Section CentMxDef.
Variables (m n : nat) (R : 'A[F]_(m, n)).
Definition cent_mx_fun (B : 'M[F]_n) := R *m lin_mx (mulmxr B \- mulmx B).
Canonical cent_mx_fun_additive := Additive cent_mx_fun_is_linear.
Canonical cent_mx_fun_linear := Linear cent_mx_fun_is_linear.
Definition cent_mx := kermx (lin_mx cent_mx_fun).
Definition center_mx := (R :&: cent_mx)%MS.
End CentMxDef.
Local Notation "''C' ( R )" := (cent_mx R) : matrix_set_scope.
Local Notation "''Z' ( R )" := (center_mx R) : matrix_set_scope.

Lemma cent_rowP m n B (R : 'A_(m, n)) :
reflect (forall i (A := vec_mx (row i R)), A *m B = B *m A) (B \in 'C(R))%MS.