arXiv subjects

F. C. Leary

Publications and source records attributed to F. C. Leary.

2 recordsLinked to original sources

arXiv2022

Hopfian and co-Hopfian modules over Artinian rings

An $R$-module $M$ is Hopfian (co-Hopfian) if any epic (monic) endomorphism of $M$ is an automorphism. If $R$ is commutative Noetherian, we characterize the co-Hopfian injective $R$-modules, and the Hopfian injectives in the case that $R$ is also reduced. For a commutative Artinian principal ideal ring, we show that $M$ is Hopfian (co-Hopfian) if and only if $M$ is finitely generated if and only if its injective envelope $E(M)$ is Hopfian (co-Hopfian) if and only if $E(M)$ is finitely generated. We identify the obstacle to generalizing this result to arbitrary Artinian principal ideal rings.

math.AC↗

arXiv2022

co-Hopfian Modules

If $R$ is a ring with 1, we call a unital left $R$-module $M$ co-Hopfian (Hopfian) in the category of left $R$-modules if any monic (epic) endomorphism of $M$ is an automorphism. For commutative Noetherian $R$ we use results of Matlis to show that in a certain context every submodule of a co-Hopfian injective module is co-Hopfian. For these same $R,$ we characterize when a finitely generated co-Hopfian module has finite length. We describe the structure of Hopfian and co-Hopfian abelian groups whose torsion subgroup is cotorsion.

math.AC↗