**MSC:**- 20C20 Modular representations and characters
- 16G70 Auslander-Reiten sequences (almost split sequences) and Auslander-Reiten quivers

certain type of non--split short exact sequence of modules over artin

algebras (the definition is repeated here

in (19) below). Since then, this concept has been extensively used in the general

representation theory of finite dimensional algebras, but also --- for example by Erdmann

[2] --- in the much more restricted case of group algebras. In this situation, the most

basic property of Auslander--Reiten sequences, namely their existence, turns out to be

closely related to an old acquaintance, the so called projective maps. The purpose of

the present note is to exhibit this relation, thereby giving a rather explicit construction

of Auslander--Reiten sequences for group algebras. In fact, the construction can be

relativized up to a point (Theorem 17). The reader not interested in this

can always

take $ H = 1 $ in what follows. For another treatment of the topic, see

Greens paper [3].