Abel群的一些分解定理的推广(Ⅲ)

从主理想整环上有界模分解的Prüfer-Baer定理出发,研究(无限维)向量空间的代数的线性变换的几个基本问题,得到了如下结果:设V是域F上的(无限维)向量空间,A是V上的一个代数的线性变换,则有(1)若任何与A可交换的线性变换均与线性变换B可交换,则B=f(A),其中f是F上的多项式.进而线性变换B也是代数的.(2) V中存在一组基,使A在这组基下的矩阵是有理标准型(经典标准型)矩阵.当F是代数闭域时,经典标准型矩阵即为若当标准型矩阵.(3)当F是代数闭域时,A存在相应的Jordan-Chevalley分解.进一步,该结论在完全域上仍成立.这些研究推广了有限维向量空间上线性变换的相关结果.     

关于线性变换的像空间与核空间的直和

讨论数域P上有限维线性空间V上线性变换A的方幂A~k的像空间ImA~k与核空间KerA~k的直和,并将结论推广到无限维线性空间.证明了:V=ImA~k+KerA~k当且仅当ImA~k=ImA~(k+1),以及ImA~k∩KerA~k=0当且仅当KerA~k=KerA~(k+1).     

广义扩张的Schr?dinger-Virasoro代数的二上同调群

假设F是特征为0的域,Γ是F上的一个加法子群,域F上的元s满足s?Γ但2s∈Γ.我们定义了一类无限维李代数W[Γ,s],称之为广义扩张的Schr?dinger-Virasoro代数.本文确定了W[Γ,s]上的所有二上同调群.     

一类无限维完备李代数的2-局部齐次导子北大核心CSCD

通过对复数域上单李代数的Loop代数进行一维导子扩张,得到一类无限维完备李代数;利用其根空间分解及无外导子的性质,证明了这类无限维完备李代数的2-局部齐次导子都是导子.     

矩阵代数上的几种线性变换及其相互关系

本文给出了数域F上n阶矩阵空间上的几种特殊线性变换的定义,研究了这几种线性变换的关系,从而使得文献[2],[3]的结果成为本文的推论,进一步得到这些线性变换的不动点子空间基与维数.     

广义扩张的Schr?dinger-Virasoro代数的导子

假设F是特征为0的域,Γ是F上的加法子群,域F上的某个元s满足s■Γ但2s∈Γ,本文定义了一类无限维李代数,称之为广义扩张的Schrodinger-Virasoro代数W,[Γ,s].本文确定了     

与线性变换的完全环同构的环理论(Ⅲ)

<正> 本文继上文[1,2]的理论,对线性变换完全环的结构作进一步研究.在§1中我们讨论一般无限矩阵的几何意义.在§2中我们用有限维向量空间的线性变换完全环来构作无限维向量空间的线性变换完全环.我们的思想方法是:设是向量空间,     

线性变换的值域与核的维数关系定理的证法探析

本文首先证明了有限维线性空间上的线性变换是单射当且仅当它是满射这一结论,其次分析了通常高等代数教材中关于线性变换的值域与核的维数关系定理的两种证明方法,并给出了该定理的一种新的证明方法.     

具有非退化Killing型的广义李超代数

设F是特征数为零的域.本文证明了F上的有限维广义李超代数的Killing型是相容的、不变的与上对称的.进而证明了具有非退化Killing型的有限维广义李超代数的 若干性质，最后得出这种广义李超代数必为有限个典型的广义李超代数的直积.     

域扩张时的李代数扩张

设E是特征零的代数封闭域,LE是E上L型有限维单李代效,F是E的包含素子域Q的子域,且|E:F]<∞.本文引入李代数的准子代数的概念,且F上同类型李代数LF就是LE的准子代数.本文定出了LE的包含LF的所有准子代数.     

广义Weyl型李代数Wgl_n(F)上的2-上同调群

设F是一特征为零的域,W是F上的广义Weyl代数,gl_n(F)为F上的一般线性李代教,则结合代数Wgl_n(F)上具有一个诱导的李代数结构,本文讨论了李代数Wgl_n(F)的2-上同调群的结构.     

On Semitransitive Collections of Operators

A collection F of operators on a vector space V is said to be semitransitive if for every pair of nonzero vectors x and y in V there exists a member T of F such that either Tx = y or Ty = x (or both). We study semitransitive algebras and semigroups of operators. One of the main results is that if the underlying field is algebraically closed, then every semitransitive algebra of operators on a space of dimension n contains a nilpotent element of index n. Among other results on semitransitive semigroups, we show that if the rank of nonzero members of such a semigroup acting on an n-dimensional space is a constant k, then k divides n.     

The mod 2 Homology of the General Linear Group of a 2-adic Local Field

Let F be a finite extension of the 2-adic rational numbers. We compute the mod 2 homology of the general linear group GL(F) as a Hopf algebra over the Steenrod algebra. The answer is formulated in terms of the well-known homology algebras of the infinite unitary group U, its classifying space BU, and the classifying space BO of the infinite orthogonal group.     

Infinite dimensional irreducible Lie algebras containing transformations of finite rank

Let be a field of characteristic zero and let V be an infinite dimensional vector space over . A linear transformation x of V is called finitary if . The aim of this paper is to describe irreducible Lie subalgebras of containing nonzero finitary transformations. It turns out that any such algebra is a semidirect product of a finite dimensional Lie algebra and a “dense” Lie subalgebra of for some vector space W. Received January 4, 2000 / Published online March 12, 2001     

Traces on finite \mathcal{W} -algebras

We compute the space of Poisson traces on a classical W \mathcal{W} -algebra, i.e., linear functionals invariant under Hamiltonian derivations. Modulo any central character, this space identifies with the top cohomology of the corresponding Springer fiber. As a consequence, we deduce that the zeroth Hochschild homology of the corresponding quantum W \mathcal{W} -algebra modulo a central character identifies with the top cohomology of the corresponding Springer fiber. This implies that the number of irreducible finite-dimensional representations of this algebra is bounded by the dimension of this top cohomology, which was established earlier by C. Dodd using reduction to positive characteristic. Finally, we prove that the entire cohomology of the Springer fiber identifies with the so-called Poisson-de Rham homology (defined previously by the authors) of the centrally reduced classical W \mathcal{W} -algebra.     

Identities of representations of nilpotent lie algebras

Lret N be a nilpotent of class 2 Lie algebra with one-dimensional centre C = Kc over an infinite field K and let p : N → End_k:(V) be a representation of N in a vector space V such that p(c) is invertible in End_k(V). We find a basis for the identities of the representation p. As consequences we obtain a basis for all the weak polynomial identities of the pair (M₂:(K), s1₂(K)) over an infinite field K of characteristic 2 and describe the identities of the regular representation of Lie algebras related with the Weyl algebra and its tensor powers.     

Study of the cardinalities of linear spaces

The paper discusses the relation between the cardinalities of linear spaces over a number field F and the cardinality of F, and obtains the result that the cardinality of a countable dimensional linear space V(F) equals the cardinality of the number field F. Some examples are given for the cardinality of a general infinite dimensional linear space.     

Finite dimensional semisimple Q-algebras

A Q-algebra can be represented as an operator algebra on an infinite dimensional Hilbert space. However we don’t know whether a finite n-dimensional Q-algebra can be represented on a Hilbert space of dimension n except n = 1, 2. It is known that a two dimensional Q-algebra is just a two dimensional commutative operator algebra on a two dimensional Hilbert space. In this paper we study a finite n-dimensional semisimple Q-algebra on a finite n-dimensional Hilbert space. In particular we describe a three dimensional Q-algebra of the disc algebra on a three dimensional Hilbert space. Our studies are related to the Pick interpolation problem for a uniform algebra.