Pub Date : 2024-07-17DOI: 10.1016/j.laa.2024.07.013
By employing a weighted Frobenius norm with a positive definite matrix ω, we introduce natural generalizations of the famous Böttcher-Wenzel (BW) inequality. Based on the combination of the weighted Frobenius norm and the standard Frobenius norm , there are exactly five possible generalizations, labeled (i) through (v), for the bounds on the norms of the commutator . In this paper, we establish the tight bounds for cases (iii) and (v), and propose conjectures regarding the tight bounds for cases (i) and (ii). Additionally, the tight bound for case (iv) is derived as a corollary of case (i). All these bounds (i)-(v) serve as generalizations of the BW inequality. The conjectured bounds for cases (i) and (ii) (and thus also (iv)) are numerically supported for matrices up to size . Proofs are provided for and certain special cases. Interestingly, we find applications of these bounds in quantum physics, particularly in the contexts of the uncertainty relation and open quantum dynamics.
{"title":"Böttcher-Wenzel inequality for weighted Frobenius norms and its application to quantum physics","authors":"","doi":"10.1016/j.laa.2024.07.013","DOIUrl":"10.1016/j.laa.2024.07.013","url":null,"abstract":"<div><p>By employing a weighted Frobenius norm with a positive definite matrix <em>ω</em>, we introduce natural generalizations of the famous Böttcher-Wenzel (BW) inequality. Based on the combination of the weighted Frobenius norm <figure><img></figure> and the standard Frobenius norm <figure><img></figure>, there are exactly five possible generalizations, labeled (i) through (v), for the bounds on the norms of the commutator <span><math><mo>[</mo><mi>A</mi><mo>,</mo><mi>B</mi><mo>]</mo><mo>:</mo><mo>=</mo><mi>A</mi><mi>B</mi><mo>−</mo><mi>B</mi><mi>A</mi></math></span>. In this paper, we establish the tight bounds for cases (iii) and (v), and propose conjectures regarding the tight bounds for cases (i) and (ii). Additionally, the tight bound for case (iv) is derived as a corollary of case (i). All these bounds (i)-(v) serve as generalizations of the BW inequality. The conjectured bounds for cases (i) and (ii) (and thus also (iv)) are numerically supported for matrices up to size <span><math><mi>n</mi><mo>=</mo><mn>15</mn></math></span>. Proofs are provided for <span><math><mi>n</mi><mo>=</mo><mn>2</mn></math></span> and certain special cases. Interestingly, we find applications of these bounds in quantum physics, particularly in the contexts of the uncertainty relation and open quantum dynamics.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141872807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-15DOI: 10.1016/j.laa.2024.07.007
Given a pair of real symmetric matrices with nonzero patterns determined by the edges of any pair of chosen graphs on n vertices, we consider an inverse eigenvalue problem for the structured matrix . We conjecture that C can attain any spectrum that is closed under conjugation. We use a structured Jacobian method to prove this conjecture for A and B of orders at most 4 or when the graph of A has a Hamilton path, and prove a weaker version of this conjecture for any pair of graphs with a restriction on the multiplicities of eigenvalues of C.
给定一对实对称矩阵 A,B∈Rn×n,其非零图案由 n 个顶点上任意一对所选图形的边决定,我们考虑结构矩阵 C=[ABIO]∈R2n×2n的逆特征值问题。我们猜想,C 可以达到任何在共轭作用下封闭的谱。我们使用结构雅各布方法证明了阶最多为 4 或当 A 的图有一条汉密尔顿路径时的 A 和 B 的这一猜想,并证明了对 C 的特征值乘数有限制的任何一对图的这一猜想的较弱版本。
{"title":"An inverse eigenvalue problem for structured matrices determined by graph pairs","authors":"","doi":"10.1016/j.laa.2024.07.007","DOIUrl":"10.1016/j.laa.2024.07.007","url":null,"abstract":"<div><p>Given a pair of real symmetric matrices <span><math><mi>A</mi><mo>,</mo><mi>B</mi><mo>∈</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi><mo>×</mo><mi>n</mi></mrow></msup></math></span> with nonzero patterns determined by the edges of any pair of chosen graphs on <em>n</em> vertices, we consider an inverse eigenvalue problem for the structured matrix <span><math><mi>C</mi><mo>=</mo><mrow><mo>[</mo><mtable><mtr><mtd><mspace></mspace><mi>A</mi><mspace></mspace></mtd><mtd><mi>B</mi></mtd></mtr><mtr><mtd><mspace></mspace><mi>I</mi><mspace></mspace></mtd><mtd><mi>O</mi></mtd></mtr></mtable><mo>]</mo></mrow><mo>∈</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn><mi>n</mi><mo>×</mo><mn>2</mn><mi>n</mi></mrow></msup></math></span>. We conjecture that <em>C</em> can attain any spectrum that is closed under conjugation. We use a structured Jacobian method to prove this conjecture for <em>A</em> and <em>B</em> of orders at most 4 or when the graph of <em>A</em> has a Hamilton path, and prove a weaker version of this conjecture for any pair of graphs with a restriction on the multiplicities of eigenvalues of <em>C</em>.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0024379524002970/pdfft?md5=fa415a9b3c87c51014076976d43924d1&pid=1-s2.0-S0024379524002970-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141710709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-14DOI: 10.1016/j.laa.2024.07.006
A complex unit gain graph, or -gain graph, is a triple comprised of a simple graph G as the underlying graph of Φ, the set of unit complex numbers , and a gain function with the property that . A cactus graph is a connected graph in which any two cycles have at most one vertex in common.
In this paper, we firstly show that there does not exist a complex unit gain graph with nullity , where , and are the order, matching number, and cyclomatic number of G. Next, we provide a lower bound on the nullity for connected complex unit gain graphs and an upper bound on the nullity for complex unit gain bipartite graphs. Finally, we characterize all non-singular complex unit gain bipartite cactus graphs, which generalizes a result in Wong et al. (2022) [30].
复数单位增益图或 T 增益图是一个三元组 Φ=(G,T,φ),由作为 Φ 底图的简单图 G、单位复数集合 T={z∈C:|z|=1} 和增益函数 φ:E→→T 组成,其性质为 φ(eij)=φ(eji)-1 。本文首先证明不存在空性为 n(G)-2m(G)+2c(G)-1(其中 n(G)、m(G)和 c(G) 分别为 G 的阶、匹配数和循环数)的复数单位增益图。最后,我们描述了所有非星状复数单位增益双方形仙人掌图的特征,这概括了 Wong 等人(2022)[30] 的一个结果。
{"title":"Bounds of nullity for complex unit gain graphs","authors":"","doi":"10.1016/j.laa.2024.07.006","DOIUrl":"10.1016/j.laa.2024.07.006","url":null,"abstract":"<div><p>A complex unit gain graph, or <span><math><mi>T</mi></math></span>-gain graph, is a triple <span><math><mi>Φ</mi><mo>=</mo><mo>(</mo><mi>G</mi><mo>,</mo><mi>T</mi><mo>,</mo><mi>φ</mi><mo>)</mo></math></span> comprised of a simple graph <em>G</em> as the underlying graph of Φ, the set of unit complex numbers <span><math><mi>T</mi><mo>=</mo><mo>{</mo><mi>z</mi><mo>∈</mo><mi>C</mi><mo>:</mo><mo>|</mo><mi>z</mi><mo>|</mo><mo>=</mo><mn>1</mn><mo>}</mo></math></span>, and a gain function <span><math><mi>φ</mi><mo>:</mo><mover><mrow><mi>E</mi></mrow><mrow><mo>→</mo></mrow></mover><mo>→</mo><mi>T</mi></math></span> with the property that <span><math><mi>φ</mi><mo>(</mo><msub><mrow><mi>e</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub><mo>)</mo><mo>=</mo><mi>φ</mi><msup><mrow><mo>(</mo><msub><mrow><mi>e</mi></mrow><mrow><mi>j</mi><mi>i</mi></mrow></msub><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>. A cactus graph is a connected graph in which any two cycles have at most one vertex in common.</p><p>In this paper, we firstly show that there does not exist a complex unit gain graph with nullity <span><math><mi>n</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>−</mo><mn>2</mn><mi>m</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>+</mo><mn>2</mn><mi>c</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>−</mo><mn>1</mn></math></span>, where <span><math><mi>n</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span>, <span><math><mi>m</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> and <span><math><mi>c</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> are the order, matching number, and cyclomatic number of <em>G</em>. Next, we provide a lower bound on the nullity for connected complex unit gain graphs and an upper bound on the nullity for complex unit gain bipartite graphs. Finally, we characterize all non-singular complex unit gain bipartite cactus graphs, which generalizes a result in Wong et al. (2022) <span><span>[30]</span></span>.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141701119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-14DOI: 10.1016/j.laa.2024.07.008
In this article, taking a Fiedler's result on the spectrum of a matrix formed from two symmetric matrices as a motivation, we deduce a more general result on the eigenvalues of a matrix, which form from n symmetric matrices. As an important application, we obtain the adjacency spectra, Laplacian spectra and signless Laplacian spectra of a graph with a particular almost equitable partition.
本文以费德勒关于由两个对称矩阵形成的矩阵谱的结果为动机,推导出关于由 n 个对称矩阵形成的矩阵特征值的更一般的结果。作为一个重要的应用,我们得到了具有特定几乎等分的图的邻接谱、拉普拉斯谱和无符号拉普拉斯谱。
{"title":"A generalization of Fiedler's lemma and its applications","authors":"","doi":"10.1016/j.laa.2024.07.008","DOIUrl":"10.1016/j.laa.2024.07.008","url":null,"abstract":"<div><p>In this article, taking a Fiedler's result on the spectrum of a matrix formed from two symmetric matrices as a motivation, we deduce a more general result on the eigenvalues of a matrix, which form from <em>n</em> symmetric matrices. As an important application, we obtain the adjacency spectra, Laplacian spectra and signless Laplacian spectra of a graph with a particular almost equitable partition.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141696804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-11DOI: 10.1016/j.laa.2024.07.005
We establish necessary and sufficient conditions for invertibility of symmetric three-by-three block matrices having a double saddle-point structure that guarantee the unique solvability of double saddle-point systems. We consider various scenarios, including the case where all diagonal blocks are allowed to be rank deficient. Under certain conditions related to the nullity of the blocks and intersections of their kernels, an explicit formula for the inverse is derived.
{"title":"On the invertibility of matrices with a double saddle-point structure","authors":"","doi":"10.1016/j.laa.2024.07.005","DOIUrl":"10.1016/j.laa.2024.07.005","url":null,"abstract":"<div><p>We establish necessary and sufficient conditions for invertibility of symmetric three-by-three block matrices having a double saddle-point structure that guarantee the unique solvability of double saddle-point systems. We consider various scenarios, including the case where all diagonal blocks are allowed to be rank deficient. Under certain conditions related to the nullity of the blocks and intersections of their kernels, an explicit formula for the inverse is derived.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0024379524002957/pdfft?md5=2f9745e86feef3ccac116a6ac9360448&pid=1-s2.0-S0024379524002957-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141720123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1016/j.laa.2024.07.004
In this paper, we solve a classical counting problem for non-degenerate forms of symplectic and hermitian type defined on a vector space: given a subspace π, we find the number of non-singular subspaces that are trivially intersecting with π and span a non-singular subspace with π. Lower bounds for the quantity of such pairs where π is non-singular were first studied in “Glasby, Niemeyer, Praeger (Finite Fields Appl., 2022)”, which was later improved in “Glasby, Ihringer, Mattheus (Des. Codes Cryptogr., 2023)” and generalised in “Glasby, Niemeyer, Praeger (Linear Algebra Appl., 2022)”. In this paper, we derive explicit formulae, which allow us to give the exact proportion and improve the known lower bounds.
{"title":"Anzahl theorems for trivially intersecting subspaces generating a non-singular subspace I: Symplectic and hermitian forms","authors":"","doi":"10.1016/j.laa.2024.07.004","DOIUrl":"10.1016/j.laa.2024.07.004","url":null,"abstract":"<div><p>In this paper, we solve a classical counting problem for non-degenerate forms of symplectic and hermitian type defined on a vector space: given a subspace <em>π</em>, we find the number of non-singular subspaces that are trivially intersecting with <em>π</em> and span a non-singular subspace with <em>π</em>. Lower bounds for the quantity of such pairs where <em>π</em> is non-singular were first studied in “Glasby, Niemeyer, Praeger (Finite Fields Appl., 2022)”, which was later improved in “Glasby, Ihringer, Mattheus (Des. Codes Cryptogr., 2023)” and generalised in “Glasby, Niemeyer, Praeger (Linear Algebra Appl., 2022)”. In this paper, we derive explicit formulae, which allow us to give the exact proportion and improve the known lower bounds.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141694473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-06DOI: 10.1016/j.laa.2024.06.028
In this paper, we study the representation of an infinite-dimensional Lie algebra related to the q-analog Virasoro-like Lie algebra. We give the necessary and sufficient conditions for the highest weight irreducible module of to be a Harish-Chandra module. We prove that the Verma -module is either irreducible or has the corresponding irreducible highest weight -module that is a Harish-Chandra module. We also give the maximal proper submodule of the Verma module and the e-character of the irreducible highest weight -module when the highest weight ϕ satisfies some natural conditions. Furthermore, we give the classification of the Harish-Chandra -modules with nontrivial central charge.
{"title":"Representations of the C-series related to the q-analog Virasoro-like Lie algebra","authors":"","doi":"10.1016/j.laa.2024.06.028","DOIUrl":"10.1016/j.laa.2024.06.028","url":null,"abstract":"<div><p>In this paper, we study the representation of an infinite-dimensional Lie algebra <span><math><mi>C</mi></math></span> related to the q-analog Virasoro-like Lie algebra. We give the necessary and sufficient conditions for the highest weight irreducible module <span><math><mi>V</mi><mo>(</mo><mi>ϕ</mi><mo>)</mo></math></span> of <span><math><mi>C</mi></math></span> to be a Harish-Chandra module. We prove that the Verma <span><math><mi>C</mi></math></span>-module <span><math><mover><mrow><mi>V</mi></mrow><mrow><mo>¯</mo></mrow></mover><mo>(</mo><mi>ϕ</mi><mo>)</mo></math></span> is either irreducible or has the corresponding irreducible highest weight <span><math><mi>C</mi></math></span>-module <span><math><mi>V</mi><mo>(</mo><mi>ϕ</mi><mo>)</mo></math></span> that is a Harish-Chandra module. We also give the maximal proper submodule of the Verma module <span><math><mover><mrow><mi>V</mi></mrow><mrow><mo>¯</mo></mrow></mover><mo>(</mo><mi>ϕ</mi><mo>)</mo></math></span> and the <em>e</em>-character of the irreducible highest weight <span><math><mi>C</mi></math></span>-module <span><math><mi>V</mi><mo>(</mo><mi>ϕ</mi><mo>)</mo></math></span> when the highest weight <em>ϕ</em> satisfies some natural conditions. Furthermore, we give the classification of the Harish-Chandra <span><math><mi>C</mi></math></span>-modules with nontrivial central charge.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141588541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-06DOI: 10.1016/j.laa.2024.07.001
Nicola Guglielmi, Stefano Sicilia
Spectral clustering is a well-known technique which identifies clusters in an undirected graph, with vertices and weight matrix , by exploiting its graph Laplacian . In particular, the clusters can be identified by the knowledge of the eigenvectors associated with the smallest non zero eigenvalues of , say (recall that ). Identifying is an essential task of a clustering algorithm, since if is close to the reliability of the method is reduced. The -th spectral gap is often considered as a stability indicator. This difference can be seen as an unstructured distance between and an arbitrary symmetric matrix with vanishing -th spectral gap. A more appropriate structured distance to ambiguity such that represents the Laplacian of a graph has been proposed in Andreotti et al. (2021) . This is defined as the minimal distance between and Laplacians of graphs with the same vertices and edges, but with weights that are perturbed such that the -th spectral gap vanishes. In this article we consider a slightly different approach, still based on the reformulation of the problem into the minimization of a suitable functional in the eigenvalues. After determining the gradient system associated with this functional, we introduce a low-rank projected system, suggested by the underlying low-rank structure of the extremizers of the problem. The integration of this low-rank system, requires both a moderate computational effort and a memory requirement, as it is shown in some illustrative numerical examples.
{"title":"A low-rank ODE for spectral clustering stability","authors":"Nicola Guglielmi, Stefano Sicilia","doi":"10.1016/j.laa.2024.07.001","DOIUrl":"https://doi.org/10.1016/j.laa.2024.07.001","url":null,"abstract":"Spectral clustering is a well-known technique which identifies clusters in an undirected graph, with vertices and weight matrix , by exploiting its graph Laplacian . In particular, the clusters can be identified by the knowledge of the eigenvectors associated with the smallest non zero eigenvalues of , say (recall that ). Identifying is an essential task of a clustering algorithm, since if is close to the reliability of the method is reduced. The -th spectral gap is often considered as a stability indicator. This difference can be seen as an unstructured distance between and an arbitrary symmetric matrix with vanishing -th spectral gap. A more appropriate structured distance to ambiguity such that represents the Laplacian of a graph has been proposed in Andreotti et al. (2021) . This is defined as the minimal distance between and Laplacians of graphs with the same vertices and edges, but with weights that are perturbed such that the -th spectral gap vanishes. In this article we consider a slightly different approach, still based on the reformulation of the problem into the minimization of a suitable functional in the eigenvalues. After determining the gradient system associated with this functional, we introduce a low-rank projected system, suggested by the underlying low-rank structure of the extremizers of the problem. The integration of this low-rank system, requires both a moderate computational effort and a memory requirement, as it is shown in some illustrative numerical examples.","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-06DOI: 10.1016/j.laa.2024.07.003
In the Analytic Hierarchy Process (AHP) the efficient vectors for a pairwise comparison matrix (PC matrix) are based on the principle of Pareto optimal decisions. To infer the efficiency of a vector for a PC matrix we construct a directed Hamiltonian cycle of a certain digraph associated with the PC matrix and the vector. We describe advantages of using this process over using the strong connectivity of the digraph. As an application of our process we find efficient vectors for a PC matrix, A, obtained from a consistent one by perturbing three entries above the main diagonal and the corresponding reciprocal entries, in a way that there is a square submatrix of A of order 2 containing three of the perturbed entries and not containing a diagonal entry of A. For completeness, we include examples showing conditions under which, when deleting a certain entry of an efficient vector for the square matrix A of order n, we have a non-efficient vector for the corresponding square principal submatrix of order n-1 of A.
在层次分析法(AHP)中,成对比较矩阵(PC 矩阵)的有效向量是基于帕累托最优决策原则。为了推断 PC 矩阵向量的效率,我们构建了与 PC 矩阵和向量相关联的某个数图的有向哈密顿循环。我们描述了使用这一过程比使用数图的强连接性更有优势。作为我们过程的一个应用,我们为 PC 矩阵 A 找到了有效的向量,该矩阵是通过扰动主对角线上方的三个条目和相应的倒数条目从一致矩阵中得到的,其方式是 A 的阶数为 2 的正方形子矩阵包含三个扰动条目,且不包含 A 的对角线条目。为完整起见,我们举例说明在删除 n 阶正方形矩阵 A 的有效向量的某个条目时,A 的 n-1 阶正方形主子矩阵相应的非有效向量的条件。
{"title":"Positive vectors, pairwise comparison matrices and directed Hamiltonian cycles","authors":"","doi":"10.1016/j.laa.2024.07.003","DOIUrl":"10.1016/j.laa.2024.07.003","url":null,"abstract":"<div><p>In the Analytic Hierarchy Process (AHP) the efficient vectors for a pairwise comparison matrix (PC matrix) are based on the principle of Pareto optimal decisions. To infer the efficiency of a vector for a PC matrix we construct a directed Hamiltonian cycle of a certain digraph associated with the PC matrix and the vector. We describe advantages of using this process over using the strong connectivity of the digraph. As an application of our process we find efficient vectors for a PC matrix, A, obtained from a consistent one by perturbing three entries above the main diagonal and the corresponding reciprocal entries, in a way that there is a square submatrix of A of order 2 containing three of the perturbed entries and not containing a diagonal entry of A. For completeness, we include examples showing conditions under which, when deleting a certain entry of an efficient vector for the square matrix A of order n, we have a non-efficient vector for the corresponding square principal submatrix of order n-1 of A.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0024379524002854/pdfft?md5=275e7043d1166d9276511bf66ea2c7ed&pid=1-s2.0-S0024379524002854-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-06DOI: 10.1016/j.laa.2024.07.002
A P-matrix is a matrix all of whose principal minors are positive. We demonstrate that the fractional powers of a P-matrix are also P-matrices. This insight allows us to affirmatively address a longstanding conjecture raised in Hershkowitz and Johnson (1986) [8]: It is shown that if is a P-matrix for all positive integers k, then the eigenvalues of A are positive.
{"title":"P-matrix powers","authors":"","doi":"10.1016/j.laa.2024.07.002","DOIUrl":"10.1016/j.laa.2024.07.002","url":null,"abstract":"<div><p>A <em>P</em>-matrix is a matrix all of whose principal minors are positive. We demonstrate that the fractional powers of a <em>P</em>-matrix are also <em>P</em>-matrices. This insight allows us to affirmatively address a longstanding conjecture raised in Hershkowitz and Johnson (1986) <span><span>[8]</span></span>: It is shown that if <span><math><msup><mrow><mi>A</mi></mrow><mrow><mi>k</mi></mrow></msup></math></span> is a <em>P</em>-matrix for all positive integers <em>k</em>, then the eigenvalues of <em>A</em> are positive.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}