proposition: Lemma rker_conj : rker rGB = rker rG.
proof: Proof. apply/setP=> x; rewrite !inE /= mulmxA (can2_eq (mulmxKV uB) (mulmxK uB)). by rewrite mul1mx -scalar_mxC (inj_eq (can_inj (mulKmx uB))) mul1mx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div choice fintype tuple finfun bigop prime) mathcomp(ssralg poly polydiv finset fingroup morphism) mathcomp(perm automorphism quotient finalg action zmodp) mathcomp(commutator cyclic center pgroup matrix mxalgebra) mathcomp(mxpoly)