proposition: Lemma astab1J x : 'C[x |'J] = 'C[x].
proof: Proof. by rewrite astabJ cent_set1. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)