A generalization of purely extending modules relative to a torsion theory

TL;DR

This paper introduces $ au_{s}$-extending modules, a torsion-theoretic generalization of extending modules, and explores their properties, including flatness of certain modules and classification of rings with this property.

Contribution

It defines $ au_{s}$-extending modules and extends many classical results to this new concept, including conditions for flatness and ring classifications.

Findings

Purely $ au_{s}$-extending rings imply flatness of cyclic $ au$-nonsingular modules.

The property holds over principal ideal domains.

Classification of rings based on direct sums being purely $ au_{s}$-extending.

Abstract

In this work we introduce a new concept, namely, $\tau_{s}$-extending modules (rings) which is torsion-theoretic analogues of extending modules and then we extend many results from extending modules to this new concept. For instance we show that for any ring $R$ with unit, if $R$ is purely $\tau_{s}$-extending then every cyclic $\tau$-nonsingular $R$-module is flat and we show that this fact is true over a principal ideal domain as well. Also, we make a classification for the direct sums of the rings to be purely $\tau_{s}$-extending.