Generalizations of principally injective rings

SS Page, Y Zhou - Journal of Algebra, 1998 - Elsevier
SS Page, Y Zhou
Journal of Algebra, 1998Elsevier
A ringRis said to be rightP-injective if every homomorphism of a principal right ideal toRis
given by left multiplication by an element ofR. This is equivalent to saying thatlr (a)= Rafor
everya∈ R, wherelandrare the left and right annihilators, respectively. We generalize this to
only requiring that for each 0≠ a∈ R, lr (a) containsRaas a direct summand. Such rings are
called rightAP-injective rings. Even more generally, if for each 0≠ a∈ Rthere exists ann> 0
withan≠ 0 such thatRanis not small inlr (an), Rwill be called a rightQGP-injective ring …
A ringRis said to be rightP-injective if every homomorphism of a principal right ideal toRis given by left multiplication by an element ofR. This is equivalent to saying thatlr(a)=Rafor everya∈R, wherelandrare the left and right annihilators, respectively. We generalize this to only requiring that for each 0≠a∈R,lr(a) containsRaas a direct summand. Such rings are called rightAP-injective rings. Even more generally, if for each 0≠a∈Rthere exists ann>0 withan≠0 such thatRanis not small inlr(an),Rwill be called a rightQGP-injective ring. Among the results for rightQGP-injective rings we are able to show that the radical is contained in the right singular ideal and is the singular ideal with a mild additional assumption. We show that the right socle is contained in the left socle for semiperfect rightQGP-injective rings. We give a decomposition of a rightQGP-injective ring, with one additional assumption, into a semisimple ring and a ring with square zero right socle. In the third section we explore, among other things, matrix rings which areAP-injective, giving necessary and sufficient conditions for a matrix ring to be anAP-injective ring.
Elsevier
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