平方非正的符号矩阵的平方中负元个数

本文给出了一个符号矩阵A当A^2非正时A^2中负元个数N－(A^2)的上,下界,并确定相应的极矩阵。     

三幂等符号模式矩阵的结构

Abstract. A matrix whose entries are , -, and 0 is called a sign pattern matrix. For a signpattern matrix A,if A3 =A, then A is said to be sign tripotent. In this paper, the characteriza-tion of the n by n(n≥2) sign pattern matrices A which are sign tripotent has been given out.Furthermore, the necessary and sufficient condition of A3=A but A2≠A is obtained, too.     

非负广义幂等矩阵

非负幂等矩阵在［１］中已有详细地讨论和重要地应用。［２］给出了Ａ≥０，Ａｋ＋１＝Ａ，ｋ是正整数，Ａｋ是零对称幂等矩阵的充要条件。本文给出了一般非负广义幂等矩阵的充要条件。并讨论了广义幂等矩阵的秩与其广义幂等指数的关系，推广了［２］中的部分结论。     

立方非负的不可约符号模式

以 ，-，0为元素的矩阵称为符号模式矩阵．本文考虑符号模式矩阵的立方模式，给出了至少含一个负元的不可约符号模式的立方模式是非负的充要条件及在置换相似下的标准型；得到了立方非负的符号模式矩阵中出现的正元素的个数的最大(小)值及给出了达到这些最大(小)值的不可约符号模式矩阵的完整刻画．     

迹非零的布尔矩阵的幂敛指数

本文证明ｄ个正对角元的ｎ阶布尔方阵（１≤ｄ＜ｎ／２）幂敛指数有上界（ｎ－ｄ－１）＾２＋１，ｎ＞４，并给出了幂敛指数达到此上界的这类方阵的完全刻画，由此，即得ｎ阶非零迹布尔方阵幂敛指数的最大值为（ｎ－２）＾２＋１。     

分块幂等矩阵中广义Schur补的幂等性

为了讨论分块幂等矩阵中使用A(1)与A(2)的广义Schur补的幂等性问题,定义了(M/D)I=D-CA(1)B和(M/A)_O=D-CA(2)B,讨论得到了(M/D)_I=D-CA(1)B与(M/A)O=D-CA(2)B具有幂等性的充要条件,并研究了一些特殊情况,推广了J K Baksalary和Zhou J H的结论.     

布尔矩阵的幂敛指数集

给出了不含非零对角元的ｎ阶布尔矩阵的幂敛指数集的明显表达式,从而完全解决了布尔矩阵依赖于非零对角元个数的幂敛指数集的刻画问题。     

恰有d个正对角元的布尔矩阵的幂敛指数的分布

设Bn为n阶布尔矩阵的集合,Dn(d)=｛A∈Bn|A中恰有d个正对角元,本文完全确定了矩阵类Dn（d）的幂敛指数集kn（d）．     

幂零矩阵的m次根

主要研究当A是幂零矩阵时,方程Xm=A的性质.我们可以得到一些关于方程Xm=A无解性与A自身的特点之间的关系.     

恰有t行含s圈正元的布尔矩阵幂敛指数的估计

设D_n,s(t)是恰有t行含s圈正元的n阶布尔矩阵的集合,本文得到了当s为素数时D_n,s(t)中矩阵的幂敛指数的一个新上界。     

On Ranks of Matrices Associated with Trees

A sign pattern matrix is a matrix whose entries are from the set {+,–,0}. The purpose of this paper is to obtain bounds on the minimum rank of any symmetric sign pattern matrix A whose graph is a tree T (possibly with loops). In the special case when A is nonnegative with positive diagonal and the graph of A is star-like, the exact value of the minimum rank of A is obtained. As a result, it is shown that the gap between the symmetric minimal and maximal ranks can be arbitrarily large for a symmetric tree sign pattern A. Supported by NSF grant No. DMS-00700AMS classification: 05C50, 05C05, 15A48     

The Number of Negative Entries in a Sign Pattern Allowing Orthogonality

A ± sign pattern is a matrix whose entries are in the set {+,–}. An n×n ± sign pattern A allows orthogonality if there exists a real orthogonal matrix B in the qualitative class of A. In this paper, we prove that for n3 there is an n×n ± sign pattern A allowing orthogonality with exactly k negative entries if and only if n–1kn²–n+1.Research supported by Shanxi Natural Science Foundation 20011006, 20041010Final version received: October 22, 2003     

Alternating Sign Matrices and Some Deformations of Weyl's Denominator Formulas

An alternating sign matrix is a square matrix whose entries are 1, 0, or –1, and which satisfies certain conditions. Permutation matrices are alternating sign matrices. In this paper, we use the (generalized) Littlewood's formulas to expand the products and 2 as sums indexed by sets of alternating sign matrices invariant under a 180° rotation. If we put t = 1, these expansion formulas reduce to the Weyl's denominator formulas for the root systems of type B _n and C _n. A similar deformation of the denominator formula for type D _n is also given.     

非负对称符号模式的惯量集(英文)

For a symmetric sign pattern S1 the inertia set of S is defined to be the set of all ordered triples si（S） = {i（A） ： A = A^T ∈ Q（S）} Consider the n × n sign pattern Sn, where Sn is the pattern with zero entry （i,j） for 1 ≤ i = j ≤ n or｜i -j｜=n- 1 and positive entry otherwise. In this paper, it is proved that si（Sn） = {（n1, n2, n - n1 - n2）｜n1≥ 1 and n2 ≥ 2} for n ≥ 4.     

Primitive non-powerful sign pattern matrices with base 2

A sign pattern matrix M with zero trace is primitive non-powerful if for some positive integer k, M ^k ?=?J _#. The base l(M) of the primitive non-powerful matrix M is the smallest integer k. By considering the signed digraph S whose adjacent matrix is the primitive non-powerful matrix M, we will show that if l(M)?=?2, the minimum number of non-zero entries of M is 5n???8 or 5n???7 depending on whether n is even or odd.     

谱任意的符号模式矩阵

一个n阶符号模式矩阵A称为是谱任意的,如果对任意的实系数n次首1多项式r(x),在A的定性矩阵类Q(A)中至少存在一个实矩阵B,使得B的特征多项式是r(x),文中证明了当n为奇数时n阶谱任意符号模式矩阵是存在的。     

Sign patterns occurring in orthogonal matrices

Which sign patterns occur among orthogonal matrices? The first examples of ± sign patterns that meet the obvious necessary conditions on pairs of rows and columns but do not allow an orthogonal matrix are given. They are essentially the only examples for the 6-by-6 matrices and there are no smaller examples. Two new broad necessary conditions are given for the problem of orthogonal sign patterns. Both generalize the obvious conditions in a certain way and are the first new necessary conditions in the 30 +year history of the problem.