MPI-环和半局部环的等价条件

§1.MPI-环的结构和性质本文中的环均指有单位元的交换环。设R是环,SpecR是R的所有素理想的集合按照Zariski拓扑作成的拓扑空间,称之为R的素谱空间,其闭集和开集分别为     

Г-环的单位元

Γ-环的乘法单位元比结合环的乘法单位元更复杂,更富有变化.首先它有单位元,α-单位元(强单位元)之分,其次它具有与结合环单位元相异的性质,对此本文逐一阐述.此外还探讨了Γ-环M与其矩阵环M_m,n单位元间的关系.在导入Γ-环的特征这一概念后,证明了具有单位元Γ-环的特征的一些性质.     

环上矩阵环的导子

文[1]讨论了除环上2阶全矩阵环的导子的一些性质,本文继此讨论一般结合环R上的R阶全矩阵环R_n的导子的性质.环R的加群自同态(?)称为R的导子,若对x、y∈R,有d(xy)=xd(y) d(x)y.如下总假定R有单位元,且用R_n表示R上的n阶全矩阵环,E_ij表示(i,j)位置元素为R的单位元1其余元素为零的R_n的矩阵单位,xE饰表示对角线上元素为x的数量阵.     

H0R结构刻画环R

对于可换环R,通过考察H0R的结构和性质给出了环R的有关刻画.以H0结构为工具,利用相关环还得到了K0R的CPF性、连通性等的重要特征.     

稳定环与其上的二维线性群

本文首先引入非交换的单位稳定环的概念,即令R是有1的结合环,若r、s、a、b∈R,满足关系式ar bs=1,有c∈R使得r cs=unit,则称R是左1-稳定的;若c可取到单位u使r us=unit,称R为左单位稳定的。类似地可得R为右单位稳定及单位稳定的概念。然后,证明了强正则环、Artin环是单位稳定环,同时得出了单位稳定环的一些性质。其次,引入了双1-单位稳定环的概念,即对任意a_1,a_2∈R,存在λ∈U,使得1十λa_2=unit,1 a_2λ~(-1)=unit。然后给出了双1-单位稳定环上的二维线性群的定义关系。     

稳定环与其上的二维线性群

本文首先引入非交换的单位稳定环的概念,即令R是有1的结合环,若r、s、a、b∈R,满足关系式ar bs=1,有c∈R使得r cs=unit,则称R是左1-稳定的;若c可取到单位u使r us=unit,称R为左单位稳定的。类似地可得R为右单位稳定及单位稳定的概念。然后,证明了强正则环、Artin环是单位稳定环,同时得出了单位稳定环的一些性质。其次,引入了双1-单位稳定环的概念,即对任意a_1,a_2∈R,存在λ∈U,使得1 λa_1=unit,1 a_2~(λ-1)=unit。然后给出了双1-单位稳定环上的二维线性群的定义关系。     

一般环的广义弱clean指数（英文）

一般环(未必有单位)中的元素a称为clean,若其可表为一个幂等元和一个Q(R)中元素之和;一般环I称为clean general环,若环I中元素都是clean的.受clean和弱clean指数概念的启发,我们给出对于一般环的一类新的指数——广义弱clean指数,给出该指数的一些性质,并且证明了一般环的广义弱clean指数为1时,该环为abelian环.进一步地,我们给出一般环的广义弱clean指数为2或3时环的性质刻画,得到了一些有关矩阵环的广义弱clean指数的性质.而对于一些在文献中已有的结论,我们给出其推广形式.     

环上可加左导子的刻画

令A与B是含单位元的环,M是(A,B)-双模,U=Tri(A,M,B)是三角环.在一些附加假设条件下,本文从几个不同的角度给出了U上可加左导子的结构性质.此外,也得到了满足一定条件的环上可加左导子的两个不同刻画.     

单因环的性质、等价条件和结构

一个有单位元的结合环，如果其元素不是单位就是零因子，则称其为单因环。它是很广泛的一个环类．本文讨论了单因环的住质、等价条件和结构；还讨论了它同其它环诸如正则环、局部环和循环环的关系，从而较深刻地刻划了这种环。     

Z／（p^e）上分裂环的结构

本文研究了环ｚ／（ｐｅ）上多项式的性质和分裂环的结构．主要分析了分裂环中元素的极小多项式，零化理想的结构，和分裂环子环性质．     

On the Structure of the Units of Group Algebra of Dihedral Group

In this paper, we completely determine the structure of the unit group of the group algebra of some dihedral groups D2 n over the finite field Fpk, where p is a prime.     

The Engel Length of the Product of Engel Elements

Considering the relation between the Engel lengths of elements and their product, we give a counterexample to Question 11.88 in the “Kourovka Notebook” [1].     

Spectra of finite linear and unitary groups

The spectrum of a finite group is the set of its element orders. An arithmetic criterion determining whether a given natural number belongs to a spectrum of a given group is furnished for all finite special, projective general, and projective special linear and unitary groups. Supported by RFBR (grant Nos. 08-01-00322 and 06-01-39001) and by the Council for Grants (under RF President) and State Aid of Leading Scientific Schools (project NSh-344.2008.1). __________ Translated from Algebra i Logika, Vol. 47, No. 2, pp. 157–173, March–April, 2008.     

On Complemented Subgroups of Finite Groups

51. IntroductionIt is quite clear that the ekistence of complements for some families of subgroups of agroup gives a lot ofinfor~ion about its structure. FOr instance, Hall[6] proved that a groupG is supersoluble with elementary abelian Sylow subgroups if and only if G is complemellted,that is, every subgroup of G is comPlemeded in G. The same anchor also proved that agroup is soluble if and only if every Sylow subgroup is complemellted (see [3;I,3.5]). Morerecelltly, Arad and Wardll] pro…     

Classes of abelian groups related to sequential convergence

We study classes of abelian groups related to sequential com¬pactness and its generalizations (completeness, coarseness and sequential pre-compactness) in convergence groups. In particular, we describe the algebraic structure of the abelian groups on which every coarse convergence is complete and we prove that: i) every abelian group admits a sequentially precompact convergence; ii) every algebraically compact abelian group admits a sequen¬tially compact convergence.     

Notions of Discrimination

As an outgrowth of the study of algebraic geometry over groups, discriminating groups were introduced. Many important universal type groups such as Higman's universal group and Thompson's group F were shown to be discriminating. Squarelike groups were then introduced to better capture axiomatic properties of discrimination. In the present article squarelike groups are reinterpreted in terms of discrimination of quasi varieties, and the relationship with an older version of discrimination, termed varietal discrimination here, is studied.     

双曲群,自动机群与群的Dehn函数

本文第一部分对组台群论的发展史作了一个简要的回顾．然后重点介绍近20年来组合群论领域中的三个热点课题：即双曲群，自动机群和群的Dehn函数的有关概念，并对相关的重要研究成果给予概述，其中包括作者本人在群的二阶Dehn函数的研究工作中的若干成果．最后提出9个公开问题。     

几类非Abel群之增广商群的结构

记ZG为有限群G的整群环,△n(G)为增广理想△(G)的n次幂,Qn(G)=△"(G)/△n 1(G)为G的增广商群.本文考虑了二面体群D2tk(k 奇)和m次对称群Sm,证明了Qn(D2tk)为秩不超过2t 1的基本2-群以及Qn(Sm)≌Z2.     

Quasi-isometrically embedded subgroups of braid and diffeomorphism groups

We show that a large class of right-angled Artin groups (in particular, those with planar complementary defining graph) can be embedded quasi-isometrically in pure braid groups and in the group of area preserving diffeomorphisms of the disk fixing the boundary (with respect to the -norm metric); this extends results of Benaim and Gambaudo who gave quasi-isometric embeddings of and for all . As a consequence we are also able to embed a variety of Gromov hyperbolic groups quasi-isometrically in pure braid groups and in the group . Examples include hyperbolic surface groups, some HNN-extensions of these along cyclic subgroups and the fundamental group of a certain closed hyperbolic 3-manifold.