Subextensions for a permutation PSL(2,q)-module

Abstract

Using cohomological methods, we prove the existence of a subgroup isomorphic to SL(2,q), q = -1 (mod 4), in the permutation module for PSL(2,q) in characteristic 2 that arises from the action on the projective line. A similar problem for q = 1 (mod 4) is reduced to the determination of certain first cohomology groups.