On the automorphism-invariance of finitely generated ideals and formal matrix rings


Le Van Thuyet, Truong Cong Quynh




In this paper, we study rings having the property that every finitely generated right ideal is automorphism-invariant. Such rings are called right f a-rings. It is shown that a right f a-ring with finite Goldie dimension is a direct sum of a semisimple artinian ring and a basic semiperfect ring. Assume that R is a right f a-ring with finite Goldie dimension such that every minimal right ideal is a right annihilator, its right socle is essential in R R, R is also indecomposable (as a ring), not simple, and R has no trivial idempotents. Then R is QF. In this case, QF-rings are the same as q−, f q−, a−, f a-rings. We also obtain that a right module (X, Y, f,) over a formal matrix ring R M N S with canonical isomorphisms f and g is automorphism-invariant if and only if X is an automorphism-invariant right R-module and Y is an automorphism-invariant right S-module.