Pub Date : 2024-11-19DOI: 10.1016/j.laa.2024.11.012
Weng Kun Sio, Che-Man Cheng
A conjecture from the distillability of quantum entanglement is that when A and B are trace zero complex matrices and (where is the Frobenius norm), the sum of squares of the largest two singular values of does not exceed 1/2. In this paper, the conjecture is proved when
(i)
A or B is unitarily similar to a direct sum of trace zero matrices;
(ii)
A and B are unitarily similar to matrices, when partitioned into blocks, having zero diagonal blocks.
量子纠缠的可提炼性的一个猜想是:当 A 和 B 是 4×4 痕量为零的复矩阵且‖A‖2+‖B‖2=1/4(其中‖⋅‖是弗罗贝尼斯规范)时,A⊗I4+I4⊗B 的最大两个奇异值的平方和不超过 1/2 。本文证明了以下猜想:(i) A 或 B 与 2×2 痕零矩阵的直接和具有单位相似性;(ii) A 和 B 被分割成 2×2 块时与矩阵具有单位相似性,且对角块为零。
{"title":"A note on a conjecture from distillability of quantum entanglement","authors":"Weng Kun Sio, Che-Man Cheng","doi":"10.1016/j.laa.2024.11.012","DOIUrl":"10.1016/j.laa.2024.11.012","url":null,"abstract":"<div><div>A conjecture from the distillability of quantum entanglement is that when <em>A</em> and <em>B</em> are <span><math><mn>4</mn><mo>×</mo><mn>4</mn></math></span> trace zero complex matrices and <span><math><msup><mrow><mo>‖</mo><mi>A</mi><mo>‖</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>+</mo><msup><mrow><mo>‖</mo><mi>B</mi><mo>‖</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>1</mn><mo>/</mo><mn>4</mn></math></span> (where <span><math><mo>‖</mo><mo>⋅</mo><mo>‖</mo></math></span> is the Frobenius norm), the sum of squares of the largest two singular values of <span><math><mi>A</mi><mo>⊗</mo><msub><mrow><mi>I</mi></mrow><mrow><mn>4</mn></mrow></msub><mo>+</mo><msub><mrow><mi>I</mi></mrow><mrow><mn>4</mn></mrow></msub><mo>⊗</mo><mi>B</mi></math></span> does not exceed 1/2. In this paper, the conjecture is proved when<ul><li><span>(i)</span><span><div><em>A</em> or <em>B</em> is unitarily similar to a direct sum of <span><math><mn>2</mn><mo>×</mo><mn>2</mn></math></span> trace zero matrices;</div></span></li><li><span>(ii)</span><span><div><em>A</em> and <em>B</em> are unitarily similar to matrices, when partitioned into <span><math><mn>2</mn><mo>×</mo><mn>2</mn></math></span> blocks, having zero diagonal blocks.</div></span></li></ul></div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"707 ","pages":"Pages 152-161"},"PeriodicalIF":1.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722542","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 : 2024-11-19DOI: 10.1016/j.laa.2024.11.014
Martin Buck, Kasso A. Okoudjou
A graph short-time Fourier transform is defined using the eigenvectors of the graph Laplacian and a graph heat kernel as a window parametrized by a nonnegative time parameter t. We show that the corresponding Gabor-like system forms a frame for and gives a description of the spectrum of the corresponding frame operator in terms of the graph heat kernel and the spectrum of the underlying graph Laplacian. For two classes of algebraic graphs, we prove the frame is tight and independent of the window parameter t.
我们利用图拉普拉卡的特征向量和图热核定义了图短时傅立叶变换,并将其作为由非负时间参数 t 参数化的窗口。我们证明了相应的类 Gabor 系统形成了 Cd 的框架,并用图热核和底层图拉普拉卡的频谱描述了相应框架算子的频谱。对于两类代数图,我们证明了框架是紧密的,且与窗口参数 t 无关。
{"title":"Tight frames generated by a graph short-time Fourier transform","authors":"Martin Buck, Kasso A. Okoudjou","doi":"10.1016/j.laa.2024.11.014","DOIUrl":"10.1016/j.laa.2024.11.014","url":null,"abstract":"<div><div>A <em>graph short-time Fourier transform</em> is defined using the eigenvectors of the graph Laplacian and a graph heat kernel as a window parametrized by a nonnegative time parameter <em>t</em>. We show that the corresponding Gabor-like system forms a frame for <span><math><msup><mrow><mi>C</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> and gives a description of the spectrum of the corresponding frame operator in terms of the graph heat kernel and the spectrum of the underlying graph Laplacian. For two classes of algebraic graphs, we prove the frame is tight and independent of the window parameter <em>t</em>.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"707 ","pages":"Pages 107-125"},"PeriodicalIF":1.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707118","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 : 2024-11-19DOI: 10.1016/j.laa.2024.11.009
Cosimo Flavi
We establish an upper bound for the rank of every power of an arbitrary quadratic form. Specifically, for any , we prove that the s-th power of a quadratic form of rank n grows as . Furthermore, we demonstrate that its rank is subgeneric for all .
我们为任意二次函数形式的每个幂的秩建立了一个上限。具体来说,对于任意 s∈N,我们证明秩为 n 的二次函数形式的 s 次幂随 ns 增长。此外,我们还证明了对于所有 n>(2s-1)2,它的秩都是子代的。
{"title":"Upper bounds for the rank of powers of quadrics","authors":"Cosimo Flavi","doi":"10.1016/j.laa.2024.11.009","DOIUrl":"10.1016/j.laa.2024.11.009","url":null,"abstract":"<div><div>We establish an upper bound for the rank of every power of an arbitrary quadratic form. Specifically, for any <span><math><mi>s</mi><mo>∈</mo><mi>N</mi></math></span>, we prove that the <em>s</em>-th power of a quadratic form of rank <em>n</em> grows as <span><math><msup><mrow><mi>n</mi></mrow><mrow><mi>s</mi></mrow></msup></math></span>. Furthermore, we demonstrate that its rank is subgeneric for all <span><math><mi>n</mi><mo>></mo><msup><mrow><mo>(</mo><mn>2</mn><mi>s</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msup></math></span>.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"707 ","pages":"Pages 49-79"},"PeriodicalIF":1.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142706749","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 : 2024-11-17DOI: 10.1016/j.laa.2024.11.010
Yu Chen
We determine all irreducible real and complex matrix representations of quaternions and classify them up to equivalence. More over, we show that there is a one-to-one correspondence between the equivalence classes of the irreducible matrix representations and those of the field homomorphisms from the real numbers to the complex numbers.
{"title":"Irreducible matrix representations of quaternions","authors":"Yu Chen","doi":"10.1016/j.laa.2024.11.010","DOIUrl":"10.1016/j.laa.2024.11.010","url":null,"abstract":"<div><div>We determine all irreducible real and complex matrix representations of quaternions and classify them up to equivalence. More over, we show that there is a one-to-one correspondence between the equivalence classes of the irreducible matrix representations and those of the field homomorphisms from the real numbers to the complex numbers.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"706 ","pages":"Pages 55-69"},"PeriodicalIF":1.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142699044","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 : 2024-11-16DOI: 10.1016/j.laa.2024.11.013
Ilja Gogić, Mateo Tomašević
We consider subalgebras of the algebra of complex matrices that contain all diagonal matrices, known in the literature as the structural matrix algebras (SMAs).
Let be an arbitrary SMA. We first show that any commuting family of diagonalizable matrices in can be intrinsically simultaneously diagonalized (i.e. the corresponding similarity can be chosen from ). Using this, we then characterize when one SMA Jordan-embeds into another and in that case we describe the form of such Jordan embeddings. As a consequence, we obtain a description of Jordan automorphisms of SMAs, generalizing Coelho's result on their algebra automorphisms. Next, motivated by the results of Marcus-Moyls and Molnar-Šemrl, connecting the linear rank-one preservers with Jordan embeddings and (where is the algebra of upper-triangular matrices) respectively, we show that any linear unital rank-one preserver is necessarily a Jordan embedding. As the converse fails in general, we also provide a necessary and sufficient condition for when it does hold true. Finally, we obtain a complete description of linear rank preservers , as maps of the form , for some invertible matrices and a central idempotent .
我们考虑的是包含所有对角矩阵的 n×n 复矩阵代数 Mn 的子代数 A,文献称之为结构矩阵代数(SMA)。我们首先证明,A 中任何可对角化矩阵的换向族都可以内在地同时对角化(即可以从 A 中选择相应的相似性)。利用这一点,我们可以描述一个 SMA 乔丹嵌入到另一个 SMA 中的情况,并在这种情况下描述这种乔丹嵌入的形式。因此,我们得到了对 SMA 的乔丹自动形的描述,推广了科埃略关于其代数自动形的结果。接下来,受马库斯-莫伊尔斯和莫尔纳-舍姆尔的结果的启发,我们分别将线性秩一预言器与乔丹嵌入 Mn→Mn 和 Tn→Mn (其中 Tn 是 n×n 上三角矩阵代数)联系起来,证明任何线性单元秩一预言器 A→Mn 必然是一个乔丹嵌入。由于反向一般不成立,我们还提供了一个必要条件和充分条件来说明何时反向成立。最后,对于一些可逆矩阵 S,T∈Mn 和一个中心幂等 P∈A,我们得到了线性秩预言器 A→Mn 的完整描述,即形式为 X↦S(PX+(I-P)Xt)T 的映射。
{"title":"Jordan embeddings and linear rank preservers of structural matrix algebras","authors":"Ilja Gogić, Mateo Tomašević","doi":"10.1016/j.laa.2024.11.013","DOIUrl":"10.1016/j.laa.2024.11.013","url":null,"abstract":"<div><div>We consider subalgebras <span><math><mi>A</mi></math></span> of the algebra <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> of <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> complex matrices that contain all diagonal matrices, known in the literature as the structural matrix algebras (SMAs).</div><div>Let <span><math><mi>A</mi><mo>⊆</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> be an arbitrary SMA. We first show that any commuting family of diagonalizable matrices in <span><math><mi>A</mi></math></span> can be intrinsically simultaneously diagonalized (i.e. the corresponding similarity can be chosen from <span><math><mi>A</mi></math></span>). Using this, we then characterize when one SMA Jordan-embeds into another and in that case we describe the form of such Jordan embeddings. As a consequence, we obtain a description of Jordan automorphisms of SMAs, generalizing Coelho's result on their algebra automorphisms. Next, motivated by the results of Marcus-Moyls and Molnar-Šemrl, connecting the linear rank-one preservers with Jordan embeddings <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>→</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>→</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> (where <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> is the algebra of <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> upper-triangular matrices) respectively, we show that any linear unital rank-one preserver <span><math><mi>A</mi><mo>→</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> is necessarily a Jordan embedding. As the converse fails in general, we also provide a necessary and sufficient condition for when it does hold true. Finally, we obtain a complete description of linear rank preservers <span><math><mi>A</mi><mo>→</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>, as maps of the form <span><math><mi>X</mi><mo>↦</mo><mi>S</mi><mrow><mo>(</mo><mi>P</mi><mi>X</mi><mo>+</mo><mo>(</mo><mi>I</mi><mo>−</mo><mi>P</mi><mo>)</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>t</mi></mrow></msup><mo>)</mo></mrow><mi>T</mi></math></span>, for some invertible matrices <span><math><mi>S</mi><mo>,</mo><mi>T</mi><mo>∈</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> and a central idempotent <span><math><mi>P</mi><mo>∈</mo><mi>A</mi></math></span>.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"707 ","pages":"Pages 1-48"},"PeriodicalIF":1.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707119","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 : 2024-11-14DOI: 10.1016/j.laa.2024.11.007
Tanvi Jain , Kirti Kajla
The symplectic inner product on is the sesquilinear form given by where is the real skew-symmetric, orthogonal block matrix . We derive results analogous to the spectral theorem and singular value decomposition for complex matrices such as Hamiltonian and J-normal matrices, in the sesquilinear symplectic inner product spaces.
{"title":"Matrix diagonalisation in sesquilinear symplectic spaces","authors":"Tanvi Jain , Kirti Kajla","doi":"10.1016/j.laa.2024.11.007","DOIUrl":"10.1016/j.laa.2024.11.007","url":null,"abstract":"<div><div>The symplectic inner product on <span><math><msup><mrow><mi>C</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msup></math></span> is the sesquilinear form given by<span><span><span><math><mo>[</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>]</mo><mo>=</mo><mo>〈</mo><mi>x</mi><mo>,</mo><msub><mrow><mi>J</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mi>y</mi><mo>〉</mo><mo>,</mo></math></span></span></span> where <span><math><msub><mrow><mi>J</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub></math></span> is the real skew-symmetric, orthogonal <span><math><mn>2</mn><mo>×</mo><mn>2</mn></math></span> block matrix <span><math><mo>[</mo><mtable><mtr><mtd><mn>0</mn></mtd><mtd><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub></mtd></mtr><mtr><mtd><mo>−</mo><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub></mtd><mtd><mn>0</mn></mtd></mtr></mtable><mo>]</mo></math></span>. We derive results analogous to the spectral theorem and singular value decomposition for complex matrices such as Hamiltonian and <em>J</em>-normal matrices, in the sesquilinear symplectic inner product spaces.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"706 ","pages":"Pages 1-23"},"PeriodicalIF":1.0,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698308","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 : 2024-11-14DOI: 10.1016/j.laa.2024.11.008
M. Bogoya , A. Böttcher , S.M. Grudsky
We consider Hermitian Toeplitz matrices emerging from finite linear combinations with non-negative coefficients of the differential operators over the interval after discretizing them on a uniform grid of step size . The collective distribution in the Szegő–Weyl sense of the eigenvalues of these matrices as n goes to infinity can be described by GLT theory. However, we focus on the asymptotic behavior of the individual eigenvalues, on both the inner eigenvalues in the bulk and on the extreme eigenvalues. The difficulty of the problem is that not only the order of the matrices depends on n but also their so-called symbols. Our main results are third order asymptotic formulas for the eigenvalues in the case . These results reveal some basic phenomena one should expect when considering the problem in full generality.
{"title":"Eigenvalues of Toeplitz matrices emerging from finite differences for certain ordinary differential operators","authors":"M. Bogoya , A. Böttcher , S.M. Grudsky","doi":"10.1016/j.laa.2024.11.008","DOIUrl":"10.1016/j.laa.2024.11.008","url":null,"abstract":"<div><div>We consider Hermitian Toeplitz matrices emerging from finite linear combinations with non-negative coefficients of the differential operators <span><math><msup><mrow><mo>(</mo><mo>−</mo><mn>1</mn><mo>)</mo></mrow><mrow><mi>k</mi></mrow></msup><msup><mrow><mi>d</mi></mrow><mrow><mn>2</mn><mi>k</mi></mrow></msup><mo>/</mo><mi>d</mi><msup><mrow><mi>x</mi></mrow><mrow><mn>2</mn><mi>k</mi></mrow></msup></math></span> over the interval <span><math><mo>(</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>)</mo></math></span> after discretizing them on a uniform grid of step size <span><math><mn>1</mn><mo>/</mo><mo>(</mo><mi>n</mi><mo>+</mo><mn>1</mn><mo>)</mo></math></span>. The collective distribution in the Szegő–Weyl sense of the eigenvalues of these matrices as <em>n</em> goes to infinity can be described by GLT theory. However, we focus on the asymptotic behavior of the individual eigenvalues, on both the inner eigenvalues in the bulk and on the extreme eigenvalues. The difficulty of the problem is that not only the order of the matrices depends on <em>n</em> but also their so-called symbols. Our main results are third order asymptotic formulas for the eigenvalues in the case <span><math><mi>k</mi><mo>⩽</mo><mn>2</mn></math></span>. These results reveal some basic phenomena one should expect when considering the problem in full generality.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"706 ","pages":"Pages 24-54"},"PeriodicalIF":1.0,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698307","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 : 2024-11-13DOI: 10.1016/j.laa.2024.11.006
Xiaoxiao Ma , Yingqing Xiao , Zhao Yang
In this paper, we consider how to accurately solve the product eigenvalue problem for the class of sign regular (SR) matrices with signature and the class of totally nonnegative (TN) matrices, which tend to be extremely ill-conditioned. We present algorithms with complexity to accurately compute the parameter matrices of products of TN matrices and SR matrices with signature . Based on the accurate parameter matrices, all eigenvalues of the product matrix are computed to high relative accuracy. Numerical experiments are provided to confirm the claimed high relative accuracy.
{"title":"Computing eigenvalues for products of two classes of sign regular matrices to high relative accuracy","authors":"Xiaoxiao Ma , Yingqing Xiao , Zhao Yang","doi":"10.1016/j.laa.2024.11.006","DOIUrl":"10.1016/j.laa.2024.11.006","url":null,"abstract":"<div><div>In this paper, we consider how to accurately solve the product eigenvalue problem for the class of sign regular (SR) matrices with signature <span><math><mo>(</mo><mn>1</mn><mo>,</mo><mo>⋯</mo><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>)</mo></math></span> and the class of totally nonnegative (TN) matrices, which tend to be extremely ill-conditioned. We present algorithms with <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>)</mo></math></span> complexity to accurately compute the parameter matrices of products of TN matrices and SR matrices with signature <span><math><mo>(</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>)</mo></math></span>. Based on the accurate parameter matrices, all eigenvalues of the product matrix are computed to high relative accuracy. Numerical experiments are provided to confirm the claimed high relative accuracy.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"707 ","pages":"Pages 80-106"},"PeriodicalIF":1.0,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142706748","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 : 2024-11-07DOI: 10.1016/j.laa.2024.11.005
Rounak Biswas, Falguni Roy
For two idempotent matrix , let alg denote the smallest subalgebra of that contains and the identity matrix . This paper provides a complete classification of alg without imposing any restrictions on P and Q. As a result of this classification, the issue of group invertibility within alg is fully resolved.
对于两个幂等矩阵 P,Q∈Cn×n, 让 alg(In,P,Q) 表示 Cn×n 中包含 P,Q 和同一矩阵 In 的最小子代数。本文在不对 P 和 Q 施加任何限制的情况下,对 alg(In,P,Q) 进行了完整的分类。
{"title":"Comprehensive classification of the algebra generated by two idempotent matrices","authors":"Rounak Biswas, Falguni Roy","doi":"10.1016/j.laa.2024.11.005","DOIUrl":"10.1016/j.laa.2024.11.005","url":null,"abstract":"<div><div>For two idempotent matrix <span><math><mi>P</mi><mo>,</mo><mi>Q</mi><mo>∈</mo><msup><mrow><mi>C</mi></mrow><mrow><mi>n</mi><mo>×</mo><mi>n</mi></mrow></msup></math></span>, let alg<span><math><mo>(</mo><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>,</mo><mi>P</mi><mo>,</mo><mi>Q</mi><mo>)</mo></math></span> denote the smallest subalgebra of <span><math><msup><mrow><mi>C</mi></mrow><mrow><mi>n</mi><mo>×</mo><mi>n</mi></mrow></msup></math></span> that contains <span><math><mi>P</mi><mo>,</mo><mi>Q</mi></math></span> and the identity matrix <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>. This paper provides a complete classification of alg<span><math><mo>(</mo><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>,</mo><mi>P</mi><mo>,</mo><mi>Q</mi><mo>)</mo></math></span> without imposing any restrictions on <em>P</em> and <em>Q</em>. As a result of this classification, the issue of group invertibility within alg<span><math><mo>(</mo><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>,</mo><mi>P</mi><mo>,</mo><mi>Q</mi><mo>)</mo></math></span> is fully resolved.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"705 ","pages":"Pages 185-206"},"PeriodicalIF":1.0,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653347","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 : 2024-11-07DOI: 10.1016/j.laa.2024.11.002
Francesca Albertini , Domenico D'Alessandro
In the analysis of controllability of finite dimensional quantum systems, subspace controllability refers to the situation where the underlying Hilbert space splits into the direct sum of invariant subspaces, and, on each of such invariant subspaces, it is possible to generate any arbitrary unitary operation using appropriate control functions. This is a typical situation in the presence of symmetries for the dynamics.
We investigate whether and when if subspace controllability is verified, the addition of an extra Hamiltonian to the dynamics implies full controllability of the system. Under the natural (and necessary) condition that the new Hamiltonian connects all the invariant subspaces, we show that this is always the case, except for a very specific case we shall describe. Even in this specific case, a weaker notion of controllability, controllability of the state (Pure State Controllability) is verified.
{"title":"Quantum subspace controllability implying full controllability","authors":"Francesca Albertini , Domenico D'Alessandro","doi":"10.1016/j.laa.2024.11.002","DOIUrl":"10.1016/j.laa.2024.11.002","url":null,"abstract":"<div><div>In the analysis of controllability of finite dimensional quantum systems, <em>subspace controllability</em> refers to the situation where the underlying Hilbert space splits into the direct sum of invariant subspaces, and, on each of such invariant subspaces, it is possible to generate any arbitrary unitary operation using appropriate control functions. This is a typical situation in the presence of symmetries for the dynamics.</div><div>We investigate whether and when if subspace controllability is verified, the addition of an extra Hamiltonian to the dynamics implies full controllability of the system. Under the natural (and necessary) condition that the new Hamiltonian connects all the invariant subspaces, we show that this is always the case, except for a very specific case we shall describe. Even in this specific case, a weaker notion of controllability, controllability of the state (<em>Pure State Controllability</em>) is verified.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"705 ","pages":"Pages 207-229"},"PeriodicalIF":1.0,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653348","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}