Two characterizations of pure injective modules

Abstract

Let $R$ be a commutative ring with identity and $D$ an $R$-module. It is shown that if $D$ is pure injective, then $D$ is isomorphic to a direct summand of the direct product of a family of finitely embedded modules. As a result, it follows that if $R$ is Noetherian, then $D$ is pure injective if and only if $D$ is isomorphic to a direct summand of the direct product of a family of Artinian modules. Moreover, it is proved that $D$ is pure injective if and only if there is a family $\{T_{\lambda }{\}}_{\lambda \in \Lambda }$ of $R$-algebras which are finitely presented as $R$-modules, such that $D$ is isomorphic to a direct summand of a module of the form ${\Pi }_{\lambda \in \Lambda }{E}_{\lambda }$ where for each $\lambda \in \Lambda$, $E_{\lambda }$ is an injective $T_{\lambda }$-module.

8 pages, to appear in Proc. Amer. Math. Soc