Section ExtraspecialFormspace.
Variable G : {group gT}.
Hypotheses (pG : p.-group G) (esG : extraspecial G).
Let p_pr := extraspecial_prime pG esG.
Let oZ := card_center_extraspecial pG esG.
Let p_gt1 := prime_gt1 p_pr.
Let p_gt0 := prime_gt0 p_pr.

(* This is the tranposition of the hyperplane dimension theorem (Aschbacher   *)
(* (19.1)) to subgroups of an extraspecial group.                             *)
Lemma subcent1_extraspecial_maximal U x :
U \subset G -> x \in G :\: 'C(U) -> maximal 'C_U[x] U.