Contramodules for algebraic groups: induction and projective covers

Abstract

In this paper we will investigate contramodules for algebraic groups. Namely, we give contra-analogs to two 20th century results about comodules. Firstly, we show that induction of contramodules over coordinate rings of algebraic groups is exact if and only if the associated quotient variety is affine. Secondly, we give an inverse limit theorem for constructing projective covers of simple $G$-modules using $G$-structures of projective covers of simple modules for the first Frobenius kernel, $G_1$.