Lucio Centrone , Alexei Kanel-Belov , Roberto La Scala
{"title":"On the regularity of the language of some T-ideals","authors":"Lucio Centrone , Alexei Kanel-Belov , Roberto La Scala","doi":"10.1016/j.laa.2025.08.002","DOIUrl":"10.1016/j.laa.2025.08.002","url":null,"abstract":"<div><div>We consider an algebra satisfying a polynomial identity (PI-algebra) and we define what the language generated by its <em>T</em>-ideal is. We conjecture the <em>T</em>-ideal of any PI-algebra is regular and in this paper we give results supporting the conjecture by computing the language of several classes of PI-algebras. Among them, we compute the language generated by some algebras of glued cells that are a useful tool to better understand the so-called Zariski-closed algebras.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"727 ","pages":"Pages 61-83"},"PeriodicalIF":1.1,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828823","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}
{"title":"A hidden variable resultant method for the polynomial multiparameter eigenvalue problem","authors":"Emil Graf, Alex Townsend","doi":"10.1016/j.laa.2025.07.031","DOIUrl":"10.1016/j.laa.2025.07.031","url":null,"abstract":"<div><div>We present a novel, global algorithm for solving polynomial multiparameter eigenvalue problems (PMEPs) by leveraging a hidden variable tensor Dixon resultant framework. Our method transforms a PMEP into one or more univariate polynomial eigenvalue problems, which are solved as generalized eigenvalue problems. Our general approach avoids the need for custom linearizations of PMEPs. We provide rigorous theoretical guarantees for generic PMEPs and give practical strategies for nongeneric systems. Benchmarking on applications from aeroelastic flutter and leaky wave propagation confirms that our algorithm attains high accuracy and robustness while being broadly applicable to many PMEPs.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"727 ","pages":"Pages 37-60"},"PeriodicalIF":1.1,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810385","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}
J. Ignacio Alvarez-Hamelin , Juan I. Giribet , Ignacio Mas , J. Francisco Presenza
{"title":"Extremal properties and bounds for the generalized algebraic connectivity of graphs in Euclidean spaces","authors":"J. Ignacio Alvarez-Hamelin , Juan I. Giribet , Ignacio Mas , J. Francisco Presenza","doi":"10.1016/j.laa.2025.07.028","DOIUrl":"10.1016/j.laa.2025.07.028","url":null,"abstract":"<div><div>This article contributes to the study of graph rigidity and its interplay with fundamental graph invariants. Recently, a quantitative measure of graph rigidity in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span>, termed the generalized algebraic connectivity, was introduced. This development extends the notion of algebraic connectivity—the second-smallest eigenvalue of the Laplacian matrix. In this work, we show that the generalized algebraic connectivity is bounded above by the algebraic connectivity. To capture this relationship, we introduce the <em>d</em>-rigidity ratio, a normalized metric of a graph's rigidity relative to its connectivity. We also investigate the relationship between rigidity and the diameter. In this context, we provide the maximal diameter achievable by rigid graphs and show that generalized path graphs serve as extremal examples. Moreover, we establish a new upper bound for the algebraic connectivity that depends inversely on the diameter and the vertex connectivity. Finally, we derive an upper bound for the algebraic connectivity of generalized path graphs that asymptotically improves existing ones by a factor of four.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"727 ","pages":"Pages 24-36"},"PeriodicalIF":1.1,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810384","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}
{"title":"Symmetries of hypergraphs and some invariant subspaces of matrices associated with hypergraphs","authors":"Anirban Banerjee , Samiron Parui","doi":"10.1016/j.laa.2025.07.030","DOIUrl":"10.1016/j.laa.2025.07.030","url":null,"abstract":"<div><div>Here, the structural symmetries of a hypergraph are represented through equivalence relations on the vertex set of the hypergraph. A matrix associated with the hypergraph may not reflect a specific structural symmetry. In the context of a given symmetry within a hypergraph, we investigate a collection of matrices that encapsulate information about the symmetry. Our investigation reveals that certain structural symmetries in a hypergraph manifest observable effects on the eigenvalues and eigenvectors of designated matrices associated with the hypergraph. We identify specific matrices where the invariance is a consequence of symmetries present in the hypergraph. These invariant subspaces elucidate analogous behaviours observed in certain clusters of vertices during random walks and other dynamical processes on the hypergraph.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"726 ","pages":"Pages 328-358"},"PeriodicalIF":1.1,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144773125","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}
{"title":"Unique continuation principles for finite-element discretizations of the Laplacian","authors":"Graham Cox, Scott MacLachlan, Luke Steeves","doi":"10.1016/j.laa.2025.07.029","DOIUrl":"10.1016/j.laa.2025.07.029","url":null,"abstract":"<div><div>Unique continuation principles are fundamental properties of elliptic partial differential equations, giving conditions that guarantee that the solution to an elliptic equation must be uniformly zero. Since finite-element discretizations are a natural tool to help gain understanding into elliptic equations, it is natural to ask if such principles also hold at the discrete level. In this work, we prove a version of the unique continuation principle for piecewise-linear and -bilinear finite-element discretizations of the Laplacian eigenvalue problem on polygonal domains in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>. Namely, we show that any solution to the discretized equation <span><math><mo>−</mo><mi>Δ</mi><mi>u</mi><mo>=</mo><mi>λ</mi><mi>u</mi></math></span> with vanishing Dirichlet and Neumann traces must be identically zero under certain geometric and topological assumptions on the resulting triangulation. We also provide a counterexample, showing that a nonzero <em>inner solution</em> exists when the topological assumptions are not satisfied. Finally, we give an application to an eigenvalue interlacing problem, where the space of inner solutions makes an explicit appearance.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"727 ","pages":"Pages 84-111"},"PeriodicalIF":1.1,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828824","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}
{"title":"Maximizing the spectral radius of graphs of given size with a forbidden subgraph","authors":"Yanting Zhang , Ligong Wang","doi":"10.1016/j.laa.2025.07.032","DOIUrl":"10.1016/j.laa.2025.07.032","url":null,"abstract":"<div><div>Let <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>7</mn></mrow></msub></math></span> denote the 7-vertex <em>fan graph</em> consisting of a 6-vertex path plus a vertex adjacent to each vertex of the path. Let <span><math><msub><mrow><mi>K</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>∨</mo><mfrac><mrow><mi>m</mi><mo>−</mo><mn>3</mn></mrow><mrow><mn>3</mn></mrow></mfrac><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> be the graph obtained by joining each vertex of a triangle <span><math><msub><mrow><mi>K</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> to <span><math><mfrac><mrow><mi>m</mi><mo>−</mo><mn>3</mn></mrow><mrow><mn>3</mn></mrow></mfrac></math></span> isolated vertices. In this paper, we show that if <em>G</em> is an <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>7</mn></mrow></msub></math></span>-free graph with size <span><math><mi>m</mi><mo>≥</mo><mn>33</mn></math></span>, then the spectral radius <span><math><mi>ρ</mi><mo>(</mo><mi>G</mi><mo>)</mo><mo>≤</mo><mn>1</mn><mo>+</mo><msqrt><mrow><mi>m</mi><mo>−</mo><mn>2</mn></mrow></msqrt></math></span>, equality holds if and only if <span><math><mi>G</mi><mo>≅</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>∨</mo><mfrac><mrow><mi>m</mi><mo>−</mo><mn>3</mn></mrow><mrow><mn>3</mn></mrow></mfrac><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> (possibly, with some isolated vertices).</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"727 ","pages":"Pages 10-23"},"PeriodicalIF":1.1,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810383","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}
Helen Samara Dos Santos , Felipe Yukihide Yasumura
{"title":"Group gradings on finite-dimensional incidence algebras. II","authors":"Helen Samara Dos Santos , Felipe Yukihide Yasumura","doi":"10.1016/j.laa.2025.07.027","DOIUrl":"10.1016/j.laa.2025.07.027","url":null,"abstract":"<div><div>We complete the description of group gradings on finite-dimensional incidence algebras. Moreover, we classify the finite-dimensional graded algebras that can be realized as incidence algebras endowed with a group grading.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"726 ","pages":"Pages 273-290"},"PeriodicalIF":1.1,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144766595","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}
{"title":"Majorizations for probability distributions, column stochastic matrices and their linear preservers","authors":"Pavel Shteyner","doi":"10.1016/j.laa.2025.07.024","DOIUrl":"10.1016/j.laa.2025.07.024","url":null,"abstract":"<div><div>In this paper, we study majorization for probability distributions and column stochastic matrices. We show that majorizations in general can be reduced to the aforementioned sets. We characterize linear operators that preserve majorization for probability distributions, and show their equivalence to operators preserving vector majorization. Our main result provides a complete characterization of linear preservers of strong majorization for column stochastic matrices, revealing a richer structure of preservers than in the standard setting. As a prerequisite to this characterization, we solve the problem of characterizing linear preservers of majorization for zero-sum vectors, which yields a new structural insight into the classical results of Ando and of Li and Poon.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"726 ","pages":"Pages 291-327"},"PeriodicalIF":1.1,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144766596","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}
{"title":"New weighted spectral geometric mean and quantum divergence","authors":"Miran Jeong , Sejong Kim , Tin-Yau Tam","doi":"10.1016/j.laa.2025.07.025","DOIUrl":"10.1016/j.laa.2025.07.025","url":null,"abstract":"<div><div>A new class of weighted spectral geometric means has recently been introduced. In this paper, we present its inequalities in terms of the Löwner order, operator norm, and trace. Moreover, we establish a log-majorization relationship between the new spectral geometric mean and the Rényi relative operator entropy. We also study the quantum divergence of the quantity, given by the difference of trace values between the arithmetic mean and new spectral geometric mean. Finally, we study the barycenter that minimizes the weighted sum of quantum divergences for given variables.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"726 ","pages":"Pages 164-179"},"PeriodicalIF":1.1,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144750354","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}
{"title":"Doubly transitive equiangular tight frames that contain regular simplices","authors":"Matthew Fickus, Evan C. Lake","doi":"10.1016/j.laa.2025.07.023","DOIUrl":"10.1016/j.laa.2025.07.023","url":null,"abstract":"<div><div>An equiangular tight frame (ETF) is a finite sequence of equal norm vectors in a Hilbert space that achieves equality in the Welch bound, and so has minimal coherence. The binder of an ETF is the set of all subsets of its indices whose corresponding vectors form a regular simplex. An ETF achieves equality in Donoho and Elad's spark bound if and only if its binder is nonempty. When this occurs, its binder is the set of all linearly dependent subsets of it of minimal size. Moreover, if members of the binder form a balanced incomplete block design (BIBD) then its incidence matrix can be phased to produce a sparse representation of its dual (Naimark complement). A few infinite families of ETFs are known to have this remarkable property. In this paper, we relate this property to the recently introduced concept of a doubly transitive equiangular tight frame (DTETF), namely an ETF for which the natural action of its symmetry group is doubly transitive. In particular, we show that the binder of any DTETF is either empty or forms a BIBD, and moreover that when the latter occurs, any member of the binder of its dual is an oval of this BIBD. We then apply this general theory to certain known infinite families of DTETFs. Specifically, any symplectic form on a finite vector space yields a DTETF, and we compute the binder of it and its dual, showing that the former is empty except in a single notable case, and that the latter consists of affine Lagrangian subspaces. This unifies and generalizes several results from the existing literature. We then consider the binders of four infinite families of DTETFs that arise from quadratic forms over the field of two elements, showing that two of these are empty except in a finite number of cases, whereas the other two form BIBDs that relate to each other, and to Lagrangian subspaces, in nonobvious ways.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"726 ","pages":"Pages 113-163"},"PeriodicalIF":1.1,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144738686","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}