内射模的t－平坦性

设Ｒ为环，ｔ是左Ｒ－模范畴的一个遗传挠理论．文中证明了下述各点等价：（１）每个内射左Ｒ－模是ｔ－平坦的；（２）每个ｔ－有限表现左Ｒ－模的内射包络是ｔ－平坦的；（３）每个ｔ－有限表现左Ｒ－模是自由Ｒ－模的子模；（４）每个ｔ－有限表现左Ｒ－模是自反的且其对偶模是Ｈ－有限生成的．     

The connes spectrums of certain finite non-abelian groups

In this article, we investigate when every simple module has a projective (pre)envelope. It is proven that (1) every simple right R-module has a projective preenvelope if and only if the left annihilator of every maximal right ideal of R is finitely generated; (2) every simple right R-module has an epic projective envelope if and only if R is a right PS ring; (3) Every simple right R-module has a monic projective preenvelope if and only if R is a right Kasch ring and the left annihilator of every maximal right ideal of R is finitely generated.     

Characterizations of F-V-rings by Quasi-continuous Modules

ＣｈａｒａｃｔｅｒｉｚａｔｉｏｎｓｏｆＦ－Ｖ－ｒｉｎｇｓｂｙＱｕａｓｉ－ｃｏｎｔｉｎｕｏｕｓＭｏｄｕｌｅｓＬｉｕＺｈｏｎｇｋｕｉ（刘仲奎）（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，ＮｏｒｔｈｕｅｓｔＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ，Ｌａｎｃｈ...     

相对n-FP-内射模

给出了n-FP-内射模的定义,M为左R-模,如果对任意的左R-模N有Ext1(N,M)=0,则称M为n-FP-内射模,作为应用,给出了n-FP-内射模的一些等价条件.     

关于所有子模是纯子模的平坦模

引进了一新模类-完全平坦模(每一个商模平坦).并得到了:令M是平坦左R-模,RM是完全平坦模当且仅当RM的所有子模是纯的当且仅当每一个右R-模A是M-平坦的.同时本文用完全平坦模刻画了V.N.正则环.     

广义逆多项式模的co-Hopf性质

设R是结合环(可以没有单位元),(S,≤)是严格全序幺半群,序≤是Artin的且对任意s∈S,有0≤s,则对任意具有性质(F)的左R-模M,[MS,≤]是co-Hopf左[[RS,≤]]一模当且仅当M是co-Hopf左R-模.     

On the existence of covers by injective modules relative to a torsion theory

Let R be a ring with identity. In this note we study covers of left R-modules by r-injectives left R-modules, where r is a hereditary torsion theory defined in the category of all left R-modules and all R-morphisms. When R is an artinian commutative ring, a complete answer about the existence of such covers for every R-module is given. In case that T is a centrally splitting torsion theory, we can characterize those T for which every left R-module has a T-injective cover. Also we analyze R-modules such that the injective and the T-injective cover are the same. At the end of this note we relate the concepts of colocalization and cover     

同调方程

设Ｒ是左、右凝聚环,Ｒ~ωＲ是一个忠实平衡自正交双模．对有限表现左Ｒ－模Ａ和正整数ｎ,本文研究了形如,　的同调方程．给出了模范畴为有限表现右Ｒ-模｝是子模闭的充要条件,并举例说明了该模范畴并非总是子模闭的,     

左连续环中若干链条件的等价性

(1)设R是左连续环,则R是左Artin环当且仅当R满足左限制有限条件当且仅当R关于本质左理想满足极小条件当且仅当R关于本质左理想满足极大条件.同时给出一个左自内射环是QF环的充要条件;(2)证明了左Z₁-环上的有限生成模都有Artin-Rees性质.     

Gorenstein dimensions of unbounded complexes and change of base (with an appendix by Driss Bennis)

For a commutative ring R and a faithfully flat R-algebra S we prove,under mild extra assumptions,that an R-module M is Gorenstein flat if and only if the left S-module S?_R M is Gorenstein flat,and that an R-module N is Gorenstein injective if and only if it is cotorsion and the left S-module Hom R(S,N)is Gorenstein injective.We apply these results to the study of Gorenstein homological dimensions of unbounded complexes.In particular,we prove two theorems on stability of these dimensions under faithfully flat (co-)base change.     

FP-内射环的一个特征

本文首次利用投射模给出了右ＦＰ-内射环的一个外部特征，即Ｒ为右ＦＰ-内射环当且仅当投射左Ｒ-模的有限生成子模为闭子模。     

关于基本可数生成子模的扩张性

称左R-模M是ecg-扩张模,如果M的任意基本可数生成子模是M的直和因子的基本子模.在研究了ecg-扩张模的基本性质的基础上,本文证明了对于非奇异环R,所有左R-模是ecg-扩张模当且仅当所有左R-模是扩张模.同时我们还用ecg-拟连续模刻画了Noether环和Artin半单环.     

2型X—extending模与Osofsky—smith定理

设R是有单位元的环，X是所有半单左R一模及Singular左R－模构成的模类，M是循环的extending左R一模，本文证明了若M的所有循环子商都是2型X－extending模，则M具有有限一致维数，该结果推广了著名的Osofsky-Smith定理。     

投射可迁环上矩阵环的若当同态

设R′是一个环,Mn′（R′）是R′上的n′×n′矩阵环.如果环R有不变基数性质并且每个有限生成的投射左R-模是自由模,则R是一个投射自由环.如果环R≌Mr（S）,其中S是一个投射自由环,则R是一个投射可迁环.当R是一个投射可迁环时,给出了从Mn′（R′）到Mn（R）（n′≥n≥2）的若当同态的代数公式.     

关于E_ω-投射模和E_ω-内射模(英文)

左R-模M称为Eω-内射模,如果对环R中任意的ω阶Euclid理想I来说,任何R-模同态能够拓展为R-模同态。左R-模M称为Eω-投射模,若对环R中任意的ω阶Euclid理想I和任何R-模同态f∈HomR(M,R/I),存在R-模同态g∈HomR(M,R)使得f=πg,其中π是自然同态。本文证明P和Q均是Eω-投射模当且仅当PQ是Eω-投射模。进而,又证明了每一个左R-模是Eω-投射的当且仅当每一个左R-模是Eω-内射。     

MORPHIC MODULES

A module M is called morphic if M/M α ? ker(α) for all endomorphisms α in end(M), and a ring R is called a left morphic ring if _RR is a morphic module. We consider the open question when the matrix ring M_n(R) is left morphic by relating it to when Rⁿ is morphic as a left R-module. More generally, we investigate when M being morphic implies that end(M) is left morphic, and conversely. Finally, we relate the morphic condition to internal cancellation in the module.     

PI-rings and semiprime rings having faithful modules with krull dimension

It is proved that if a PI-ring R has a faithful left R-module M with Krull dimension, then its prime radical rad(R) is nilpotent. If, moreover, the R-module M and the left ideal_R(rad(R)) are finitely generated, then R has a left Krull dimension equal to the Krull dimension of M. It turns out that a semiprime ring, which has a faithful (left or right) module with Krull dimension, is a finite subdirect product of prime rings. Moreover, first, a right Artinian ring R such that rad(R)²=0 has a faithful Artinian cyclic left module, and second, a finitely generated semiprime PI-algebra over a field has a faithful Artinian module. We give examples showing that the restrictions imposed are essential, as well as an example of a finitely generated prime PI-algebra over a field, which is not Noetherian and has a Krull dimension. Supported by RFFR grant No. 26-93-011-1544. Translated fromAlgebra i Logika, Vol. 36, No. 5, pp. 562–572, September–October, 1997.     

广义拟内射模的自同态环

本文的目的,是推广[1]中定理1.22和[2]中命题1(1).我们得到:设R是环,且Q=End_R(M),其中M是广义拟内射模.那么有(1)J(Q)=Z(Q);(2)Q/J(Q)是Von Neumann正则环.     

Free modules over hjelmslev rings in which not every maximal linearly independent subset is a basis

First it will be shown that every left-noetherian AH-ring is left-artinian. For an AH-ring R every finite linearly independent subset of a free left R-module V can be completed to a basis of V. But a maximal linearly independent subset of a free left R-module V need not be a basis of V. For an H-ring R, every maximal linearly independent subset of a free left R-module V is a basis of V if and only if the H-ring R is left-noetherian or V is finitely generated.