### Representations of finite groups over self-injective rings

## Abstract

For a group algebra over a self-injective ring

there are two stable categories: the usual one modulo projectives

and a relative one where one works modulo representations

which are free over the coefficient ring.

I'll describe the connection between these two stable categories,

which are "birational" in an appropriate sense.

I'll then make some comments on the specific case

where the coefficient ring is Z/nZ and give a more

precise description of the relative stable category.