An Approach to Injective Acts over Monoids Based on Indecomposability

The main purpose of this paper is investigating classes of acts that are injective relative to all embeddings with indecomposable domains or codomains. We give some homological classifications of monoids in light of such kinds of injectivity. Our approach to indecomposable property provides a new characterization of right absolutely injective monoids as ones that all indecomposable acts are injective.