Matrix Near-rings over Centralizer Near-rings

For a finite group G and a subgroup A of Aut(G), let M_A(G) denote the centralizer near-ring determined by A and G. The group G is an M_A(G)-module. Using the action of M_A(G) on G, one has the n × n generalized matrix near-ring Mat_n(M_A(G);G). The correspondence between the ideals of M_A(G) and those of Mat_n(M_A(G);G) is investigated. It is shown that if every ideal of M_A(G) is an annihilator ideal, then there is a bijection between the ideals of M_A(G) and those of Mat_n(M_A(G);G).1991 Mathematics Subject Classification: 16Y30     

On a Question of J. H. Meyer

Abstract

In this paper, we present a partial solution to the following question of J. H. Meyer (Meyer, J. H. (1986). Matrix Near-Rings. Ph.D. dissertation, University of Stellenbosch, South Africa, Prob. 11): Find a necessary and sufficient condition for a near-ring to be isomorphic to a matrix near-ring. In fact, three characterization results for abstract affine matrix near-rings are given. As a corollary, we get that, for each n ≥ 2, the class of all n × n matrix near-rings over abstract affine near-rings is finitely axiomatizable.     

On Prime and Semiprime Near-Rings with Generalized Derivation

Abstract

Let N be a left near-ring and S be a nonempty subset of N. A mapping F from N to N is called commuting on S if [F(x),x] = 0 for all x € S. The mapping F is called strong commutativity preserving (SCP) on S if [F(x),F(y)] = [x,y] for all x, y € S. In the present paper, firstly we generalize the well known result of Posner which is commuting derivations on prime rings to generalized derivations of semiprime near-rings. Secondly, we investigate SCP-generalized derivations of prime near-rings.     

On an Isomorphism Problem for Endomorphism Near-Rings

Suppose and are endomorphism near-rings generated by
groups of automorphisms containing the inner automorphisms of two respective finite perfect groups and . In this note we show that if and are isomorphic, then and are isomorphic.

     

A note on liftings of modules

Let N be a zero-symmetric right near-ring with identity. In 1993, S. Bagley introduced a construction for N[x], the near-ring of polynomials with coefficients from N. In this paper we study the central elements of N[x], C(N[x]), and we characterize C(N[x]) in terms of C(N) for a class of near-rings. We also introduce a new generalization for the center of a ring to the near-ring case, and we show that this new generalization yields a near-ring which properly contains C(N[x]) for a certain class of near-rings N.     

Centers and Generalized Centers of Near-Rings

Let N be a right near-ring. Denote by C(N) the multiplicative center of N, and by N _d the set of left-distributive elements of N. In general, C(N) need not be closed under the addition of N. However, the generalized center of N, GC(N) = {a ? N|an _d  = n _d a for all n _d  ? N _d }, is always a subnear-ring of N containing C(N). In this article, we study the problem of determining when C(N) is a subnear-ring of N. We show that, for certain classes of near-rings, C(N) is a subnear-ring of N if and only if C(N) = GC(N). Examples are given to show the limits of the theory.     

Semidirect sum of groups in which endomorphisms are generated by inner automorphisms

An I-E group is a group in which every endomorphism is finitely generated by its inner automorphisms. In this paper a characterization for a semidirect sum of I-E groups to be an I-E group is obtained and some well-known results are generalized. We then use this characterization to prove that a semidirect sum of finite I-E groups will again be an I-E group if the normal semidirect summand is unique and fully invariant. Conditions for a group to be an I-E group are also given.

     

Generalized fuzzy ideals of near-rings

The concept of（∈,∈∨q）-fuzzy subnear-rings（ideals） of a near-ring is introduced and some of its related properties are investigated.In particular,the relationships among ordinary fuzzy subnear-rings（ideals）,（∈,∈∨ q）-fuzzy subnear-rings（ideals） and（∈,∈∨q）-fuzzy subnear-rings（ideals） of near-rings are described.Finally,some characterization of [μ]t is given by means of（∈,∈∨ q）-fuzzy ideals.     

THE MAXIMAL SUBNEAR-RINGS OF THE NEAR-RING OF ZERO-PRESERVING FUNCTIONS ON A FINITE GROUP

In this article for a finite group G, we characterize the maximal subnear-rings of the full near-ring of all zero-preserving functions on G.     

Quasi-e-locally cyclic torsion-free abelian groups

For a torsion-free abelian group , we investigate the problem of determining when is maximal as a ring in the near-ring of all -preserving functions on . We introduce the concept of quasi--locally cyclic groups and determine several properties of these abelian groups.

     

Topological rings,homogeneous functions,and primeness

For any group G such that G is a right R-module for some ring R, the elements of R act on G as endomorphisms and we obtain the near-ring of R-homogeneous maps on G: M_R(G) = {f: G → G|f(ga) = f(g)a for all a ∈ R, g ∈ G}. In the special case that R is a topological ring and G is a topological R-module, we study N_R(G): = {f ∈ M_R(G)|f is continuous}. In particular, we investigate primeness of the near-ring N_R(G) of continuous homogeneous maps on G.     

The augmentation ideal in group near-rings

The definition of the group near-ring R[G] of the near-ring R over the group G as a near-ring of mappings from R ^(G) to itself is due to Le Riche et al. (Arch Math 52:132–139, 1989). In this paper we consider the augmentation ideal Δ of R[G]. If the exponent of G is not 2, then the structure of ΔR ^(G) is determined in terms of commutators and distributors. This is then used to show that Δ is nilpotent if and only if R is weakly distributive, has characteristic p ⁿ for some prime p and G is a finite p-group for the same prime p.      

关于Toeplitz矩阵的某些注记

In this paper,we study real symmetric Toeplitz matrices commutable with tridi-agonal matrices, present more detailed results than those in [1], and extend them to non-symmetric Toeplitz matrices. Also, complex Toeplitz matrices, especially the corresponding matrices of lower order, are discussed.     

某些分块矩阵的逆矩阵

本文研究了某些 3× 3分块矩阵的可逆性条件 ,并给出了可逆时的求逆公式     

矩阵与其友矩阵相似的一个充要条件及其证明

得到一个矩阵A与其特征多项式的友矩阵C相似的充要条件是对应于A的每个不同的特征值λi,Jordan标准形中只含有一个Jordan子矩阵,并给出证明.     

三对角与五对角Toeplitz矩阵求逆的算法

提出了一种求三对角与五对角Toeplitz矩阵逆的快速算法,其思想为先将Toeplitz矩阵扩展为循环矩阵,再快速求循环矩阵的逆,进而运用恰当矩阵分块求原Toeplitz矩阵的逆的算法.算法稳定性较好且复杂度较低.数值例子显示了算法的有效性和稳定性,并指出了算法的适用范围.     

Condition Numbers for Structured Least Squares Problems

This paper studies the normwise perturbation theory for structured least squares problems. The structures under investigation are symmetric, persymmetric, skewsymmetric, Toeplitz and Hankel. We present the condition numbers for structured least squares. AMS subject classification (2000) 15A18, 65F20, 65F25, 65F50