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":"703 ","pages":"Pages 11-19"},"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":"703 ","pages":"Pages 20-26"},"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":"703 ","pages":"Pages 27-46"},"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":"702 ","pages":"Pages 179-194"},"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":"702 ","pages":"Pages 195-217"},"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":"702 ","pages":"Pages 218-239"},"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":"702 ","pages":"Pages 143-160"},"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}
Pub Date : 2024-08-21DOI: 10.1016/j.laa.2024.08.011
M.I. Bueno , Susana Furtado
It is well-established that, for an singular k-banded complex matrix B, the submatrices of the Moore-Penrose inverse of B located strictly below (resp. above) its kth superdiagonal (resp. kth subdiagonal) have a certain bounded rank s depending on n, k and rankB. In this case, is said to satisfy a semiseparability condition. In this paper our focus is on singular strictly k-banded complex matrices B, and we show that the Moore-Penrose inverse of such a matrix satisfies a stronger condition, called generator representability. This means that there exist two matrices of rank at most s whose parts strictly below the kth diagonal (resp. above the kth subdiagonal) coincide with the same parts of . When , we prove that s is precisely the minimum rank of these two matrices. We also illustrate through examples that when those matrices may have rank less than s.
对于 n×n 奇异 k 带复矩阵 B,B 的摩尔-彭罗斯逆 B† 的子矩阵严格位于其第 k 个超对角线(或第 k 个次对角线)的下方(或上方),具有一定的有界秩 s,该秩取决于 n、k 和 rankB。在这种情况下,B† 满足半可分性条件。本文的重点是奇异的严格 k 带复矩阵 B,我们将证明这种矩阵的摩尔-彭罗斯逆满足一个更强的条件,即生成器可表示性。这意味着存在两个秩最多为 s 的矩阵,它们的第 k 条对角线以下(或第 k 条对角线以上)部分与 B† 的相同部分重合。当 n≥3k 时,我们证明 s 正是这两个矩阵的最小秩。我们还通过实例说明,当 n<3k 时,这些矩阵的秩可能小于 s。
{"title":"On the rank structure of the Moore-Penrose inverse of singular k-banded matrices","authors":"M.I. Bueno , Susana Furtado","doi":"10.1016/j.laa.2024.08.011","DOIUrl":"10.1016/j.laa.2024.08.011","url":null,"abstract":"<div><p>It is well-established that, for an <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> singular <em>k</em>-banded complex matrix <em>B</em>, the submatrices of the Moore-Penrose inverse <span><math><msup><mrow><mi>B</mi></mrow><mrow><mo>†</mo></mrow></msup></math></span> of <em>B</em> located strictly below (resp. above) its <em>k</em>th superdiagonal (resp. <em>k</em>th subdiagonal) have a certain bounded rank <em>s</em> depending on <em>n</em>, <em>k</em> and rank<em>B</em>. In this case, <span><math><msup><mrow><mi>B</mi></mrow><mrow><mo>†</mo></mrow></msup></math></span> is said to satisfy a semiseparability condition. In this paper our focus is on singular strictly <em>k</em>-banded complex matrices <em>B</em>, and we show that the Moore-Penrose inverse of such a matrix satisfies a stronger condition, called generator representability. This means that there exist two matrices of rank at most <em>s</em> whose parts strictly below the <em>k</em>th diagonal (resp. above the <em>k</em>th subdiagonal) coincide with the same parts of <span><math><msup><mrow><mi>B</mi></mrow><mrow><mo>†</mo></mrow></msup></math></span>. When <span><math><mi>n</mi><mo>≥</mo><mn>3</mn><mi>k</mi></math></span>, we prove that <em>s</em> is precisely the minimum rank of these two matrices. We also illustrate through examples that when <span><math><mi>n</mi><mo><</mo><mn>3</mn><mi>k</mi></math></span> those matrices may have rank less than <em>s</em>.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"702 ","pages":"Pages 122-142"},"PeriodicalIF":1.0,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142076637","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 : 2024-08-20DOI: 10.1016/j.laa.2024.08.013
Lucas J. Rusnak , Josephine Reynes , Russell Li , Eric Yan , Justin Yu
The determinants of -matrices are calculated via the oriented hypergraphic Laplacian and summing over incidence generalizations of vertex cycle-covers. These cycle-covers are signed and partitioned into families based on their hyperedge containment. Every non-edge-monic family is shown to contribute a net value of 0 to the Laplacian, while each edge-monic family is shown to sum to the absolute value of the determinant of the original incidence matrix. Simple symmetries are identified as well as their relationship to Hadamard's maximum determinant problem. Finally, the entries of the incidence matrix are reclaimed using only the signs of an adjacency-minimal set of cycle-covers from an edge-monic family.
{"title":"The determinant of {±1}-matrices and oriented hypergraphs","authors":"Lucas J. Rusnak , Josephine Reynes , Russell Li , Eric Yan , Justin Yu","doi":"10.1016/j.laa.2024.08.013","DOIUrl":"10.1016/j.laa.2024.08.013","url":null,"abstract":"<div><p>The determinants of <span><math><mo>{</mo><mo>±</mo><mn>1</mn><mo>}</mo></math></span>-matrices are calculated via the oriented hypergraphic Laplacian and summing over incidence generalizations of vertex cycle-covers. These cycle-covers are signed and partitioned into families based on their hyperedge containment. Every non-edge-monic family is shown to contribute a net value of 0 to the Laplacian, while each edge-monic family is shown to sum to the absolute value of the determinant of the original incidence matrix. Simple symmetries are identified as well as their relationship to Hadamard's maximum determinant problem. Finally, the entries of the incidence matrix are reclaimed using only the signs of an adjacency-minimal set of cycle-covers from an edge-monic family.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"702 ","pages":"Pages 161-178"},"PeriodicalIF":1.0,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142122630","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 : 2024-08-14DOI: 10.1016/j.laa.2024.08.008
Joseph Drapeau , Joseph Henderson , Peter Seely , Dallas Smith , Benjamin Webb
A classical result in spectral graph theory states that if a graph G has an equitable partition π then the eigenvalues of the divisor graph are a subset of its eigenvalues, i.e. . A natural question is whether it is possible to recover the remaining eigenvalues in a similar manner. Here we show that any weighted undirected graph with nontrivial equitable partition can be decomposed into a number of subgraphs whose collective spectra contain these remaining eigenvalues. Using this decomposition, which we refer to as a complete equitable decomposition, we introduce an algorithm for finding the eigenvalues of an undirected graph (symmetric matrix) with a nontrivial equitable partition. Under mild assumptions on this equitable partition we show that we can find eigenvalues of such a graph faster using this method when compared to standard methods. This is potentially useful as many real-world data sets are quite large and have a nontrivial equitable partition.
谱图理论中的一个经典结果表明,如果一个图 G 有一个公平分割 π,那么除法图 Gπ 的特征值就是其特征值的一个子集,即 σ(Gπ)⊆σ(G)。一个自然的问题是,是否有可能以类似的方式恢复其余的特征值 σ(G)-σ(Gπ)。在这里,我们将证明,任何具有非三等分的加权无向图都可以分解成若干子图,这些子图的集合谱包含这些剩余特征值。利用这种分解(我们称之为完全公平分解),我们引入了一种算法,用于找到具有非难公平分区的无向图(对称矩阵)的特征值。在对这种公平分区的温和假设下,我们证明,与标准方法相比,使用这种方法可以更快地找到这种图的特征值。这一点非常有用,因为现实世界中的许多数据集都相当大,而且具有非难等分区。
{"title":"Complete equitable decompositions","authors":"Joseph Drapeau , Joseph Henderson , Peter Seely , Dallas Smith , Benjamin Webb","doi":"10.1016/j.laa.2024.08.008","DOIUrl":"10.1016/j.laa.2024.08.008","url":null,"abstract":"<div><p>A classical result in spectral graph theory states that if a graph <em>G</em> has an equitable partition <em>π</em> then the eigenvalues of the divisor graph <span><math><msub><mrow><mi>G</mi></mrow><mrow><mi>π</mi></mrow></msub></math></span> are a subset of its eigenvalues, i.e. <span><math><mi>σ</mi><mo>(</mo><msub><mrow><mi>G</mi></mrow><mrow><mi>π</mi></mrow></msub><mo>)</mo><mo>⊆</mo><mi>σ</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span>. A natural question is whether it is possible to recover the remaining eigenvalues <span><math><mi>σ</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>−</mo><mi>σ</mi><mo>(</mo><msub><mrow><mi>G</mi></mrow><mrow><mi>π</mi></mrow></msub><mo>)</mo></math></span> in a similar manner. Here we show that any weighted undirected graph with nontrivial equitable partition can be decomposed into a number of subgraphs whose collective spectra contain these remaining eigenvalues. Using this decomposition, which we refer to as a complete equitable decomposition, we introduce an algorithm for finding the eigenvalues of an undirected graph (symmetric matrix) with a nontrivial equitable partition. Under mild assumptions on this equitable partition we show that we can find eigenvalues of such a graph faster using this method when compared to standard methods. This is potentially useful as many real-world data sets are quite large and have a nontrivial equitable partition.</p></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"701 ","pages":"Pages 112-137"},"PeriodicalIF":1.0,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142050069","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}