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Modules which are invariant under monomorphisms of their injective hulls

Published online by Cambridge University Press:  09 April 2009

A. Alahmadi
Affiliation:
Department of MathematicsOhio UniversityAthens, OH 45701USA e-mail: noyaner@yahoo.com
N. Er
Affiliation:
Department of MathematicsThe Ohio State University-NewarkOH 43055, USA
S. K. Jain
Affiliation:
Department of MathematicsThe Ohio State University-NewarkOH 43055, USA
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Abstract

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In this paper certain injectivity conditions in terms of extensions of monomorphisms are considered. In particular, it is proved that a ring R is a quasi-Frobenius ring if and only if every monomorphism from any essential right ideal of R into R(N)R can be extended to RR. Also, known results on pseudo-injective modules are extended. Dinh raised the question if a pseudo-injective CS module is quasi-injective. The following results are obtained: M is quasi-injective if and only if M is pseudo-injective and M2 is CS. Furthermore, if M is a direct sum of uniform modules, then M is quasi-injective if and only if M is pseudo-injective. As a consequence of this it is shown that over a right Noetherian ring R, quasi-injective modules are precisely pseudo-injective CS modules.

Type
Research Article
Copyright
Copyright © Australian Mathematical Society 2005

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