On Indecomposable and Imprimitive Modules for Finite Groups - A G-Algebra Approach

One of the most useful results in modular representation theoryof finite groups is Green's indecomposability theorem 4]. Inorder to state it in a simple form, let us fix a complete discretevaluation ring O of characteristic 0 with algebraically closedresidue field F of characteristic p0. Unless stated otherwise,all our modules will be free of finite rank over O or F, respectively.In its most popular form, Green's theorem says the following.