Journal of Algebra and its Applications, 2025 (SCI-Expanded)
In this paper, we study n-MacWilliams right R-modules. It is shown that (1) the MacWilliams extension property for n = 1 implies that MR is an automorphism-invariant module (the converse holds if MR is finitely cogenerated), (2) for n = 2, the MacWilliams extension property implies that MR is quasi-injective which yields that if the matrix ring Mn(R) over a right finitely cogenerated ring R is right 1-MacWilliams, then R is also right 1-MacWilliams. We also show that (3) a right automorphism-invariant ring containing no infinite orthogonal sets of idempotents with essential right socle is right pseudo-Frobenius and (4) if R is a right 1-MacWilliams ring and it has ACC on right annihilators, then R is quasi-Frobenius which generalize answers the question of when is a MacWilliams ring quasi-Frobenius and when is a quasi-Frobenius ring a right artinian, right automorphism-invariant?