Perturbation of Eigenpairs of Factored Symmetric Tridiagonal Matrices

Suppose that an indefinite symmetric tridiagonal matrix permits triangular factorization T = LDL ^t . We provide individual condition numbers for the eigenvalues and eigenvectors of T when the parameters in L and D suffer small relative perturbations. When there is element growth in the factorization, then some pairs may be robust while others are sensitive. A 4 × 4 example shows the limitations of standard multiplicative perturbation theory and the efficacy of our new condition numbers.     

三对角矩阵的亚正定性

讨论了比三对角矩阵更广泛的一类矩阵的亚正定性,从而给出了三对角矩阵是亚正定矩阵的充分条件.     

三对角对称矩阵逆特征值问题存在唯一解的条件

讨论了利用给定的k(2≤k≤n)个特征对来构造相应的三对角对称矩阵的问题．在求解方法中,将已知的一些关系式等价转化成线性方程组,利用线性方程组的解存在唯一的条件,得到了所研究问题存在唯一解的充要条件,并给出了计算解的数值方法和数值实例．     

由三个特殊次序向量对构造三对角对称矩阵

讨论利用给定的三个特殊次序向量对构造不可约三对角矩阵、Jacobi矩阵和负Jacobi矩阵的反问题.在求解方法中,将已知的一些关系式等价地转化为线性方程组,利用线性方程组有解的条件,得到了所研究问题有惟一解的充要条件,并给出了数值算法和例子.     

Eigenvalues of Symmetric Tridiagonal Matrices: A Fast, Accurate and Reliable Algorithm

An algorithm is developed for obtaining eigenvalues of real,symmetric, tridiagonal matrices. It combines dynamically Given'smethod of bisection and the use of Sturm sequences with variousacceleration devices. A FORTRAN IV computer implementation of the algorithm was usedon ten test matrices found in the literature. The new methodis as precise and reliable as the best published program (Kahan& Varah, 1966), it is never slower, and in at least onecase is two and half times faster than the Kahan and Varah program.     

Fine Spectra of Tridiagonal Toeplitz Matrices

Ukrainian Mathematical Journal - The fine spectra of n-banded triangular Toeplitz matrices and (2n+1)-banded symmetric Toeplitz matrices were computed in (M. Altun, Appl. Math. Comput., 217,...     

Minimum Permanents of Tridiagonal Doubly Stochastic Matrices

We determine the minimum permanents and minimizing matrices of the tridiagonal doubly stochastic matrices and of certain doubly stochastic matrices with prescribed zero entries.     

一类三对角矩阵的特征值和特征向量的研究

讨论了一种三对角矩阵的特征值和特征向量.按矩阵右下角对角元素的参数分为两类,得出特征值和特征向量的结论或数值算法.举例说明了算法的有效性.     

Minimum Permanents of Tridiagonal Doubly Stochastic Matrices

We determine the minimum permanents and minimizing matrices of the tridiagonal doubly stochastic matrices and of certain doubly stochastic matrices with prescribed zero entries.     

三对角矩阵求逆问题的思考——从一道课本习题谈起

矩阵求逆是矩阵代数中的一个重要运算,逆矩阵的获得却困难重重.文中介绍一个三对角形矩阵求逆的新思路,它可以作为求解逆矩阵问题的一个解题模块,学习线性代数课程的一个认知结构,也可以作为教育数学的一个案例.     

判定3,4或5阶对称矩阵偕正性的算法

文献[1]给出了判定阶数不大于5的对称矩阵偕正性的充分必要条件.本文在此基础上,进一步给出了它们严格偕正的条件,并提出了三个算法,它们能够用来有效地判定3,4,5阶对称矩阵严格偕正、偕正或非偕正.     

Decomposition of Matrices into Involutory Matrices and Symmetric Matrices

Let \Omega be a field, and let F denote the Frobenius matrix: $[F = \left( {\begin{array}{*{20}{c}} 0&{ - {\alpha _n}}\{{E_{n - 1}}}&\alpha \end{array}} \right)\]$ where \alpha is an n-1 dimentional vector over Q, and E_n- 1 is identity matrix over \Omega. Theorem 1. There hold two elementary decompositions of Frobenius matrix: (i) F=SJB, where S, J are two symmetric matrices, and B is an involutory matrix; (ii) F=CQD, where O is an involutory matrix, Q is an orthogonal matrix over \Omega, and D is a diagonal matrix. We use the decomposition (i) to deduce the following two theorems: Theorem 2. Every square matrix over \Omega is a product of twe symmetric matrices and one involutory matrix. Theorem 3. Every square matrix over \Omega is a product of not more than four symmetric matrices. By using the decomposition (ii), we easily verify the following Theorem 4(Wonenburger-Djokovic') . The necessary and sufficient condition that a square matrix A may be decomposed as a product of two involutory matrices is that A is nonsingular and similar to its inverse A^-1 over Q (See [2, 3]). We also use the decomosition (ii) to obtain Theorem 5. Every unimodular matrix is similar to the matrix CQB, where C, B are two involutory matrices, and Q is an orthogonal matrix over Q. As a consequence of Theorem 5. we deduce immediately the following Theorem 6 (Gustafson-Halmos-Radjavi). Every unimodular matrix may be decomposed as a product of not more than four involutory matrices (See [1] ). Finally, we use the decomposition (ii) to derive the following Thoerem 7. If the unimodular matrix A possesses one invariant factor which is not constant polynomial, or the determinant of the unimodular matrix A is I and A possesses two invariant factors with the same degree (>0), then A may be decomposed as a product of three involutory matrices. All of the proofs of the above theorems are constructive.     

对称正交反对称矩阵反问题

设P为一给定的对称正交矩阵, 记SAR\+n\-P={A∈R\+\{n×n\}|A\+T=A,(PA)\+T=-PA}. 该文考虑下列问题问题Ⅰ〓给定X∈R\+\{n×m, Λ=diag(λ\-1,λ\-2,…, λ\-m)∈R\+\{m×m\}, 求A∈SAR\+n\-P使AX=XΛ,问题Ⅱ〓给定X,B∈R\+\{n×m, 求A∈SAR\+n\-P使  ‖AX-B‖=min.问题Ⅲ设[AKA～]∈R\+\{n×n\},求A\+*∈S\-E使 ‖[AKA～]-A\+*‖=inf[DD(X]A∈S\-E[DD)]‖[AKA～]-A‖, 其中S\-E为问题Ⅱ的解集合, ‖·‖表示Frobenius范数.该文得到了问题Ⅰ有解的充要条件及解集合的表达式, 给出了解集合S\-E的通式和逼近解A\+*的具体表达式.     

双对称本原矩阵k-点指数的极矩阵

一个n阶本原矩阵A的k-点指数是A的最小幂指数,使得在这个幂中,存在着k个全1行．最近我们得到了n阶双对称本原矩阵的k-点指数的上确界．本文将在此基础上,以伴随图的形式给出其极矩阵的完全刻划．     

The Factorization of Sparse Symmetric Indefinite Matrices

The Harwell multifrontal code MA27 is able to solve symmetricindefinite systems of linear equations such as those that arisefrom least-squares and constrained optimization algorithms,but may sometimes lead to many more arithmetic operations beingneeded to factorize the matrix than is required by other strategies.In this paper, we report on the results of our investigationof this problem. We have concentrated on seeking new strategiesthat preserve the multifrontal principle but follow the sparsitystructure more closely in the case when some of the diagonalentries are zero.     

广义对称矩阵反问题有解的条件

本利用矩阵的奇异值分解讨论了一类广义对矩阵阵反问题，得到了此类矩阵反问题有解的充分必要条件及通解的表达式。     

Symmetric Weighing Matrices Constructed using Group Matrices

A weighing matrix of order n and weight m² is a square matrix M of order n with entries from {-1,0,+1} such that MM^T=m²I where I is the identity matrix of order n. If M is a group matrix constructed using a group of order n, M is called a group weighing matrix. Recently, group weighing matrices were studied intensively, especially when the groups are cyclic and abelian. In this paper, we study the abelian group weighing matrices that are symmetric, i.e.M^T=M. Some new examples are found. Also we obtain a few exponent bounds on abelian groups that admit symmetric group weighing matrices. In particular, we prove that there is no symmetric abelian group weighing matrices of order 2p^r and weight p² where p is a prime and p≥ 5.Communicated by: K.T. Arasu     

双对称本原矩阵κ-点指数的极矩阵

一个n阶本原矩阵A的κ-点指数是A的最小幂指数,使得在这个幂中,存在着κ个全1行.最近我们得到了n阶双对称本原矩阵的κ-点指数的上确界.本文将在此基础上,以伴随图的形式给出其极矩阵的完全刻划.