On  Lifting LE- Modules

Derya Keskin and Christian Lomp


Abstract

     Let $R$ be an associative ring with identity and $M$ a right $R$-module. $M$ is called a {\em lifting LE-module} if $M$ is lifting and $M= \oplus_{i \in I} M_i$, where $M_i$ is a module with local endomorphism ring, for all $i \in I$. The purpose of this paper is to investigate some properties of these modules. Semiperfect rings such  that any direct sum of a simple and a projective local mudule is lifting are characterized as semiprimary rings with Jacobson radical square-zero. Moreover we characterize the class of lifting LE-modules $M$ such that $M\oplusS$ is lifting for all semisimple modules $S$ as those modules that are direct sums of hollow LE-modules which are extensions of a semisimple by a simple module. Finally we show that this class coincides with the class of semisimple modules if and only if every extension of two simple modules splits.