Section ModularRepresentation.
Variables (F : fieldType) (p : nat) (gT : finGroupType).
Hypothesis charFp : p \in [char F].
Implicit Types G H : {group gT}.

(* This is Gorenstein, Lemma 2.6.3. *)
Lemma rfix_pgroup_char G H n (rG : mx_representation F G n) :
n > 0 -> p.-group H -> H \subset G -> rfix_mx rG H != 0.