关于两类有限单群中的换位元

群G中一个元素x称作是G中的一个换位元,如果x=aba~(-1)b~(-1),这里由G中一切换位元所生成的子群称为G的换位子群,通常记作G＇。如果G为非交换单群,则G=G＇。因而G中每个元素均可表为有限个换位元的乘积。在[1]中O.Ore提出了如下的猜想:在一个有限非交换单群中,每一个元素都可以表成换位元的形式。在同一文     

一个新十二参矩形元

本文用“双参数法”提出了一个新的十二参矩形元，并证明了其收敛性，同时分析了该元与著名的ＡＣＭ元及十二参广义协调元之间的关系。     

小 Janko群 J_1的换位元

设群 G 是有限群,a,b∈G,称 a~(-1)b~(-1)ab 为 G 的一个换位元.由 G 的全部换位元生成的子群 G′称为 G 的换位子群.很明显,G′是 G 的正规子群.当 G 是非交换单群时,G′=G,这说明,任何一个非交换单群 G 的每个元素都是 G 的换位元的乘积.但是否就     

四节点元和八节点h－收敛的比较

本文从理论上比较了四边形四节点元和四边形八节点元的ｈ－收敛性，得出八节点元较四节点元有较快收敛率的结论．并通过算例进行了验证．     

分子格半群

在本文中，作者在格半群上引入了半群元和理想元的概念，使得半群（理想）和ＴＬ－Ｆｕｚｚｙ半群（理想）是其特例。在分子格半群上引入了群元和正规群元等概念，在更高的层次上统一了群和Ｌ－Ｆｕｚｚｙ群。     

半群环的幂等元

讨论了半群环R[S]的幂等元问题．对[1]提出的公开问题9作了一个肯定回答，同时就一般半群环的幂等元的具体形式作了深入的研究，给出了若干情形下的幂等元刻划．     

12参双参数矩形板元的误差估计

双参数方法是构造高阶问题有限元的有效方法．以此方法构造的双参数元是一种非标准元，以往文献中只证明了它的收敛性．此文针对具体12参双参数矩形板元给出它的误差估计式，并分析了节点参数的扰动量．文中的分析方法也适合于其它双参数矩形板元的误差估计．     

四节点元和八节点元h—收敛的比较

本文从理论上比较了四边形四节点元和四边形八节点元的ｈ－收敛性，得出八节点元较四节点元有较快收敛率的结论，并通过算例进行了验证。     

关于RC-正则环

我们利用ralated单位正则元刻西了正则环的比较结构．进而把文[2]定理中的related单位元推广到了related单位正则元，并给出了RC-正则环的—个局部特征．     

正规软代数的性质与等价刻划

本文利用软代数的奇元、偶元、中性元及中理想等概念对正规软代数的性质进行了讨论，并给出了正规软代数的几种等价刻划。     

Quasirecognizability by the Set of Element Orders for Groups 3 D 4(q), for q Even

It is proved that if G is a finite group with an element order set as in the simple group ³D₄(q), where q is even, then the commutant of G/F(G) is isomorphic to ³D₄(q) and the factor group G/G′ is a cyclic {2, 3}-group. __________ Translated from Algebra i Logika, Vol. 45, No. 1, pp. 3–19, January–February, 2006.     

The commutator width of elements in a wreath product of free abelian groups

We set forth an algorithm for computing the commutator width of an arbitrary element in the commutant of a discrete wreath product of free abelian groups.     

Relaxation of metric constrained interpolation and a new lifting theorem

In this paper a new lifting interpolation problem is introduced and an explicit solution is given. The result includes the commutant lifting theorem as well as its generalizations in [27] and [2]. The main theorem yields explicit solutions to new natural variants of most of the metric constrained interpolation problems treated in [9]. It is also shown that via an infinite dimensional enlargement of the underlying geometric structure a solution of the new lifting problem can be obtained from the commutant lifting theorem. However, the new setup presented obtained from the commutant lifting theorem. However, the new setup presented in this paper appears to be better suited to deal with interpolations problems from systems and control theory than the commutant lifting theorem.Dedicated to Israel Gohberg, as a token of admiration for his inspiring work in analysis and operator theory, with its far reaching applications, in friendship and with great affection.     

Commutants modulo the compact operators of certain CSL algebras II

The commutant modulo compacts, or essential commutant, of a reflexive algebra with commutative subspace lattice is a C^* algebra which is the sum of the compact operators in L(H) and a C^* subalgebra of the core. We give a characterization of the essential commutant of a separably acting CSL algebra in terms of properties of the spectral measure of an operator in the intersection of the essential commutant and the core. This is used to determine some sufficient conditions on the lattice for when the essential commutant is norm generated by the projections it contains.     

Semiautomorphic inverse property loops

We define a variety of loops called semiautomorphic, inverse property loops that generalize Moufang and Steiner loops. We first show an equivalence between a previously studied variety of loops. Next we extend several known results for Moufang and Steiner loops. That is, the commutant is a subloop and if a is in the commutant, then a² is a Moufang element, a³ is a c-element and a⁶ is in the center. Finally, we give two constructions for semiautomorphic inverse property loops based on Chein’s and de Barros and Juriaans’ doubling constructions.     

The commutant of the Volterra operator

It is proved by elementary methods that the strongly closed algebra generated by the Volterra operator V is the commutant of V.     

Unbounded commutants and intertwining spaces of unbounded symmetric operators and 1-representations

This paper investigates the strong commutant, the weak commutant and the form commutant of an unbounded symmetric (nonself-adjoint) operator and of an unbounded 1-representation on a Hilbert space. For two examples of unbounded symmetric operators these commutants are described in terms of singular integral operators and of Toeplitz operators, respectively.     

On reachable elements and the boundary of nilpotent orbits in simple Lie algebras

Let g be a simple Lie algebra. An element x∈g is said to be reachable, if it is contained in the commutant of its centraliser. Any reachable element is necessarily nilpotent. We study various properties of reachable elements, and a relationship between the property of being reachable and the codimension of the boundary of the corresponding orbit. Some general estimates for the boundary of an arbitrary nilpotent orbit is given.     

Certain Jordan operator algebras and double commutant theorems

Two operations on sets of bounded operators on Hilbert space are studied: One produces Jordan algebras and the other, its inverse in a certain sense, produces self-adjoint linear spaces. The question of which Jordan algebras arise from the first of these operations is investigated. It is shown that, in many cases, R has this property if and only if the complex associative algebra R + iR is equal to its double commutant. Thus, a by-product of the study is another approach to double commutant theorems.