Pub Date : 2026-04-15Epub Date: 2026-01-13DOI: 10.1016/j.laa.2026.01.012
Lele Liu , Bo Ning
We establish a spectral counterpart to Ore's problem (1962) which asks for the maximum size of an n-vertex graph such that its complement is connected and does not contain as a subgraph, where is a clique of order . Specifically, we characterize the unique graph achieving the maximum spectral radius among all n-vertex, -free graphs with connected complements. The proof strategy combines the association of the extremal graph with an auxiliary tree to infer its structure and technical spectral analysis of the extremal graphs' Perron vector.
{"title":"A spectral analogue of Ore's problem on Turán theorem","authors":"Lele Liu , Bo Ning","doi":"10.1016/j.laa.2026.01.012","DOIUrl":"10.1016/j.laa.2026.01.012","url":null,"abstract":"<div><div>We establish a spectral counterpart to Ore's problem (1962) which asks for the maximum size of an <em>n</em>-vertex graph such that its complement is connected and does not contain <span><math><msub><mrow><mi>K</mi></mrow><mrow><mi>r</mi><mo>+</mo><mn>1</mn></mrow></msub></math></span> as a subgraph, where <span><math><msub><mrow><mi>K</mi></mrow><mrow><mi>r</mi><mo>+</mo><mn>1</mn></mrow></msub></math></span> is a clique of order <span><math><mi>r</mi><mo>+</mo><mn>1</mn></math></span>. Specifically, we characterize the unique graph achieving the maximum spectral radius among all <em>n</em>-vertex, <span><math><msub><mrow><mi>K</mi></mrow><mrow><mi>r</mi><mo>+</mo><mn>1</mn></mrow></msub></math></span>-free graphs with connected complements. The proof strategy combines the association of the extremal graph with an auxiliary tree to infer its structure and technical spectral analysis of the extremal graphs' Perron vector.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"735 ","pages":"Pages 112-122"},"PeriodicalIF":1.1,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036316","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 : 2026-04-15Epub Date: 2026-01-15DOI: 10.1016/j.laa.2026.01.008
Ralph Morrison
We study the commuting graph of matrices over the field of p-adics , whose vertices are non-scalar matrices with entries in and whose edges connect pairs of matrices that commute under matrix multiplication. We prove that this graph is connected if and only if , with n neither prime nor a power of p. We also prove that in the case of and for q a prime with , the commuting graph has the maximum possible diameter of 6; these are the first known such examples independent of the axiom of choice. We also find choices of p and n yielding diameter 4 and diameter 5 commuting graphs, and prove general bounds depending on p and n.
{"title":"Commuting graphs of p-adic matrices","authors":"Ralph Morrison","doi":"10.1016/j.laa.2026.01.008","DOIUrl":"10.1016/j.laa.2026.01.008","url":null,"abstract":"<div><div>We study the commuting graph of <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> matrices over the field of <em>p</em>-adics <span><math><msub><mrow><mi>Q</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>, whose vertices are non-scalar <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> matrices with entries in <span><math><msub><mrow><mi>Q</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> and whose edges connect pairs of matrices that commute under matrix multiplication. We prove that this graph is connected if and only if <span><math><mi>n</mi><mo>≥</mo><mn>3</mn></math></span>, with <em>n</em> neither prime nor a power of <em>p</em>. We also prove that in the case of <span><math><mi>p</mi><mo>=</mo><mn>2</mn></math></span> and <span><math><mi>n</mi><mo>=</mo><mn>2</mn><mi>q</mi></math></span> for <em>q</em> a prime with <span><math><mi>q</mi><mo>≥</mo><mn>7</mn></math></span>, the commuting graph has the maximum possible diameter of 6; these are the first known such examples independent of the axiom of choice. We also find choices of <em>p</em> and <em>n</em> yielding diameter 4 and diameter 5 commuting graphs, and prove general bounds depending on <em>p</em> and <em>n</em>.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"735 ","pages":"Pages 188-202"},"PeriodicalIF":1.1,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036317","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 : 2026-04-15Epub Date: 2026-01-12DOI: 10.1016/j.laa.2026.01.003
Fumio Hiai
In this paper, for , and positive semidefinite matrices A and B, we consider the quasi-extensions of several α-weighted geometric type matrix means such as the α-weighted geometric mean in Kubo–Ando's sense, the Rényi mean, etc. The log-majorization is examined for pairs of those α-weighted geometric type means. The joint concavity/convexity of the trace functions is also discussed based on theory of quantum divergences.
本文对α∈(0,∞)∈{1},p>;0和正半定矩阵A和B,考虑了几个α-加权几何型矩阵均值m - α,p(A,B):= m - α(Ap,Bp)1/p的拟扩展,如Kubo-Ando意义上的α-加权几何均值,rsamnyi均值等。对这些α-加权几何型均值的对(M,N),检验了Mα,p(A,B),q(A,B)的对数化。基于量子散度理论讨论了迹函数TrMα,p的联合凹凸性。
{"title":"Log-majorizations between quasi-geometric type means for matrices","authors":"Fumio Hiai","doi":"10.1016/j.laa.2026.01.003","DOIUrl":"10.1016/j.laa.2026.01.003","url":null,"abstract":"<div><div>In this paper, for <span><math><mi>α</mi><mo>∈</mo><mo>(</mo><mn>0</mn><mo>,</mo><mo>∞</mo><mo>)</mo><mo>∖</mo><mo>{</mo><mn>1</mn><mo>}</mo></math></span>, <span><math><mi>p</mi><mo>></mo><mn>0</mn></math></span> and positive semidefinite matrices <em>A</em> and <em>B</em>, we consider the quasi-extensions <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>α</mi><mo>,</mo><mi>p</mi></mrow></msub><mo>(</mo><mi>A</mi><mo>,</mo><mi>B</mi><mo>)</mo><mo>:</mo><mo>=</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>α</mi></mrow></msub><msup><mrow><mo>(</mo><msup><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msup><mo>,</mo><msup><mrow><mi>B</mi></mrow><mrow><mi>p</mi></mrow></msup><mo>)</mo></mrow><mrow><mn>1</mn><mo>/</mo><mi>p</mi></mrow></msup></math></span> of several <em>α</em>-weighted geometric type matrix means <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>α</mi></mrow></msub><mo>(</mo><mi>A</mi><mo>,</mo><mi>B</mi><mo>)</mo></math></span> such as the <em>α</em>-weighted geometric mean in Kubo–Ando's sense, the Rényi mean, etc. The log-majorization <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>α</mi><mo>,</mo><mi>p</mi></mrow></msub><mo>(</mo><mi>A</mi><mo>,</mo><mi>B</mi><mo>)</mo><msub><mrow><mo>≺</mo></mrow><mrow><mi>log</mi></mrow></msub><msub><mrow><mi>N</mi></mrow><mrow><mi>α</mi><mo>,</mo><mi>q</mi></mrow></msub><mo>(</mo><mi>A</mi><mo>,</mo><mi>B</mi><mo>)</mo></math></span> is examined for pairs <span><math><mo>(</mo><mi>M</mi><mo>,</mo><mi>N</mi><mo>)</mo></math></span> of those <em>α</em>-weighted geometric type means. The joint concavity/convexity of the trace functions <span><math><mrow><mi>Tr</mi></mrow><mspace></mspace><msub><mrow><mi>M</mi></mrow><mrow><mi>α</mi><mo>,</mo><mi>p</mi></mrow></msub></math></span> is also discussed based on theory of quantum divergences.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"735 ","pages":"Pages 123-174"},"PeriodicalIF":1.1,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036321","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 : 2026-04-15Epub Date: 2026-01-20DOI: 10.1016/j.laa.2026.01.019
Qiang Dong , Shunye Li
In this article, we present quiver realizations of two classes of algebras that are derived equivalent to upper triangular matrix algebras. We investigate defective rectangle algebras and show that four of them are derived equivalent. Moreover, we establish derived equivalences between certain defective rectangle algebras and Nakayama algebras.
{"title":"Derived equivalences between defective rectangles","authors":"Qiang Dong , Shunye Li","doi":"10.1016/j.laa.2026.01.019","DOIUrl":"10.1016/j.laa.2026.01.019","url":null,"abstract":"<div><div>In this article, we present quiver realizations of two classes of algebras that are derived equivalent to upper triangular matrix algebras. We investigate defective rectangle algebras and show that four of them are derived equivalent. Moreover, we establish derived equivalences between certain defective rectangle algebras and Nakayama algebras.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"735 ","pages":"Pages 287-306"},"PeriodicalIF":1.1,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036323","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}
<div><div>Suppose <span><math><mi>A</mi><mo>=</mo><mo>[</mo><msub><mrow><mi>a</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub><mo>]</mo><mo>∈</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><mi>C</mi><mo>)</mo></math></span> is a complex <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> matrix and <span><math><mi>B</mi><mo>∈</mo><mi>B</mi><mo>(</mo><mi>H</mi><mo>)</mo></math></span> is a bounded linear operator on a complex Hilbert space <span><math><mi>H</mi></math></span>. We show that <span><math><mi>w</mi><mo>(</mo><mi>A</mi><mo>⊗</mo><mi>B</mi><mo>)</mo><mo>≤</mo><mi>w</mi><mo>(</mo><mi>C</mi><mo>)</mo></math></span>, where <span><math><mi>w</mi><mo>(</mo><mo>⋅</mo><mo>)</mo></math></span> denotes the numerical radius and <span><math><mi>C</mi><mo>=</mo><mo>[</mo><msub><mrow><mi>c</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub><mo>]</mo></math></span> with <span><math><msub><mrow><mi>c</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub><mo>=</mo><mi>w</mi><mrow><mo>(</mo><mrow><mo>[</mo><mtable><mtr><mtd><mn>0</mn></mtd><mtd><msub><mrow><mi>a</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub></mtd></mtr><mtr><mtd><msub><mrow><mi>a</mi></mrow><mrow><mi>j</mi><mi>i</mi></mrow></msub></mtd><mtd><mn>0</mn></mtd></mtr></mtable><mo>]</mo></mrow><mo>⊗</mo><mi>B</mi><mo>)</mo></mrow></math></span>. This refines Holbrook's classical bound <span><math><mi>w</mi><mo>(</mo><mi>A</mi><mo>⊗</mo><mi>B</mi><mo>)</mo><mo>≤</mo><mi>w</mi><mo>(</mo><mi>A</mi><mo>)</mo><mo>‖</mo><mi>B</mi><mo>‖</mo></math></span> (1969) <span><span>[31]</span></span>, when all entries of <em>A</em> are non-negative. If moreover <span><math><msub><mrow><mi>a</mi></mrow><mrow><mi>i</mi><mi>i</mi></mrow></msub><mo>≠</mo><mn>0</mn></math></span> ∀<em>i</em>, we prove that <span><math><mi>w</mi><mo>(</mo><mi>A</mi><mo>⊗</mo><mi>B</mi><mo>)</mo><mo>=</mo><mi>w</mi><mo>(</mo><mi>A</mi><mo>)</mo><mo>‖</mo><mi>B</mi><mo>‖</mo></math></span> if and only if <span><math><mi>w</mi><mo>(</mo><mi>B</mi><mo>)</mo><mo>=</mo><mo>‖</mo><mi>B</mi><mo>‖</mo></math></span>. We then extend these and other results to the more general setting of semi-Hilbertian spaces induced by a positive operator.</div><div>In the reverse direction, we also specialize these results to Kronecker products and hence to Schur/entrywise products, of matrices: (1)(a) We first provide an alternate proof (using <span><math><mi>w</mi><mo>(</mo><mi>A</mi><mo>)</mo></math></span>) of a result of Goldberg and Zwas (1974) <span><span>[24]</span></span> that if the spectral norm of <em>A</em> equals its spectral radius, then each Jordan block for each maximum-modulus eigenvalue must be <span><math><mn>1</mn><mo>×</mo><mn>1</mn></math></span> (“partial diagonalizability”). (b) Using our approach, we further show given <span><math><mi>m</mi><mo>≥</mo><mn>1</mn></math></span> that <span><math><mi>w</mi><mo>(</mo><msup><mrow><mi>A</mi></mrow><mrow><mo>∘</mo><mi>m</mi></mrow></msup><mo>)</mo><mo>
{"title":"Numerical radius and ℓp operator norm of Kronecker products and Schur powers: inequalities and equalities","authors":"Pintu Bhunia , Sujit Sakharam Damase , Apoorva Khare","doi":"10.1016/j.laa.2026.01.005","DOIUrl":"10.1016/j.laa.2026.01.005","url":null,"abstract":"<div><div>Suppose <span><math><mi>A</mi><mo>=</mo><mo>[</mo><msub><mrow><mi>a</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub><mo>]</mo><mo>∈</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><mi>C</mi><mo>)</mo></math></span> is a complex <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> matrix and <span><math><mi>B</mi><mo>∈</mo><mi>B</mi><mo>(</mo><mi>H</mi><mo>)</mo></math></span> is a bounded linear operator on a complex Hilbert space <span><math><mi>H</mi></math></span>. We show that <span><math><mi>w</mi><mo>(</mo><mi>A</mi><mo>⊗</mo><mi>B</mi><mo>)</mo><mo>≤</mo><mi>w</mi><mo>(</mo><mi>C</mi><mo>)</mo></math></span>, where <span><math><mi>w</mi><mo>(</mo><mo>⋅</mo><mo>)</mo></math></span> denotes the numerical radius and <span><math><mi>C</mi><mo>=</mo><mo>[</mo><msub><mrow><mi>c</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub><mo>]</mo></math></span> with <span><math><msub><mrow><mi>c</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub><mo>=</mo><mi>w</mi><mrow><mo>(</mo><mrow><mo>[</mo><mtable><mtr><mtd><mn>0</mn></mtd><mtd><msub><mrow><mi>a</mi></mrow><mrow><mi>i</mi><mi>j</mi></mrow></msub></mtd></mtr><mtr><mtd><msub><mrow><mi>a</mi></mrow><mrow><mi>j</mi><mi>i</mi></mrow></msub></mtd><mtd><mn>0</mn></mtd></mtr></mtable><mo>]</mo></mrow><mo>⊗</mo><mi>B</mi><mo>)</mo></mrow></math></span>. This refines Holbrook's classical bound <span><math><mi>w</mi><mo>(</mo><mi>A</mi><mo>⊗</mo><mi>B</mi><mo>)</mo><mo>≤</mo><mi>w</mi><mo>(</mo><mi>A</mi><mo>)</mo><mo>‖</mo><mi>B</mi><mo>‖</mo></math></span> (1969) <span><span>[31]</span></span>, when all entries of <em>A</em> are non-negative. If moreover <span><math><msub><mrow><mi>a</mi></mrow><mrow><mi>i</mi><mi>i</mi></mrow></msub><mo>≠</mo><mn>0</mn></math></span> ∀<em>i</em>, we prove that <span><math><mi>w</mi><mo>(</mo><mi>A</mi><mo>⊗</mo><mi>B</mi><mo>)</mo><mo>=</mo><mi>w</mi><mo>(</mo><mi>A</mi><mo>)</mo><mo>‖</mo><mi>B</mi><mo>‖</mo></math></span> if and only if <span><math><mi>w</mi><mo>(</mo><mi>B</mi><mo>)</mo><mo>=</mo><mo>‖</mo><mi>B</mi><mo>‖</mo></math></span>. We then extend these and other results to the more general setting of semi-Hilbertian spaces induced by a positive operator.</div><div>In the reverse direction, we also specialize these results to Kronecker products and hence to Schur/entrywise products, of matrices: (1)(a) We first provide an alternate proof (using <span><math><mi>w</mi><mo>(</mo><mi>A</mi><mo>)</mo></math></span>) of a result of Goldberg and Zwas (1974) <span><span>[24]</span></span> that if the spectral norm of <em>A</em> equals its spectral radius, then each Jordan block for each maximum-modulus eigenvalue must be <span><math><mn>1</mn><mo>×</mo><mn>1</mn></math></span> (“partial diagonalizability”). (b) Using our approach, we further show given <span><math><mi>m</mi><mo>≥</mo><mn>1</mn></math></span> that <span><math><mi>w</mi><mo>(</mo><msup><mrow><mi>A</mi></mrow><mrow><mo>∘</mo><mi>m</mi></mrow></msup><mo>)</mo><mo>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"735 ","pages":"Pages 1-30"},"PeriodicalIF":1.1,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145969253","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 : 2026-04-15Epub Date: 2026-01-23DOI: 10.1016/j.laa.2026.01.022
Liwen Zhang, Zhiyuan Zhang
Let be a set of graphs on the same vertex set where is even. We say admits a rainbow k-factor if there exists a k-regular graph F on the vertex set V such that all edges of F are from different members of . In this paper, we show a sufficient spectral condition for the existence of a rainbow k-factor for , which is that if for each , then admits a rainbow k-factor unless .
{"title":"Spectral radius and rainbow k-factors of graphs","authors":"Liwen Zhang, Zhiyuan Zhang","doi":"10.1016/j.laa.2026.01.022","DOIUrl":"10.1016/j.laa.2026.01.022","url":null,"abstract":"<div><div>Let <span><math><mi>G</mi><mo>=</mo><mo>{</mo><msub><mrow><mi>G</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>G</mi></mrow><mrow><mfrac><mrow><mi>k</mi><mi>n</mi></mrow><mrow><mn>2</mn></mrow></mfrac></mrow></msub><mo>}</mo></math></span> be a set of graphs on the same vertex set <span><math><mi>V</mi><mo>=</mo><mo>{</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>n</mi><mo>}</mo></math></span> where <span><math><mi>k</mi><mo>⋅</mo><mi>n</mi></math></span> is even. We say <span><math><mi>G</mi></math></span> admits a rainbow <em>k</em>-factor if there exists a <em>k</em>-regular graph <em>F</em> on the vertex set <em>V</em> such that all edges of <em>F</em> are from different members of <span><math><mi>G</mi></math></span>. In this paper, we show a sufficient spectral condition for the existence of a rainbow <em>k</em>-factor for <span><math><mi>k</mi><mo>≥</mo><mn>2</mn></math></span>, which is that if <span><math><mi>ρ</mi><mo>(</mo><msub><mrow><mi>G</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>)</mo><mo>≥</mo><mi>ρ</mi><mo>(</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>k</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>∨</mo><mo>(</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>∪</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>n</mi><mo>−</mo><mi>k</mi></mrow></msub><mo>)</mo><mo>)</mo></math></span> for each <span><math><msub><mrow><mi>G</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><mi>G</mi></math></span>, then <span><math><mi>G</mi></math></span> admits a rainbow <em>k</em>-factor unless <span><math><msub><mrow><mi>G</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>=</mo><msub><mrow><mi>G</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>=</mo><mo>⋯</mo><mo>=</mo><msub><mrow><mi>G</mi></mrow><mrow><mfrac><mrow><mi>k</mi><mi>n</mi></mrow><mrow><mn>2</mn></mrow></mfrac></mrow></msub><mo>≅</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>k</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>∨</mo><mo>(</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>∪</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>n</mi><mo>−</mo><mi>k</mi></mrow></msub><mo>)</mo></math></span>.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"735 ","pages":"Pages 307-318"},"PeriodicalIF":1.1,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090724","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 : 2026-04-01Epub Date: 2026-01-02DOI: 10.1016/j.laa.2025.12.023
Prem Dagar, Mahendra Kumar Verma
Let F be a non-Archimedean local field and be its ring of integers with ϖ chosen as a fixed generator for the maximal ideal of . Define as the finite local ring. In this paper, we describe the explicit construction of parabolically induced representations of the group for and establish an irreducibility criterion for these representations. Additionally, we determine the number of irreducible constituents in the case of reducibility. Furthermore, we study the primitive cuspidal representations and explore the representations of using the Whittaker and Kirillov model.
设F是一个非阿基米德局部域,O是它的整数环,其中选择π作为O的最大理想的固定发生器。定义O n:=O/ < O n >作为有限局部环。本文给出了群GL2(O)对l >;1的抛物诱导表示的显式构造,并建立了这些表示的不可约准则。此外,我们确定在可还原性的情况下不可还原性成分的数量。此外,我们研究了原始的反转表示,并利用Whittaker和Kirillov模型探索了GL2(O)的表示。
{"title":"On representations of GL2 over finite chain rings","authors":"Prem Dagar, Mahendra Kumar Verma","doi":"10.1016/j.laa.2025.12.023","DOIUrl":"10.1016/j.laa.2025.12.023","url":null,"abstract":"<div><div>Let F be a non-Archimedean local field and <span><math><mi>O</mi></math></span> be its ring of integers with <em>ϖ</em> chosen as a fixed generator for the maximal ideal of <span><math><mi>O</mi></math></span>. Define <span><math><msub><mrow><mi>O</mi></mrow><mrow><mi>ℓ</mi></mrow></msub><mo>:</mo><mo>=</mo><mi>O</mi><mo>/</mo><mo>〈</mo><msup><mrow><mi>ϖ</mi></mrow><mrow><mi>ℓ</mi></mrow></msup><mo>〉</mo></math></span> as the finite local ring. In this paper, we describe the explicit construction of parabolically induced representations of the group <span><math><msub><mrow><mi>GL</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><msub><mrow><mi>O</mi></mrow><mrow><mi>ℓ</mi></mrow></msub><mo>)</mo></math></span> for <span><math><mi>ℓ</mi><mo>></mo><mn>1</mn></math></span> and establish an irreducibility criterion for these representations. Additionally, we determine the number of irreducible constituents in the case of reducibility. Furthermore, we study the primitive cuspidal representations and explore the representations of <span><math><msub><mrow><mi>GL</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><msub><mrow><mi>O</mi></mrow><mrow><mi>ℓ</mi></mrow></msub><mo>)</mo></math></span> using the Whittaker and Kirillov model.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"734 ","pages":"Pages 73-88"},"PeriodicalIF":1.1,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928392","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 : 2026-04-01Epub Date: 2026-01-07DOI: 10.1016/j.laa.2025.12.020
Ivan Shestakov , Ualbai Umirbaev
We study an analogue of the Andreadakis–Johnson filtration for automorphism groups of free algebras and introduce the notion of tangent Lie algebras for certain automorphism groups, defined as subalgebras of the Lie algebra of derivations. We show that, for many classical varieties of algebras, the tangent Lie algebra is contained in the Lie algebra of derivations with constant divergence. We also introduce the concepts of approximately tame and absolutely wild automorphisms of free algebras in arbitrary varieties and employ tangent Lie algebras to investigate their properties. It is shown that nearly all known examples of wild automorphisms of free algebras are absolutely wild, with the notable exceptions of the Nagata and Anick automorphisms. We show that the Bergman automorphism of free matrix algebras of order two is absolutely wild. Furthermore, we prove that free algebras in any variety of polynilpotent Lie algebras–except for the abelian and metabelian varieties–also possess absolutely wild automorphisms.
{"title":"Tangent Lie algebras of automorphism groups of free algebras","authors":"Ivan Shestakov , Ualbai Umirbaev","doi":"10.1016/j.laa.2025.12.020","DOIUrl":"10.1016/j.laa.2025.12.020","url":null,"abstract":"<div><div>We study an analogue of the Andreadakis–Johnson filtration for automorphism groups of free algebras and introduce the notion of tangent Lie algebras for certain automorphism groups, defined as subalgebras of the Lie algebra of derivations. We show that, for many classical varieties of algebras, the tangent Lie algebra is contained in the Lie algebra of derivations with constant divergence. We also introduce the concepts of approximately tame and absolutely wild automorphisms of free algebras in arbitrary varieties and employ tangent Lie algebras to investigate their properties. It is shown that nearly all known examples of wild automorphisms of free algebras are absolutely wild, with the notable exceptions of the Nagata and Anick automorphisms. We show that the Bergman automorphism of free matrix algebras of order two is absolutely wild. Furthermore, we prove that free algebras in any variety of polynilpotent Lie algebras–except for the abelian and metabelian varieties–also possess absolutely wild automorphisms.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"734 ","pages":"Pages 193-223"},"PeriodicalIF":1.1,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979684","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 : 2026-04-01Epub Date: 2026-01-05DOI: 10.1016/j.laa.2025.12.019
Ming-Cheng Tsai , Huajun Huang
We characterize maps , and , that have the multiplicative spectrum or trace preserving property: where is the set of doubly stochastic, row stochastic, or column stochastic matrices, or the space spanned by one of these sets. Linearity is assumed when . We show that every stochastic matrix contains a real doubly stochastic component that carries the spectral information. In consequence, the multiplicative spectrum or trace preservers on these sets are linked to the corresponding preservers on the space of doubly stochastic matrices. Moreover, when , multiplicative trace preservers always coincide with multiplicative spectrum preservers.
{"title":"Multiplicative trace and spectrum preservers on stochastic matrices","authors":"Ming-Cheng Tsai , Huajun Huang","doi":"10.1016/j.laa.2025.12.019","DOIUrl":"10.1016/j.laa.2025.12.019","url":null,"abstract":"<div><div>We characterize maps <span><math><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>:</mo><mi>S</mi><mo>→</mo><mi>S</mi></math></span>, <span><math><mi>i</mi><mo>=</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>m</mi></math></span> and <span><math><mi>m</mi><mo>≥</mo><mn>1</mn></math></span>, that have the multiplicative spectrum or trace preserving property:<span><span><span><math><mi>spec</mi><mo>(</mo><msub><mrow><mi>ϕ</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>)</mo><mo>⋯</mo><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>)</mo><mo>)</mo><mo>=</mo><mi>spec</mi><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>⋯</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>)</mo><mo>,</mo><mspace></mspace><mtext>or</mtext><mspace></mspace><mi>tr</mi><mo>(</mo><msub><mrow><mi>ϕ</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>)</mo><mo>⋯</mo><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>)</mo><mo>)</mo><mo>=</mo><mi>tr</mi><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>⋯</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>)</mo><mo>,</mo></math></span></span></span> where <span><math><mi>S</mi></math></span> is the set of <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> doubly stochastic, row stochastic, or column stochastic matrices, or the space spanned by one of these sets. Linearity is assumed when <span><math><mi>m</mi><mo>=</mo><mn>1</mn></math></span>. We show that every stochastic matrix contains a real doubly stochastic component that carries the spectral information. In consequence, the multiplicative spectrum or trace preservers on these sets <span><math><mi>S</mi></math></span> are linked to the corresponding preservers on the space of doubly stochastic matrices. Moreover, when <span><math><mi>m</mi><mo>≥</mo><mn>3</mn></math></span>, multiplicative trace preservers always coincide with multiplicative spectrum preservers.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"734 ","pages":"Pages 118-151"},"PeriodicalIF":1.1,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979681","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 : 2026-04-01Epub Date: 2026-01-02DOI: 10.1016/j.laa.2025.12.021
Emily J. King , Dustin G. Mixon , Shayne Waldron
Given two tuples of subspaces, can you tell whether the tuples are isomorphic? We develop theory and algorithms to address this fundamental question. We focus on isomorphisms in which the ambient vector space is acted on by either a unitary group or general linear group. If isomorphism also allows permutations of the subspaces, then the problem is at least as hard as graph isomorphism. Otherwise, we provide a variety of polynomial-time algorithms with Matlab implementations to test for isomorphism.
{"title":"Testing isomorphism between tuples of subspaces","authors":"Emily J. King , Dustin G. Mixon , Shayne Waldron","doi":"10.1016/j.laa.2025.12.021","DOIUrl":"10.1016/j.laa.2025.12.021","url":null,"abstract":"<div><div>Given two tuples of subspaces, can you tell whether the tuples are isomorphic? We develop theory and algorithms to address this fundamental question. We focus on isomorphisms in which the ambient vector space is acted on by either a unitary group or general linear group. If isomorphism also allows permutations of the subspaces, then the problem is at least as hard as graph isomorphism. Otherwise, we provide a variety of polynomial-time algorithms with Matlab implementations to test for isomorphism.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"734 ","pages":"Pages 50-72"},"PeriodicalIF":1.1,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928391","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}