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On the existence of nonzero injective covers and projective envelopes of modules
Author(s) -
Xiaoxiang Zhang,
Song Xian-mei
Publication year - 2013
Publication title -
turkish journal of mathematics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.454
H-Index - 27
eISSN - 1303-6149
pISSN - 1300-0098
DOI - 10.3906/mat-1203-24
Subject(s) - mathematics , injective function , cover (algebra) , projective cover , envelope (radar) , ring (chemistry) , injective module , simple module , primitive ring , simple (philosophy) , pure mathematics , zero (linguistics) , projective test , combinatorics , principal ideal ring , projective space , collineation , commutative ring , computer science , philosophy , chemistry , engineering , telecommunications , epistemology , commutative property , mechanical engineering , radar , organic chemistry , linguistics
In general, the injective cover (projective envelope) of a simple module can be zero. A ring R is called a weakly left V-ring (strongly left Kasch ring) if every simple left R-module has a nonzero injective cover (projective envelope). It is proven that every nonzero left R-module has a nonzero injective cover if and only if R is a left Artinian weakly left V-ring. Dually, every nonzero left R-module has a nonzero projective envelope if and only if R is a left perfect right coherent strongly left Kasch ring. Some related rings and examples are considered. © Tübi̇tak.

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