Modules that are Invariant with Respect to Automorphisms and Idempotent Endomorphisms of Their Hulls and Covers

Abstract

The paper contains both known and new results on automorphism-invariant modules, automorphism-coinvariant modules and modules which are invariant or coinvariant with respect to idempotent endomorphisms of its hull and its cover, respectively. The main results are given with proofs.