Section ModularGroupAction.
Variables (aT rT : finGroupType) (D : {group aT}) (R : {group rT}).
Variables (to : groupAction D R) (p : nat).
Implicit Types (G H : {group aT}) (M : {group rT}).

Lemma pcore_sub_astab_irr G M :
p.-group M -> M \subset R -> acts_irreducibly G M to ->
'O_p(G) \subset 'C_G(M | to).