finitely generated over the Tate cohomology ring of $A$. However, we also construct $A$-modules which have finitely generated Tate cohomology. It turns out that if a module in a connected component of the stable Auslander-Reiten quiver associated to $A$ has finitely generated Tate cohomology, then so does every module in that component. We apply some of these finite generation results on Tate cohomology to an algebra defined by Radford and to the restricted universal enveloping algebra of $sl_2(k)$.Comment: 12 pages, comments and suggestions are welcome. arXiv admin note: substantial text overlap with arXiv:0804.4246 by other author