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A note on the boundary of the Birkhoff-James ε-orthogonality sets 关于Birkhoff-James ε-正交集边界的一个注记
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2022-01-12 DOI: 10.13001/ela.2022.6561
Georgios Katsouleas, Vasiliki Panagakou, P. Psarrakos
The Birkhoff-James $varepsilon$-sets of vectors and vector-valued polynomials (in one complex variable) have recently been introduced as natural generalizations of the standard numerical range of (square) matrices or operators and matrix or operator polynomials, respectively. Corners on the boundary curves of these sets are of particular interest, not least because of their importance in visualizing these sets. In this paper, we provide a characterization for the corners of the Birkhoff-James $varepsilon$-sets of vectors and vector-valued polynomials, completing and expanding upon previous exploration of the geometric propertiesof these sets. We also propose a randomized algorithm for approximating their boundaries.
Birkhoff James$varepsilon$-向量集和向量值多项式(在一个复变量中)最近分别被引入为(平方)矩阵或算子以及矩阵或算子多项式的标准数值范围的自然推广。这些集合的边界曲线上的角点特别令人感兴趣,尤其是因为它们在可视化这些集合时很重要。在本文中,我们提供了向量和向量值多项式的Birkhoff James$varepsilon$-集的角的刻画,完成并扩展了先前对这些集的几何性质的探索。我们还提出了一种随机算法来逼近它们的边界。
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引用次数: 0
Real dimension of the Lie algebra of S-skew-Hermitian matrices S-偏序矩阵李代数的实维数
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2022-01-07 DOI: 10.13001/ela.2022.5443
Jonathan Caalim, Yuuji Tanaka
Let $M_n(mathbb{C})$ be the set of $ntimes n$ matrices over the complex numbers. Let $S in M_n(mathbb{C})$. A matrix $Ain M_n(mathbb{C})$ is said to be $S$-skew-Hermitian if $SA^*=-AS$ where $A^*$ is the conjugate transpose of $A$. The set $mathfrak{u}_S$ of all $S$-skew-Hermitian matrices is a Lie algebra. In this paper, we give a real dimension formula for $mathfrak{u}_S$ using the Jordan block decomposition of the cosquare $S(S^*)^{-1}$ of $S$ when $S$ is nonsingular.
设$M_n(mathbb{C})$是在复数上的$n乘以n$矩阵的集合。让$S in M_n(mathbb{C})$。一个矩阵$Ain M_n(mathbb{C})$被称为$S$-斜厄米矩阵,如果$SA^*=-AS$,其中$A^*$是$A$的共轭转置。所有$S$-斜厄米矩阵的集合$mathfrak{u}_S$是一个李代数。本文利用$S$的余方$S(S^*)^{-1}$的Jordan块分解,给出了$S$非奇异时$mathfrak{u}_S$的实维公式。
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引用次数: 0
Compatibility and companions for Leonard pairs Leonard配对的兼容性和同伴
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2021-12-26 DOI: 10.13001/ela.2022.6861
K. Nomura, Paul M. Terwilliger
In this paper, we introduce the concepts of compatibility and companion for Leonard pairs. These concepts are roughly described as follows. Let $mathbb{F}$ denote a field, and let $V$ denote a vector space over $mathbb{F}$ with finite positive dimension.A Leonard pair on $V$ is an ordered pair of diagonalizable $mathbb{F}$-linear maps $A : V to V$ and $A^* : V to V$ that each act in an irreducible tridiagonal fashion on an eigenbasis for the other one. Leonard pairs $A,A^*$ and $B,B^*$ on $V$ are said to be compatible whenever $A^* = B^*$ and $[A,A^*] = [B,B^*]$, where $[r,s] = r s - s r$. For a Leonard pair $A,A^*$ on $V$, by a companion of $A,A^*$ we mean an $mathbb{F}$-linear map $K: V to V$ such that $K$ is a polynomial in $A^*$ and $A-K, A^*$ is a Leonard pair on $V$. The concepts of compatibility and companion are related as follows. For compatible Leonard pairs $A,A^*$ and $B,B^*$ on $V$, define $K = A-B$. Then $K$ is a companion of $A,A^*$. For a Leonard pair $A,A^*$ on $V$ and a companion $K$ of $A,A^*$,define $B = A-K$ and $B^* = A^*$. Then $B,B^*$ is a Leonard pair on $V$ that is compatible with $A,A^*$. Let $A,A^*$ denote a Leonard pair on $V$. We find all the Leonard pairs $B, B^*$ on $V$ that are compatible with $A,A^*$.For each solution $B, B^*$, we describe the corresponding companion $K = A-B$.
本文引入了伦纳德对的相容性和伴生的概念。这些概念大致描述如下。设$mathbb{F}$表示一个域,设$V$表示$mathbb{F}$上一个有限正维的向量空间。$V$上的伦纳德对是$mathbb{F}$的可对角线性映射$A: V 到V$和$A^*: V 到V$的有序对,它们在另一个的特征基上以不可约的三对角方式作用。当$A^* = B^*$和$[A,A^*] = [B,B^*]$时,$V$上的$A,A^*$和$B,B^*$被认为是兼容的,其中$[r,s] = rs - s r$。对于$V$上的伦纳德对$ a, a ^*$,通过$ a, a ^*$的伴星我们指$mathbb{F}$-线性映射$K: V$,使得$K$是$ a ^*$和$ a -K, a ^*$是$V$上的伦纳德对。兼容性和伴侣的概念相关如下。对于$V$上的兼容伦纳德对$A,A^*$和$B,B^*$,定义$K = A-B$。那么$K$是$ a的伴星,a ^*$。对于$V$上的伦纳德对$ a, a ^*$和$ a, a ^*$的伴生$K$,定义$B = a -K$和$B^* = a ^*$。则$B,B^*$是$V$上与$ a, a ^*$兼容的伦纳德对。设$A,A^*$表示$V$上的伦纳德对。我们在$V$上找到与$A,A^*$相容的所有伦纳德对$B, B^*$。对于每个解$B, B^*$,我们描述对应的伴解$K = A-B$。
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引用次数: 1
The algebra generated by nilpotent elements in a matrix centralizer 矩阵中心化子中幂零元生成的代数
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2021-12-23 DOI: 10.13001/ela.2022.6503
Ralph John de la Cruz, Eloise Misa
For an arbitrary square matrix $S$, denote by $C(S)$ the centralizer of $S$, and by $C(S)_N$ the set of all nilpotent elements in $C(S)$. In this paper, we use the Weyr canonical form to study the subalgebra of $C(S)$ generated by $C(S)_N$. We determine conditions on $S$ such that $C(S)_N$ is a subalgebra of $C(S)$. We also determine conditions on $S$ such that the subalgebra generated by $C(S)_N$ is $C(S).$
对于任意的平方矩阵$S$,用$C(S)$表示$S$的中心化子,用$C(S)_N$表示$C(S)$中所有幂零元素的集合。在本文中,我们使用Weyr正则形式来研究由$C(S)_N$生成的$C(S)$的子代数。我们确定了$S$上的条件,使得$C(S)_N$是$C(S)$的子代数。我们还确定了$S$上的条件,使得由$C(S)_N$生成的子代数是$C(S)$
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引用次数: 2
A note on commuting additive maps on rank k symmetric matrices 关于k阶对称矩阵上可交换加性映射的注释
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2021-12-22 DOI: 10.13001/ela.2021.6349
W. L. Chooi, Yean Nee Tan
Let $ngeq 2$ and $11$ and the underlying field $mathbb{F}$ of characteristic not two are included.
设包含特征不二的$ngeq 2$和$11$以及底层字段$mathbb{F}$。
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引用次数: 0
Inertia Sets of Semicliqued Graphs 半液化图的惯性集
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2021-12-22 DOI: 10.13001/ela.2021.4933
A. Yielding, Taylor Hunt, Joel Jacobs, Jazmine Juarez, Taylor Rhoton, Heath Sell
In this paper, we investigate inertia sets of simple connected undirected graphs. The main focus is on the shape of their corresponding inertia tables, in particular whether or not they are trapezoidal. This paper introduces a special family of graphs created from any given graph, $G$, coined semicliqued graphs and denoted $widetilde{K}G$. We establish the minimum rank and inertia sets of some $widetilde{K}G$ in relation to the original graph $G$. For special classes of graphs, $G$, it can be shown that the inertia set of $G$ is a subset of the inertia set of $widetilde{K}G$. We provide the inertia sets for semicliqued cycles, paths, stars, complete graphs, and for a class of trees. In addition, we establish an inertia set bound for semicliqued complete bipartite graphs.
本文研究了简单连通无向图的惯性集。主要关注的是它们对应的惯性表的形状,特别是它们是否为梯形。本文介绍了由任意给定图$G$生成的一类特殊图$G$,即半液化图,记为$ widdetilde {K}G$。我们建立了关于原始图$G$的最小秩集和最小惯性集。对于图的特殊类$G$,可以证明$G$的惯性集是$ widdetilde {K}G$的惯性集的一个子集。给出了半液化环、路径、星形、完全图和一类树的惯性集。此外,我们建立了半液化完全二部图的惯性集界。
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引用次数: 0
Expressions and characterizations for the Moore-Penrose inverse of operators and matrices 算子和矩阵的Moore-Penrose逆的表达式和表征
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2021-12-20 DOI: 10.13001/ela.2023.7315
P. Morillas
Under certain conditions, we prove that the Moore-Penrose inverse of a sum of operators is the sum of the Moore-Penrose inverses. From this, we derive expressions and characterizations for the Moore-Penrose inverse of an operator that are useful for its computation. We give formulations of them for finite matrices and study the Moore-Penrose inverse of circulant matrices and of distance matrices of certain graphs.
在一定条件下,我们证明了算子和的Moore-Penrose逆是Moore-Pennrose逆的和。由此,我们导出了对算子的Moore-Penrose逆的计算有用的表达式和特征。我们给出了有限矩阵的它们的公式,并研究了某些图的循环矩阵和距离矩阵的Moore-Penrose逆。
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引用次数: 1
On $m$-th roots of nilpotent matrices 关于幂零矩阵的$m$-根
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2021-12-14 DOI: 10.13001/ela.2021.6331
Semra Ozturk
A new necessary and sufficient condition for the existence of an $m$-th root of a nilpotent matrix in terms of the multiplicities of Jordan blocks is obtained and expressed as a system of linear equations with nonnegative integer entries which is suitable for computer programming. Thus, computation of the Jordan form of the $m$-th power of a nilpotent matrix is reduced to a single matrix multiplication; conversely, the existence of an $m$-th root of a nilpotent matrix is reduced to the existence of a nonnegative integer solution to the corresponding system of linear equations. Further, an erroneous result in the literature on the total number of Jordan blocks of a nilpotent matrix having an $m$-th root is corrected and generalized. Moreover, for a singular matrix having an $m$-th root with a pair of nilpotent Jordan blocks of sizes $s$ and $l$, a new $m$-th root is constructed by replacing that pair by another one of sizes $s+i$ and $l-i$, for special $s,l,i$. This method applies to solutions of a system of linear equations having a special matrix of coefficients. In addition, for a matrix $A$ over an arbitrary field that is a sum of two commuting matrices, several results for the existence of $m$-th roots of $A^k$ are obtained.
得到了幂零矩阵第$m$-根存在于Jordan块的乘性方面的一个新的充要条件,并将其表示为一个适用于计算机编程的非负整数项线性方程组。因此,幂零矩阵$m$-次幂的Jordan形式的计算被简化为单矩阵乘法;相反,幂零矩阵的第$m$-根的存在性被简化为相应线性方程组的非负整数解的存在性。此外,对文献中关于具有第$m$-根的幂零矩阵的Jordan块总数的一个错误结果进行了纠正和推广。此外,对于具有第$m$-个根的奇异矩阵和一对大小为$s$和$l$的幂零Jordan块,通过用另一个大小为$s+i$和$l-i$的块替换该对来构造新的第$m$个根,对于特殊的$s,l,i$。这种方法适用于具有特殊系数矩阵的线性方程组的解。此外,对于任意域上的矩阵$a$,它是两个交换矩阵的和,得到了$a^k$的$m$根存在的几个结果。
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引用次数: 0
On the Gerv{s}gorin disks of distance matrices of graphs 图的距离矩阵的Gerv{s}gorin盘
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2021-12-08 DOI: 10.13001/ela.2021.6489
M. Aouchiche, B. Rather, Issmail El Hallaoui
For a simple connected graph $G$, let $D(G)$, $Tr(G)$, $D^{L}(G)=Tr(G)-D(G)$, and $D^{Q}(G)=Tr(G)+D(G)$ be the distance matrix, the diagonal matrix of the vertex transmissions, the distance Laplacian matrix, and the distance signless Laplacian matrix of $G$, respectively. Atik and Panigrahi [2] suggested the study of the problem: Whether all eigenvalues, except the spectral radius, of $ D(G) $ and $ D^{Q}(G) $ lie in the smallest Gerv{s}gorin disk? In this paper, we provide a negative answer by constructing an infinite family of counterexamples.
对于简单连通图$G$,设$D(G)$、$Tr(G)$、$D^{L}(G)=Tr(G)-D(G)$和$D^{Q}(G)=Tr(G)+D(G)$分别为$G$的距离矩阵、顶点传递的对角矩阵、距离拉普拉斯矩阵和距离无符号拉普拉斯矩阵。Atik和Panigrahi[2]提出了一个问题的研究:$ D(G) $和$ D^{Q}(G) $的所有特征值,除了谱半径,是否都在最小的Gerv{s}gorin圆盘上?在本文中,我们通过构造一个无穷反例族来给出一个否定的答案。
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引用次数: 1
Families of graphs with twin pendent paths and the Braess edge 具有双悬垂路径和Braess边的图族
IF 0.7 4区 数学 Q2 Mathematics Pub Date : 2021-12-07 DOI: 10.13001/ela.2022.5913
Sooyeon Kim
In the context of a random walk on an undirected graph, Kemeny's constant can measure the average travel time for a random walk between two randomly chosen vertices. We are interested in graphs that behave counter-intuitively in regard to Kemeny's constant: in particular, we examine graphs with a cut-vertex at which at least two branches are paths, regarding whether the insertion of a particular edge into a graph results in an increase of Kemeny's constant. We provide several tools for identifying such an edge in a family of graphs and for analysing asymptotic behaviour of the family regarding the tendency to have that edge; and classes of particular graphs are given as examples. Furthermore, asymptotic behaviours of families of trees are described.
在无向图上随机行走的情况下,Kemeny常数可以测量两个随机选择的顶点之间随机行走的平均行进时间。我们对在Kemeny常数方面表现得与直觉相反的图感兴趣:特别是,我们研究具有至少两个分支是路径的割顶点的图,关于将特定边插入图中是否会导致Kemeny常量的增加。我们提供了几种工具来识别图族中的这种边,并分析该族关于具有该边的趋势的渐近行为;并给出了特定图的类作为例子。此外,还描述了树族的渐近行为。
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引用次数: 4
期刊
Electronic Journal of Linear Algebra
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