proposition: Fact vchar_mulr_closed : mulr_closed 'Z[irr G].
proof: Proof. split; first exact: cfun1_vchar. move=> _ _ /vcharP[xi1 Nxi1 [xi2 Nxi2 ->]] /vcharP[xi3 Nxi3 [xi4 Nxi4 ->]]. by rewrite mulrBl !mulrBr !(rpredB, rpredD) // char_vchar ?rpredM. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div choice fintype tuple finfun bigop prime order) mathcomp(ssralg poly finset fingroup morphism perm) mathcomp(automorphism quotient finalg action gproduct) mathcomp(zmodp commutator cyclic center pgroup sylow) mathcomp(frobenius vector ssrnum ssrint archimedean intdiv) mathcomp(algC algnum classfun character integral_char)