共查询到20条相似文献,搜索用时 15 毫秒
1.
Li-Xin Mao 《Proceedings Mathematical Sciences》2008,118(4):557-567
A ring is called right P-coherent if every principal right ideal is finitely presented. Let M
R
be a right R-module. We study the P-coherence of the endomorphism ring S of M
R
. It is shown that S is a right P-coherent ring if and only if every endomorphism of M
R
has a pseudokernel in add M
R
; S is a left P-coherent ring if and only if every endomorphism of M
R
has a pseudocokernel in add M
R
. Some applications are given. 相似文献
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3.
A module M is called strongly FP-injective if Exti(P,M) = 0 for any finitely presented module P and all i≥1. (Pre)envelopes and (pre)covers by strongly FP-injective modules are studied. We also use these modules to characterize coherent rings. An example is given to show that (strongly) FP-injective (pre)covers may fail to be exist in general. We also give an example of a module that is FP-injective but not strongly FP-injective. 相似文献
4.
K. Khashyarmanesh Sh. Salarian 《Proceedings of the American Mathematical Society》2003,131(8):2329-2335
Let be a commutative Noetherian ring with nonzero identity and let the injective envelope of be flat. We characterize these kinds of rings and obtain some results about modules with nonzero injective cover over these rings.
5.
A ring R is called left P-coherent in case each principal left ideal of R is finitely presented. A left R-module M (resp. right R-module N) is called D-injective (resp. D-flat) if Ext1(G, M) = 0 (resp. Tor1(N, G) = 0) for every divisible left R-module G. It is shown that every left R-module over a left P-coherent ring R has a divisible cover; a left R-module M is D-injective if and only if M is the kernel of a divisible precover A → B with A injective; a finitely presented right R-module L over a left P-coherent ring R is D-flat if and only if L is the cokernel of a torsionfree preenvelope K → F with F flat. We also study the divisible and torsionfree dimensions of modules and rings. As applications, some new characterizations of von Neumann regular rings and PP rings are given. 相似文献
6.
Let R be a commutative ring. We investigate the relationship between (pre)covers ((pre)envelopes) of an R-module and the counterparts of the corresponding homomorphism module or tensor product module. Some applications are also given. 相似文献
7.
通过引用P-平坦模的定义,引入了右IPF环的概念,推广了右IF环的概念,这对研究IF环及QF环具有重要的作用,同时对右IPF环的性质作了一些刻画,得到了右IPF环的若干个等价命题;最后,用P-平坦模及右IPF环推出了正则环的一些等价条件. 相似文献
8.
Let R be a ring and S a class of R-modules. S-superfluous epimorphisms and S-essential monomorphisms are introduced and studied in this article. As appli-cations, some new characterizations of yon Neumann regular rings and perfect rings are given. Finally, these notions are also used to study minimal homomorphisms. 相似文献
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10.
A. A. Tuganbaev 《Mathematical Notes》1999,65(6):739-748
This paper continues the study of Noetherian serial rings. General theorems describing the structure of such rings are proved.
In particular, some results concerning π-projective and π-injective modules over serial rings are obtained.
Translated fromMatematicheskie Zametki, Vol. 65, No. 6, pp. 880–892 June, 1999. 相似文献
11.
耿玉仙 《数学物理学报(B辑英文版)》2010,30(4):1029-1043
Let R be a ring. We define a dimension, called P-cotorsion dimension, for modules and rings. The aim of this article is to investigate P-cotorsion dimensions of modules and rings and the relations between P-cotorsion dimension and other homological dimensions. This dimension has nice properties when the ring in consideration is generalized morphic. 相似文献
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13.
In this paper we prove that any sheaf of modules over any topological space (in fact, any -module where is a sheaf of rings on the topological space) has a flat cover and a cotorsion envelope. This result is very useful, as we shall explain later in the introduction, in order to compute cohomology, due to the fact that the category of sheaves ( -modules) does not have in general enough projectives.
14.
Guocheng Dai 《代数通讯》2018,46(3):1267-1271
In this paper, we prove that a ring R is left coherent if and only if the class 𝒜bs of absolutely pure left R-modules is a covering class. 相似文献
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16.
Xiaoyan Yang 《代数通讯》2013,41(1):131-142
In this article, FP-injective complexes are introduced and studied. We prove that (⊥??, ??) is a hereditary cotorsion theory if and only if R is a left coherent ring, where ?? denotes the class of all FP-injective complexes of left R-modules. Simultaneously, we study the existence of FP-injective preenvelopes and FP-injective covers. 相似文献
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18.
Alina Iacob 《代数通讯》2017,45(5):2238-2244
We prove that the class of Gorenstein injective modules is both enveloping and covering over a two sided noetherian ring such that the character modules of Gorenstein injective modules are Gorenstein flat. In the second part of the paper we consider the connection between the Gorenstein injective modules and the strongly cotorsion modules. We prove that when the ring R is commutative noetherian of finite Krull dimension, the class of Gorenstein injective modules coincides with that of strongly cotorsion modules if and only if the ring R is in fact Gorenstein. 相似文献
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A principal right ideal of a ring is called uniquely generated if any two elements of the ring that generate the same principal right ideal must be right associated (i.e., if for all a,b in a ring R, aR = bR implies a = bu for some unit u of R). In the present paper, we study “uniquely generated modules” as a module theoretic version of “uniquely generated ideals,” and we obtain a characterization of a unit-regular endomorphism ring of a module in terms of certain uniquely generated submodules of the module among some other results: End(M) is unit-regular if and only if End(M) is regular and all M-cyclic submodules of a right R-module M are uniquely generated. We also consider the questions of when an arbitrary element of a ring is associated to an element with a certain property. For example, we consider this question for the ring R[x;σ]∕(xn+1), where R is a strongly regular ring with an endomorphism σ be an endomorphism of R. 相似文献