End AbelianQuotient.
Section Similarity.
Variables (gT : finGroupType) (G : {group gT}).
Local Notation reprG := (mx_representation F G).
Variant mx_rsim n1 (rG1 : reprG n1) n2 (rG2 : reprG n2) : Prop :=
MxReprSim B of n1 = n2 & row_free B
& forall x, x \in G -> rG1 x *m B = B *m rG2 x.

Lemma mx_rsim_iso n (rG : reprG n) (U V : 'M_n)
(modU : mxmodule rG U) (modV : mxmodule rG V) :
mx_rsim (submod_repr modU) (submod_repr modV) <-> mx_iso rG U V.