proposition: Lemma mcoeffXU (i j : 'I_n) : ('X_i @_U_(j) : R) = (i == j)%:R.
proof: Proof. by rewrite mcoeffX eq_mnm1. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(ssralg ssrint fingroup perm) mathcomp(ssrcomplements freeg mpoly) sorted tools ordtype permuted partition skewpart composition Yamanouchi std tableau stdtab skewtab permcent antisym Schur_mpoly therule Schur_altdef unitriginv