Pub Date : 2024-09-03DOI: 10.1016/j.laa.2024.08.020
Cheng Yeaw Ku , Kok Bin Wong
Let G be a connected uniform hypergraph and be the adjacency tensor of G. The largest absolute value of the eigenvalues of is called the spectral radius of G. The number of eigenvectors of associated with the spectral radius is called the stabilizing index of G. The number of eigenvalues of with modulus equal to the spectral radius is called the cyclic index of G. In this paper, we consider a class of amalgamated uniform hypergraphs and compute its stabilizing index and cyclic index.
设 G 是一个连通的均匀超图,A(G) 是 G 的邻接张量。A(G) 的特征值的最大绝对值称为 G 的谱半径。模等于谱半径的 A(G) 特征值的个数称为 G 的循环指数。本文考虑一类汞齐均匀超图,并计算其稳定指数和循环指数。
{"title":"On stabilizing index and cyclic index of certain amalgamated uniform hypergraphs","authors":"Cheng Yeaw Ku , Kok Bin Wong","doi":"10.1016/j.laa.2024.08.020","DOIUrl":"10.1016/j.laa.2024.08.020","url":null,"abstract":"<div><p>Let <em>G</em> be a connected uniform hypergraph and <span><math><mi>A</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> be the adjacency tensor of <em>G</em>. The largest absolute value of the eigenvalues of <span><math><mi>A</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> is called the spectral radius of <em>G</em>. The number of eigenvectors of <span><math><mi>A</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> associated with the spectral radius is called the stabilizing index of <em>G</em>. The number of eigenvalues of <span><math><mi>A</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> with modulus equal to the spectral radius is called the cyclic index of <em>G</em>. In this paper, we consider a class of amalgamated uniform hypergraphs and compute its stabilizing index and cyclic index.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142169244","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 : 2024-09-03DOI: 10.1016/j.laa.2024.08.021
Sarula Chang , Jianxi Li , Yirong Zheng
Let , and be the multiplicity of an eigenvalue λ, the cyclomatic number and the number of pendant vertices of a connected graph G, respectively. Yang et al. (2023) [10] proved that for any tree T, and characterized all trees T with , where is the line graph of T. In this paper, we extend their result from a tree T to any graph , and prove that for any graph . Moreover, all graphs G with are completely characterized.
设 m(G,λ)、c(G) 和 p(G) 分别为连通图 G 的特征值 λ 的倍率、循环数和挂顶点数。Yang 等人(2023)[10] 证明了对于任意树 T,m(L(T),λ)≤p(T)-1,并表征了 m(L(T),λ)=p(T)-1 的所有树 T,其中 L(T) 是 T 的线图。本文将他们的结果从树 T 扩展到任何图 G≠Cn,并证明对于任何图 G≠Cn,m(L(G),λ)≤2c(G)+p(G)-1。此外,m(L(G),-1)=2c(G)+p(G)-1 的所有图形 G 都是完全表征的。
{"title":"The eigenvalue multiplicity of line graphs","authors":"Sarula Chang , Jianxi Li , Yirong Zheng","doi":"10.1016/j.laa.2024.08.021","DOIUrl":"10.1016/j.laa.2024.08.021","url":null,"abstract":"<div><p>Let <span><math><mi>m</mi><mo>(</mo><mi>G</mi><mo>,</mo><mi>λ</mi><mo>)</mo></math></span>, <span><math><mi>c</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> and <span><math><mi>p</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> be the multiplicity of an eigenvalue <em>λ</em>, the cyclomatic number and the number of pendant vertices of a connected graph <em>G</em>, respectively. Yang et al. (2023) <span><span>[10]</span></span> proved that <span><math><mi>m</mi><mo>(</mo><mi>L</mi><mo>(</mo><mi>T</mi><mo>)</mo><mo>,</mo><mi>λ</mi><mo>)</mo><mo>≤</mo><mi>p</mi><mo>(</mo><mi>T</mi><mo>)</mo><mo>−</mo><mn>1</mn></math></span> for any tree <em>T</em>, and characterized all trees <em>T</em> with <span><math><mi>m</mi><mo>(</mo><mi>L</mi><mo>(</mo><mi>T</mi><mo>)</mo><mo>,</mo><mi>λ</mi><mo>)</mo><mo>=</mo><mi>p</mi><mo>(</mo><mi>T</mi><mo>)</mo><mo>−</mo><mn>1</mn></math></span>, where <span><math><mi>L</mi><mo>(</mo><mi>T</mi><mo>)</mo></math></span> is the line graph of <em>T</em>. In this paper, we extend their result from a tree <em>T</em> to any graph <span><math><mi>G</mi><mo>≠</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>, and prove that <span><math><mi>m</mi><mo>(</mo><mi>L</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>,</mo><mi>λ</mi><mo>)</mo><mo>≤</mo><mn>2</mn><mi>c</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>+</mo><mi>p</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>−</mo><mn>1</mn></math></span> for any graph <span><math><mi>G</mi><mo>≠</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>. Moreover, all graphs <em>G</em> with <span><math><mi>m</mi><mo>(</mo><mi>L</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>,</mo><mo>−</mo><mn>1</mn><mo>)</mo><mo>=</mo><mn>2</mn><mi>c</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>+</mo><mi>p</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>−</mo><mn>1</mn></math></span> are completely characterized.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142163933","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 : 2024-08-30DOI: 10.1016/j.laa.2024.08.019
Shaowu Huang , Hemant K. Mishra
Symplectic eigenvalues are known to satisfy analogs of several classic eigenvalue inequalities. Of these is a set of weak supermajorization relations concerning symplectic eigenvalues that are weaker analogs of some majorization relations corresponding to eigenvalues. The aim of this letter is to establish necessary and sufficient conditions for the saturation of the symplectic weak supermajorization relations by majorization.
{"title":"Majorization in some symplectic weak supermajorizations","authors":"Shaowu Huang , Hemant K. Mishra","doi":"10.1016/j.laa.2024.08.019","DOIUrl":"10.1016/j.laa.2024.08.019","url":null,"abstract":"<div><p>Symplectic eigenvalues are known to satisfy analogs of several classic eigenvalue inequalities. Of these is a set of weak supermajorization relations concerning symplectic eigenvalues that are weaker analogs of some majorization relations corresponding to eigenvalues. The aim of this letter is to establish necessary and sufficient conditions for the saturation of the symplectic weak supermajorization relations by majorization.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142129945","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 : 2024-08-30DOI: 10.1016/j.laa.2024.08.017
Alexandru Chirvasitu
For any square-summable commuting family of complex matrices there is a normal commuting family no farther from it, in squared normalized distance, than the diameter of the numerical range of . Specializing in one direction (limiting case of the inequality for finite I) this recovers a result of M. Fraas: if is a multiple of the identity for commuting then the are normal; specializing in another (singleton I) retrieves the well-known fact that close-to-isometric matrices are close to isometries.
{"title":"Normal approximations of commuting square-summable matrix families","authors":"Alexandru Chirvasitu","doi":"10.1016/j.laa.2024.08.017","DOIUrl":"10.1016/j.laa.2024.08.017","url":null,"abstract":"<div><p>For any square-summable commuting family <span><math><msub><mrow><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>)</mo></mrow><mrow><mi>i</mi><mo>∈</mo><mi>I</mi></mrow></msub></math></span> of complex <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> matrices there is a normal commuting family <span><math><msub><mrow><mo>(</mo><msub><mrow><mi>B</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>)</mo></mrow><mrow><mi>i</mi></mrow></msub></math></span> no farther from it, in squared normalized <span><math><msup><mrow><mi>ℓ</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> distance, than the diameter of the numerical range of <span><math><msub><mrow><mo>∑</mo></mrow><mrow><mi>i</mi></mrow></msub><msubsup><mrow><mi>A</mi></mrow><mrow><mi>i</mi></mrow><mrow><mo>⁎</mo></mrow></msubsup><msub><mrow><mi>A</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span>. Specializing in one direction (limiting case of the inequality for finite <em>I</em>) this recovers a result of M. Fraas: if <span><math><msubsup><mrow><mo>∑</mo></mrow><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>ℓ</mi></mrow></msubsup><msubsup><mrow><mi>A</mi></mrow><mrow><mi>i</mi></mrow><mrow><mo>⁎</mo></mrow></msubsup><msub><mrow><mi>A</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span> is a multiple of the identity for commuting <span><math><msub><mrow><mi>A</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><mi>C</mi><mo>)</mo></math></span> then the <span><math><msub><mrow><mi>A</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span> are normal; specializing in another (singleton <em>I</em>) retrieves the well-known fact that close-to-isometric matrices are close to isometries.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142129943","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 : 2024-08-29DOI: 10.1016/j.laa.2024.08.018
Thomas Ransford , Dashdondog Tsedenbayar
Let T be an injective bounded linear operator on a complex Hilbert space. We characterize the complex numbers for which is a contraction, the characterization being expressed in terms of the numerical range of the possibly unbounded operator .
When , the Volterra operator on , this leads to a result of Khadkhuu, Zemánek and the second author, characterizing those for which is a contraction. Taking , we further deduce that is never a contraction if and .
{"title":"Contractivity of Möbius functions of operators","authors":"Thomas Ransford , Dashdondog Tsedenbayar","doi":"10.1016/j.laa.2024.08.018","DOIUrl":"10.1016/j.laa.2024.08.018","url":null,"abstract":"<div><p>Let <em>T</em> be an injective bounded linear operator on a complex Hilbert space. We characterize the complex numbers <span><math><mi>λ</mi><mo>,</mo><mi>μ</mi></math></span> for which <span><math><mo>(</mo><mi>I</mi><mo>+</mo><mi>λ</mi><mi>T</mi><mo>)</mo><msup><mrow><mo>(</mo><mi>I</mi><mo>+</mo><mi>μ</mi><mi>T</mi><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> is a contraction, the characterization being expressed in terms of the numerical range of the possibly unbounded operator <span><math><msup><mrow><mi>T</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>.</p><p>When <span><math><mi>T</mi><mo>=</mo><mi>V</mi></math></span>, the Volterra operator on <span><math><msup><mrow><mi>L</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>[</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>]</mo></math></span>, this leads to a result of Khadkhuu, Zemánek and the second author, characterizing those <span><math><mi>λ</mi><mo>,</mo><mi>μ</mi></math></span> for which <span><math><mo>(</mo><mi>I</mi><mo>+</mo><mi>λ</mi><mi>V</mi><mo>)</mo><msup><mrow><mo>(</mo><mi>I</mi><mo>+</mo><mi>μ</mi><mi>V</mi><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> is a contraction. Taking <span><math><mi>T</mi><mo>=</mo><msup><mrow><mi>V</mi></mrow><mrow><mi>n</mi></mrow></msup></math></span>, we further deduce that <span><math><mo>(</mo><mi>I</mi><mo>+</mo><mi>λ</mi><msup><mrow><mi>V</mi></mrow><mrow><mi>n</mi></mrow></msup><mo>)</mo><msup><mrow><mo>(</mo><mi>I</mi><mo>+</mo><mi>μ</mi><msup><mrow><mi>V</mi></mrow><mrow><mi>n</mi></mrow></msup><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> is never a contraction if <span><math><mi>n</mi><mo>≥</mo><mn>2</mn></math></span> and <span><math><mi>λ</mi><mo>≠</mo><mi>μ</mi></math></span>.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142136750","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 : 2024-08-28DOI: 10.1016/j.laa.2024.08.016
Gi-Sang Cheon , Bumtle Kang , Suh-Ryung Kim , Homoon Ryu
<div><p>This paper is a follow-up to the paper of Cheon et al. (2023) <span><span>[2]</span></span>. Given subsets <em>S</em> and <em>T</em> of <span><math><mo>{</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>n</mi><mo>−</mo><mn>1</mn><mo>}</mo></math></span>, an <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> Toeplitz matrix <span><math><mi>A</mi><mo>=</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>〈</mo><mi>S</mi><mo>;</mo><mi>T</mi><mo>〉</mo></math></span> is defined to have 1 as the <span><math><mo>(</mo><mi>i</mi><mo>,</mo><mi>j</mi><mo>)</mo></math></span>-entry if and only if <span><math><mi>j</mi><mo>−</mo><mi>i</mi><mo>∈</mo><mi>S</mi></math></span> or <span><math><mi>i</mi><mo>−</mo><mi>j</mi><mo>∈</mo><mi>T</mi></math></span>. In the previous paper, we have shown that the matrix period and the competition period of Toeplitz matrices <span><math><mi>A</mi><mo>=</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>〈</mo><mi>S</mi><mo>;</mo><mi>T</mi><mo>〉</mo></math></span> satisfying the condition (⋆) <span><math><mi>max</mi><mo></mo><mi>S</mi><mo>+</mo><mi>min</mi><mo></mo><mi>T</mi><mo>≤</mo><mi>n</mi></math></span> and <span><math><mi>min</mi><mo></mo><mi>S</mi><mo>+</mo><mi>max</mi><mo></mo><mi>T</mi><mo>≤</mo><mi>n</mi></math></span> are <span><math><msup><mrow><mi>d</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>/</mo><mi>d</mi></math></span> and 1, respectively, where <span><math><msup><mrow><mi>d</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>=</mo><mi>gcd</mi><mo></mo><mo>(</mo><mi>s</mi><mo>+</mo><mi>t</mi><mo>|</mo><mi>s</mi><mo>∈</mo><mi>S</mi><mo>,</mo><mi>t</mi><mo>∈</mo><mi>T</mi><mo>)</mo></math></span> and <span><math><mi>d</mi><mo>=</mo><mi>gcd</mi><mo></mo><mo>(</mo><mi>d</mi><mo>,</mo><mi>min</mi><mo></mo><mi>S</mi><mo>)</mo></math></span>. In this paper, we claim that even if (⋆) is relaxed to the existence of elements <span><math><mi>s</mi><mo>∈</mo><mi>S</mi></math></span> and <span><math><mi>t</mi><mo>∈</mo><mi>T</mi></math></span> satisfying <span><math><mi>s</mi><mo>+</mo><mi>t</mi><mo>≤</mo><mi>n</mi></math></span> and <span><math><mi>gcd</mi><mo></mo><mo>(</mo><mi>s</mi><mo>,</mo><mi>t</mi><mo>)</mo><mo>=</mo><mn>1</mn></math></span>, the same result holds. There are infinitely many Toeplitz matrices that do not satisfy (⋆) but the relaxed condition. For example, for any positive integers <span><math><mi>k</mi><mo>,</mo><mi>n</mi></math></span> with <span><math><mn>2</mn><mi>k</mi><mo>+</mo><mn>1</mn><mo>≤</mo><mi>n</mi></math></span>, it is easy to see that <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>〈</mo><mi>k</mi><mo>,</mo><mi>n</mi><mo>−</mo><mi>k</mi><mo>;</mo><mi>k</mi><mo>+</mo><mn>1</mn><mo>,</mo><mi>n</mi><mo>−</mo><mi>k</mi><mo>−</mo><mn>1</mn><mo>〉</mo></math></span> does not satisfy (⋆) but satisfies the relaxed condition. Furthermore, we show that the limit of the matrix sequence <span><math><msubsup><mrow><mo>{</mo><
{"title":"Matrix periods and competition periods of Boolean Toeplitz matrices II","authors":"Gi-Sang Cheon , Bumtle Kang , Suh-Ryung Kim , Homoon Ryu","doi":"10.1016/j.laa.2024.08.016","DOIUrl":"10.1016/j.laa.2024.08.016","url":null,"abstract":"<div><p>This paper is a follow-up to the paper of Cheon et al. (2023) <span><span>[2]</span></span>. Given subsets <em>S</em> and <em>T</em> of <span><math><mo>{</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>n</mi><mo>−</mo><mn>1</mn><mo>}</mo></math></span>, an <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> Toeplitz matrix <span><math><mi>A</mi><mo>=</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>〈</mo><mi>S</mi><mo>;</mo><mi>T</mi><mo>〉</mo></math></span> is defined to have 1 as the <span><math><mo>(</mo><mi>i</mi><mo>,</mo><mi>j</mi><mo>)</mo></math></span>-entry if and only if <span><math><mi>j</mi><mo>−</mo><mi>i</mi><mo>∈</mo><mi>S</mi></math></span> or <span><math><mi>i</mi><mo>−</mo><mi>j</mi><mo>∈</mo><mi>T</mi></math></span>. In the previous paper, we have shown that the matrix period and the competition period of Toeplitz matrices <span><math><mi>A</mi><mo>=</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>〈</mo><mi>S</mi><mo>;</mo><mi>T</mi><mo>〉</mo></math></span> satisfying the condition (⋆) <span><math><mi>max</mi><mo></mo><mi>S</mi><mo>+</mo><mi>min</mi><mo></mo><mi>T</mi><mo>≤</mo><mi>n</mi></math></span> and <span><math><mi>min</mi><mo></mo><mi>S</mi><mo>+</mo><mi>max</mi><mo></mo><mi>T</mi><mo>≤</mo><mi>n</mi></math></span> are <span><math><msup><mrow><mi>d</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>/</mo><mi>d</mi></math></span> and 1, respectively, where <span><math><msup><mrow><mi>d</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>=</mo><mi>gcd</mi><mo></mo><mo>(</mo><mi>s</mi><mo>+</mo><mi>t</mi><mo>|</mo><mi>s</mi><mo>∈</mo><mi>S</mi><mo>,</mo><mi>t</mi><mo>∈</mo><mi>T</mi><mo>)</mo></math></span> and <span><math><mi>d</mi><mo>=</mo><mi>gcd</mi><mo></mo><mo>(</mo><mi>d</mi><mo>,</mo><mi>min</mi><mo></mo><mi>S</mi><mo>)</mo></math></span>. In this paper, we claim that even if (⋆) is relaxed to the existence of elements <span><math><mi>s</mi><mo>∈</mo><mi>S</mi></math></span> and <span><math><mi>t</mi><mo>∈</mo><mi>T</mi></math></span> satisfying <span><math><mi>s</mi><mo>+</mo><mi>t</mi><mo>≤</mo><mi>n</mi></math></span> and <span><math><mi>gcd</mi><mo></mo><mo>(</mo><mi>s</mi><mo>,</mo><mi>t</mi><mo>)</mo><mo>=</mo><mn>1</mn></math></span>, the same result holds. There are infinitely many Toeplitz matrices that do not satisfy (⋆) but the relaxed condition. For example, for any positive integers <span><math><mi>k</mi><mo>,</mo><mi>n</mi></math></span> with <span><math><mn>2</mn><mi>k</mi><mo>+</mo><mn>1</mn><mo>≤</mo><mi>n</mi></math></span>, it is easy to see that <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>〈</mo><mi>k</mi><mo>,</mo><mi>n</mi><mo>−</mo><mi>k</mi><mo>;</mo><mi>k</mi><mo>+</mo><mn>1</mn><mo>,</mo><mi>n</mi><mo>−</mo><mi>k</mi><mo>−</mo><mn>1</mn><mo>〉</mo></math></span> does not satisfy (⋆) but satisfies the relaxed condition. Furthermore, we show that the limit of the matrix sequence <span><math><msubsup><mrow><mo>{</mo><","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142148823","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 : 2024-08-23DOI: 10.1016/j.laa.2024.08.015
Gao-Xuan Luo, Shi-Cai Gong , Jing Tian
Let G be a connected simple graph with order n and Laplacian matrix . The Laplacian-energy-like of G is defined as where is the eigenvalue of for . In this paper, with the aid of Ferrers diagrams of threshold graphs, we provide an algebraic combinatorial approach to determine the graphs with minimal Laplacian-energy-like among all connected graphs having n vertices and m edges, showing that the extremal graph is a special threshold graph, named as the quasi-complete graph.
设 G 是阶数为 n 的连通简单图,且有拉普拉斯矩阵 L(G)。G 的类拉普拉奇能量定义为:LEL(G)=∑i=1nλi,其中,λi 是 L(G) i=1,...,n 时的特征值。本文借助阈值图的费勒斯图,提供了一种代数组合方法,以确定在具有 n 个顶点和 m 条边的所有连通图中具有最小拉普拉奇能样的图,证明极值图是一种特殊的阈值图,命名为准完全图。
{"title":"Minimizing the Laplacian-energy-like of graphs","authors":"Gao-Xuan Luo, Shi-Cai Gong , Jing Tian","doi":"10.1016/j.laa.2024.08.015","DOIUrl":"10.1016/j.laa.2024.08.015","url":null,"abstract":"<div><p>Let <em>G</em> be a connected simple graph with order <em>n</em> and Laplacian matrix <span><math><mi>L</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span>. The Laplacian-energy-like of <em>G</em> is defined as<span><span><span><math><mi>L</mi><mi>E</mi><mi>L</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>=</mo><munderover><mo>∑</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>n</mi></mrow></munderover><msqrt><mrow><msub><mrow><mi>λ</mi></mrow><mrow><mi>i</mi></mrow></msub></mrow></msqrt><mo>,</mo></math></span></span></span> where <span><math><msub><mrow><mi>λ</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span> is the eigenvalue of <span><math><mi>L</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> for <span><math><mi>i</mi><mo>=</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>n</mi></math></span>. In this paper, with the aid of Ferrers diagrams of threshold graphs, we provide an algebraic combinatorial approach to determine the graphs with minimal Laplacian-energy-like among all connected graphs having <em>n</em> vertices and <em>m</em> edges, showing that the extremal graph is a special threshold graph, named as the quasi-complete graph.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142097782","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 : 2024-08-22DOI: 10.1016/j.laa.2024.08.014
Mark Pencovitch
Expanding on work by Conway, Orson, and Powell, we study the isotopy classes rel. boundary of nonorientable, compact, locally flatly embedded surfaces in with knot group .
In particular we show that if two such surfaces have the same normal Euler number, the same fixed knot boundary K such that , and the same nonorientable genus 4 or 5, then they are ambiently isotopic rel. boundary.
This implies that closed, nonorientable, locally flatly embedded surfaces in the 4-sphere with knot group of nonorientable genus 4 and 5 are topologically unknotted. The proof relies on calculations, implemented in Sage, which imply that an obstruction to modified surgery is elementary. Furthermore we show that this method fails for nonorientable genus 6 and 7.
{"title":"Unknotting nonorientable surfaces of genus 4 and 5","authors":"Mark Pencovitch","doi":"10.1016/j.laa.2024.08.014","DOIUrl":"10.1016/j.laa.2024.08.014","url":null,"abstract":"<div><p>Expanding on work by Conway, Orson, and Powell, we study the isotopy classes rel. boundary of nonorientable, compact, locally flatly embedded surfaces in <span><math><msup><mrow><mi>D</mi></mrow><mrow><mn>4</mn></mrow></msup></math></span> with knot group <span><math><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>.</p><p>In particular we show that if two such surfaces have the same normal Euler number, the same fixed knot boundary <em>K</em> such that <span><math><mo>|</mo><mi>det</mi><mo></mo><mo>(</mo><mi>K</mi><mo>)</mo><mo>|</mo><mo>=</mo><mn>1</mn></math></span>, and the same nonorientable genus 4 or 5, then they are ambiently isotopic rel. boundary.</p><p>This implies that closed, nonorientable, locally flatly embedded surfaces in the 4-sphere with knot group <span><math><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> of nonorientable genus 4 and 5 are topologically unknotted. The proof relies on calculations, implemented in Sage, which imply that an obstruction to modified surgery is elementary. Furthermore we show that this method fails for nonorientable genus 6 and 7.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0024379524003410/pdfft?md5=b5b1d92c3f68749bd2133863f112514f&pid=1-s2.0-S0024379524003410-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142097783","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 : 2024-08-22DOI: 10.1016/j.laa.2024.07.024
Fernando De Terán , Andrii Dmytryshyn , Froilán M. Dopico
We show that the set of complex skew-symmetric matrix polynomials of even grade d, i.e., of degree at most d, and (normal) rank at most 2r is the closure of the single set of matrix polynomials with certain, explicitly described, complete eigenstructure. This complete eigenstructure corresponds to the most generic complex skew-symmetric matrix polynomials of even grade d and rank at most 2r. The analogous problem for the case of skew-symmetric matrix polynomials of odd grade is solved in [24].
我们证明,偶数级 d 的 m×m 复数偏斜对称矩阵多项式集合,即最多 d 级和(正常)最多 2r 级,是具有某些明确描述的完整特征结构的单个矩阵多项式集合的闭集。这个完整的特征结构对应于偶数级 d、秩至多 2r 的最一般的 m×m 复数偏斜对称矩阵多项式。奇数级的倾斜对称矩阵多项式的类似问题已在 [24] 中解决。
{"title":"Even grade generic skew-symmetric matrix polynomials with bounded rank","authors":"Fernando De Terán , Andrii Dmytryshyn , Froilán M. Dopico","doi":"10.1016/j.laa.2024.07.024","DOIUrl":"10.1016/j.laa.2024.07.024","url":null,"abstract":"<div><p>We show that the set of <span><math><mi>m</mi><mo>×</mo><mi>m</mi></math></span> complex skew-symmetric matrix polynomials of even grade <em>d</em>, i.e., of degree at most <em>d</em>, and (normal) rank at most 2<em>r</em> is the closure of the single set of matrix polynomials with certain, explicitly described, complete eigenstructure. This complete eigenstructure corresponds to the most generic <span><math><mi>m</mi><mo>×</mo><mi>m</mi></math></span> complex skew-symmetric matrix polynomials of even grade <em>d</em> and rank at most 2<em>r</em>. The analogous problem for the case of skew-symmetric matrix polynomials of odd grade is solved in <span><span>[24]</span></span>.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0024379524003148/pdfft?md5=b302119931c35a517772b4d30a8c6bde&pid=1-s2.0-S0024379524003148-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142097784","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}
<div><p>Let <span><math><mn>1</mn><mo><</mo><mi>t</mi><mo><</mo><mi>n</mi></math></span> be integers, where <em>t</em> is a divisor of <em>n</em>. An <span><math><mi>R-</mi><mspace></mspace><msup><mrow><mi>q</mi></mrow><mrow><mi>t</mi></mrow></msup></math></span>-partially scattered polynomial is a <em>q</em>-polynomial <em>f</em> in <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub><mo>[</mo><mi>X</mi><mo>]</mo></math></span> that satisfies the condition that for all <span><math><mi>x</mi><mo>,</mo><mi>y</mi><mo>∈</mo><msubsup><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow><mrow><mo>⁎</mo></mrow></msubsup></math></span> such that <span><math><mi>x</mi><mo>/</mo><mi>y</mi><mo>∈</mo><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>t</mi></mrow></msup></mrow></msub></math></span>, if <span><math><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo>/</mo><mi>x</mi><mo>=</mo><mi>f</mi><mo>(</mo><mi>y</mi><mo>)</mo><mo>/</mo><mi>y</mi></math></span>, then <span><math><mi>x</mi><mo>/</mo><mi>y</mi><mo>∈</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub></math></span>; <em>f</em> is called scattered if this implication holds for all <span><math><mi>x</mi><mo>,</mo><mi>y</mi><mo>∈</mo><msubsup><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow><mrow><mo>⁎</mo></mrow></msubsup></math></span>. Two polynomials in <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub><mo>[</mo><mi>X</mi><mo>]</mo></math></span> are said to be equivalent if their graphs are in the same orbit under the action of the group <span><math><mrow><mi>Γ</mi><mi>L</mi></mrow><mo>(</mo><mn>2</mn><mo>,</mo><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup><mo>)</mo></math></span>. For <span><math><mi>n</mi><mo>></mo><mn>8</mn></math></span> only three families of scattered polynomials in <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub><mo>[</mo><mi>X</mi><mo>]</mo></math></span> are known: (<em>i</em>) monomials of pseudoregulus type, <span><math><mo>(</mo><mi>i</mi><mi>i</mi><mo>)</mo></math></span> binomials of Lunardon-Polverino type, and <span><math><mo>(</mo><mi>i</mi><mi>i</mi><mi>i</mi><mo>)</mo></math></span> a family of quadrinomials defined in <span><span>[1]</span></span>, <span><span>[10]</span></span> and extended in <span><span>[8]</span></span>, <span><span>[13]</span></span>. In this paper we prove that the polynomial <span><math><msub><mrow><mi>φ</mi></mrow><mrow><mi>m</mi><mo>,</mo><msup><mrow><mi>q</mi></mrow><mrow><mi>J</mi></mrow></msup></mrow></msub><mo>=</mo><msup><mrow><mi>X</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>J</mi><mo>(</mo><mi>t</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></msup></mrow></msup><mo>+</mo><
{"title":"New scattered linearized quadrinomials","authors":"Valentino Smaldore , Corrado Zanella , Ferdinando Zullo","doi":"10.1016/j.laa.2024.08.012","DOIUrl":"10.1016/j.laa.2024.08.012","url":null,"abstract":"<div><p>Let <span><math><mn>1</mn><mo><</mo><mi>t</mi><mo><</mo><mi>n</mi></math></span> be integers, where <em>t</em> is a divisor of <em>n</em>. An <span><math><mi>R-</mi><mspace></mspace><msup><mrow><mi>q</mi></mrow><mrow><mi>t</mi></mrow></msup></math></span>-partially scattered polynomial is a <em>q</em>-polynomial <em>f</em> in <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub><mo>[</mo><mi>X</mi><mo>]</mo></math></span> that satisfies the condition that for all <span><math><mi>x</mi><mo>,</mo><mi>y</mi><mo>∈</mo><msubsup><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow><mrow><mo>⁎</mo></mrow></msubsup></math></span> such that <span><math><mi>x</mi><mo>/</mo><mi>y</mi><mo>∈</mo><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>t</mi></mrow></msup></mrow></msub></math></span>, if <span><math><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo>/</mo><mi>x</mi><mo>=</mo><mi>f</mi><mo>(</mo><mi>y</mi><mo>)</mo><mo>/</mo><mi>y</mi></math></span>, then <span><math><mi>x</mi><mo>/</mo><mi>y</mi><mo>∈</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub></math></span>; <em>f</em> is called scattered if this implication holds for all <span><math><mi>x</mi><mo>,</mo><mi>y</mi><mo>∈</mo><msubsup><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow><mrow><mo>⁎</mo></mrow></msubsup></math></span>. Two polynomials in <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub><mo>[</mo><mi>X</mi><mo>]</mo></math></span> are said to be equivalent if their graphs are in the same orbit under the action of the group <span><math><mrow><mi>Γ</mi><mi>L</mi></mrow><mo>(</mo><mn>2</mn><mo>,</mo><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup><mo>)</mo></math></span>. For <span><math><mi>n</mi><mo>></mo><mn>8</mn></math></span> only three families of scattered polynomials in <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub><mo>[</mo><mi>X</mi><mo>]</mo></math></span> are known: (<em>i</em>) monomials of pseudoregulus type, <span><math><mo>(</mo><mi>i</mi><mi>i</mi><mo>)</mo></math></span> binomials of Lunardon-Polverino type, and <span><math><mo>(</mo><mi>i</mi><mi>i</mi><mi>i</mi><mo>)</mo></math></span> a family of quadrinomials defined in <span><span>[1]</span></span>, <span><span>[10]</span></span> and extended in <span><span>[8]</span></span>, <span><span>[13]</span></span>. In this paper we prove that the polynomial <span><math><msub><mrow><mi>φ</mi></mrow><mrow><mi>m</mi><mo>,</mo><msup><mrow><mi>q</mi></mrow><mrow><mi>J</mi></mrow></msup></mrow></msub><mo>=</mo><msup><mrow><mi>X</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>J</mi><mo>(</mo><mi>t</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></msup></mrow></msup><mo>+</mo><","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0024379524003331/pdfft?md5=0868d48ffbb0ce34705f89a2a1932662&pid=1-s2.0-S0024379524003331-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142075901","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}