The pointed p-groups on a block algebra

Abstract

A pointed p-group is a pointed group P gamma such that Pis a p-group. We parameterize the pointed p-groups on a group algebra or on a block algebra of a group algebra. This is equivalent to a parameterization of the isomorphism classes of indecomposable direct summands of the algebra as a bimodule with the group acting on the left and a p-subgroup acting on the right. The parameterization involves p-subgroups and irreducible characters of centralizers of p-subgroups.