首页 > 最新文献

Expositiones Mathematicae最新文献

英文 中文
On Miyanishi conjecture for quasi-projective varieties 拟射影变异体的Miyanishi猜想
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-06-17 DOI: 10.1016/j.exmath.2025.125710
Takumi Asano
Miyanishi conjecture claims that for any variety over an algebraically closed field of characteristic zero, any endomorphism of such a variety which is injective outside a closed subset of codimension at least 2 is bijective. We prove Miyanishi conjecture for any quasi-projective variety X which is a dense open subset of a Q-factorial normal projective variety X¯ such that codim(X¯X)2 with the ample canonical divisor or the ample anti-canonical divisor. Also, we observe Miyanishi conjecture without the conditions of its canonical divisor by using minimal model program. In particular, we prove Miyanishi conjecture in the case that X¯ has canonical singularities and X¯ has the canonical model which is obtained by divisorial contractions.
Miyanishi猜想认为,对于特征为0的代数闭域上的任何变体,在余维数至少为2的闭子集外内射的任何自同态是双射的。对于任意拟射影簇X证明了Miyanishi猜想,该拟射影簇X是一个q !正规射影簇X¯的稠密开子集,使得codim(X¯∈X)≥2具有充足的正则除数或充足的反正则除数。此外,我们还利用极小模型程序观察了没有正则约数条件的Miyanishi猜想。特别地,我们证明了在X¯具有正则奇点且X¯具有由分缩得到的正则模型的情况下,Miyanishi猜想。
{"title":"On Miyanishi conjecture for quasi-projective varieties","authors":"Takumi Asano","doi":"10.1016/j.exmath.2025.125710","DOIUrl":"10.1016/j.exmath.2025.125710","url":null,"abstract":"<div><div>Miyanishi conjecture claims that for any variety over an algebraically closed field of characteristic zero, any endomorphism of such a variety which is injective outside a closed subset of codimension at least 2 is bijective. We prove Miyanishi conjecture for any quasi-projective variety <span><math><mi>X</mi></math></span> which is a dense open subset of a <span><math><mi>Q</mi></math></span>-factorial normal projective variety <span><math><mover><mrow><mi>X</mi></mrow><mo>¯</mo></mover></math></span> such that <span><math><mrow><mo>codim</mo><mrow><mo>(</mo><mover><mrow><mi>X</mi></mrow><mo>¯</mo></mover><mo>∖</mo><mi>X</mi><mo>)</mo></mrow><mo>≥</mo><mn>2</mn></mrow></math></span> with the ample canonical divisor or the ample anti-canonical divisor. Also, we observe Miyanishi conjecture without the conditions of its canonical divisor by using minimal model program. In particular, we prove Miyanishi conjecture in the case that <span><math><mover><mrow><mi>X</mi></mrow><mo>¯</mo></mover></math></span> has canonical singularities and <span><math><mover><mrow><mi>X</mi></mrow><mo>¯</mo></mover></math></span> has the canonical model which is obtained by divisorial contractions.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 5","pages":"Article 125710"},"PeriodicalIF":0.8,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On real-valued functions of Lipschitz type 关于Lipschitz型实值函数
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-06-13 DOI: 10.1016/j.exmath.2025.125701
Valentin Gutev
The classical McShane–Whitney extension theorem for Lipschitz functions is refined by showing that for a closed subset of the domain, it remains valid for any interval of the real line. This result is also extended to the setting of locally (pointwise) Lipschitz functions. In contrast to Lipschitz and pointwise Lipschitz extensions, the construction of locally Lipschitz extensions is based on Lipschitz partitions of unity of countable open covers of the domain. Such partitions of unity are a special case of a more general result obtained by Zdeněk Frolík. To avoid the use of Stone’s theorem (paracompactness of metrizable spaces), it is given a simple direct proof of this special case of Frolík’s result. As an application, it is shown that the locally Lipschitz functions are precisely the locally finite sums of sequences of Lipschitz functions. Also, it is obtained a natural locally Lipschitz version of one of Michael’s selection theorems.
对Lipschitz函数的经典McShane-Whitney扩展定理进行了改进,证明了对于定域的一个闭子集,它对实线的任何区间都是有效的。这一结果也推广到局部(点方向)Lipschitz函数的设置。与Lipschitz扩展和点向Lipschitz扩展不同,局部Lipschitz扩展的构造是基于域的可数开盖统一的Lipschitz划分。这种统一分割是zdenk Frolík得到的更一般结果的一种特殊情况。为了避免使用斯通定理(可度量空间的副紧性),给出了Frolík结果的这种特殊情况的简单直接证明。作为一个应用,证明了局部Lipschitz函数正是Lipschitz函数序列的局部有限和。同时,得到了Michael选择定理的一个自然局部Lipschitz版本。
{"title":"On real-valued functions of Lipschitz type","authors":"Valentin Gutev","doi":"10.1016/j.exmath.2025.125701","DOIUrl":"10.1016/j.exmath.2025.125701","url":null,"abstract":"<div><div>The classical McShane–Whitney extension theorem for Lipschitz functions is refined by showing that for a closed subset of the domain, it remains valid for any interval of the real line. This result is also extended to the setting of locally (pointwise) Lipschitz functions. In contrast to Lipschitz and pointwise Lipschitz extensions, the construction of locally Lipschitz extensions is based on Lipschitz partitions of unity of countable open covers of the domain. Such partitions of unity are a special case of a more general result obtained by Zdeněk Frolík. To avoid the use of Stone’s theorem (paracompactness of metrizable spaces), it is given a simple direct proof of this special case of Frolík’s result. As an application, it is shown that the locally Lipschitz functions are precisely the locally finite sums of sequences of Lipschitz functions. Also, it is obtained a natural locally Lipschitz version of one of Michael’s selection theorems.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 5","pages":"Article 125701"},"PeriodicalIF":0.8,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
New variational arguments regarding the Blaschke–Lebesgue theorem 关于Blaschke-Lebesgue定理的新变分论证
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-05-21 DOI: 10.1016/j.exmath.2025.125700
Beniamin Bogosel
The sensitivity of the areas of Reuleaux polygons and disk polygons is computed with respect to vertex perturbations. Computations are completed for both constrained and Lagrangian formulations and they imply that the only critical Reuleaux polygons for the area functional are the regular ones. As a consequence, new variational proofs for the Blaschke–Lebesgue and Firey–Sallee theorems are found.
计算了勒洛多边形和盘形多边形的面积对顶点扰动的敏感性。完成了约束和拉格朗日公式的计算,它们表明面积泛函的唯一关键勒洛多边形是规则多边形。结果,找到了Blaschke-Lebesgue定理和Firey-Sallee定理的新的变分证明。
{"title":"New variational arguments regarding the Blaschke–Lebesgue theorem","authors":"Beniamin Bogosel","doi":"10.1016/j.exmath.2025.125700","DOIUrl":"10.1016/j.exmath.2025.125700","url":null,"abstract":"<div><div>The sensitivity of the areas of Reuleaux polygons and disk polygons is computed with respect to vertex perturbations. Computations are completed for both constrained and Lagrangian formulations and they imply that the only critical Reuleaux polygons for the area functional are the regular ones. As a consequence, new variational proofs for the Blaschke–Lebesgue and Firey–Sallee theorems are found.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 5","pages":"Article 125700"},"PeriodicalIF":0.8,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144115481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Ends and end cohomology 端和端上同调
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-04-21 DOI: 10.1016/j.exmath.2025.125692
William G. Bass, Jack S. Calcut
Ends and end cohomology are powerful invariants for the study of noncompact spaces. We present a self-contained exposition of the topological theory of ends and prove novel extensions including the existence of an exhaustion of a proper map. We define reduced end cohomology as the relative end cohomology of a ray-based space. We use those results to prove a version of a theorem of King that computes the reduced end cohomology of an end sum of two manifolds. We include a complete proof of Freudenthal’s fundamental theorem on the number of ends of a topological group, and we use our results on dimension-zero end cohomology to prove—without using transfinite induction—a theorem of Nöbeling on freeness of certain modules of continuous functions.
端和端上同调是研究非紧空间的重要不变量。我们提出了端点的拓扑理论的一个独立的阐述,并证明了新的扩展,包括一个固有映射的耗尽的存在。我们将约端上同调定义为射线基空间的相对端上同调。我们利用这些结果证明了King的一个定理的一个版本,该定理计算了两个流形的端和的化简端上同调。我们在拓扑群的端点数上完整地证明了Freudenthal的基本定理,并利用零维端点上同的结果,在不使用超限归纳法的情况下证明了一个关于连续函数的某些模的自由度的定理Nöbeling。
{"title":"Ends and end cohomology","authors":"William G. Bass,&nbsp;Jack S. Calcut","doi":"10.1016/j.exmath.2025.125692","DOIUrl":"10.1016/j.exmath.2025.125692","url":null,"abstract":"<div><div>Ends and end cohomology are powerful invariants for the study of noncompact spaces. We present a self-contained exposition of the topological theory of ends and prove novel extensions including the existence of an exhaustion of a proper map. We define reduced end cohomology as the relative end cohomology of a ray-based space. We use those results to prove a version of a theorem of King that computes the reduced end cohomology of an end sum of two manifolds. We include a complete proof of Freudenthal’s fundamental theorem on the number of ends of a topological group, and we use our results on dimension-zero end cohomology to prove—without using transfinite induction—a theorem of Nöbeling on freeness of certain modules of continuous functions.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 5","pages":"Article 125692"},"PeriodicalIF":0.8,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143906828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Expository article: “Bounded orthogonal systems and the Λ(p)-set problem” by Jean Bourgain 说明性文章:“有界正交系统和Λ(p)-集问题”,作者:Jean Bourgain
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-04-16 DOI: 10.1016/j.exmath.2025.125691
Hongki Jung , Bartosz Langowski , Alexander Ortiz , Truong Vu
In this paper, we present an exposition of the work by Jean Bourgain, in which he resolved the well known conjecture posed by Rudin regarding the existence of Λ(p)-sets.
在本文中,我们对Jean Bourgain的工作进行了阐述,在该工作中,他解决了Rudin关于Λ(p)-集存在性的著名猜想。
{"title":"Expository article: “Bounded orthogonal systems and the Λ(p)-set problem” by Jean Bourgain","authors":"Hongki Jung ,&nbsp;Bartosz Langowski ,&nbsp;Alexander Ortiz ,&nbsp;Truong Vu","doi":"10.1016/j.exmath.2025.125691","DOIUrl":"10.1016/j.exmath.2025.125691","url":null,"abstract":"<div><div>In this paper, we present an exposition of the work by Jean Bourgain, in which he resolved the well known conjecture posed by Rudin regarding the existence of <span><math><mrow><mi>Λ</mi><mrow><mo>(</mo><mi>p</mi><mo>)</mo></mrow></mrow></math></span>-sets.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 5","pages":"Article 125691"},"PeriodicalIF":0.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A comprehensive approach to multifractal analysis 多重分形分析的综合方法
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-04-11 DOI: 10.1016/j.exmath.2025.125690
Zhiming Li , Bilel Selmi , Haythem Zyoudi
This paper investigates how specific techniques have been broadened to suit more general contexts. Among them, multifractal analysis stands out for its adaptability and depth, presenting a unified framework to approach these generalizations. We examine the relative multifractal formalism within the context of metric spaces in a general way. The primary aim is to introduce a generalized concept of general relative multifractal Hausdorff and packing measures. In particular, we delve into the characteristics of the generalized multifractal Hausdorff and packing measures and analyze their impact on the broader multifractal spectrum functions. The investigation explores the connection between these generalized multifractal measures and the nature of general multifractal dimensions within this framework. Further, we establish an equivalence relation between general relative multifractal Hausdorff and packing measures by utilizing density theorems. Moreover, we study various properties of the generalized relative multifractal Hausdorff measures, packing measures, and pre-measures. Lastly, our work addresses the question of whether a subset in Euclidean space Rd with infinite positive Hausdorff measure can contain a compact set of positive finite general relative Hausdorff measures.
本文研究了特定技术如何被扩展以适应更一般的环境。其中,多重分形分析以其适应性和深度突出,为这些概括提供了一个统一的框架。在度量空间的背景下,我们一般地研究了相对多重分形的形式化。主要目的是介绍一般相对多重分形豪斯多夫和包装测度的广义概念。特别地,我们深入研究了广义多重分形Hausdorff测度和包装测度的特征,并分析了它们对广义多重分形谱函数的影响。调查探讨了这些广义多重分形措施和一般多重分形维在这个框架内的性质之间的联系。进一步利用密度定理,建立了广义相对多重分形豪斯多夫测度与填充测度之间的等价关系。此外,我们还研究了广义相对多重分形的Hausdorff测度、填充测度和预测度的各种性质。最后,我们的工作解决了欧几里得空间Rd中具有无限个正豪斯多夫测度的子集是否可以包含一个正有限个一般相对豪斯多夫测度的紧致集合的问题。
{"title":"A comprehensive approach to multifractal analysis","authors":"Zhiming Li ,&nbsp;Bilel Selmi ,&nbsp;Haythem Zyoudi","doi":"10.1016/j.exmath.2025.125690","DOIUrl":"10.1016/j.exmath.2025.125690","url":null,"abstract":"<div><div>This paper investigates how specific techniques have been broadened to suit more general contexts. Among them, multifractal analysis stands out for its adaptability and depth, presenting a unified framework to approach these generalizations. We examine the relative multifractal formalism within the context of metric spaces in a general way. The primary aim is to introduce a generalized concept of general relative multifractal Hausdorff and packing measures. In particular, we delve into the characteristics of the generalized multifractal Hausdorff and packing measures and analyze their impact on the broader multifractal spectrum functions. The investigation explores the connection between these generalized multifractal measures and the nature of general multifractal dimensions within this framework. Further, we establish an equivalence relation between general relative multifractal Hausdorff and packing measures by utilizing density theorems. Moreover, we study various properties of the generalized relative multifractal Hausdorff measures, packing measures, and pre-measures. Lastly, our work addresses the question of whether a subset in Euclidean space <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> with infinite positive Hausdorff measure can contain a compact set of positive finite general relative Hausdorff measures.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 5","pages":"Article 125690"},"PeriodicalIF":0.8,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On a criterion for algebraic independence applied to continued fractions 应用于连分式的代数无关性判据
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-04-10 DOI: 10.1016/j.exmath.2025.125689
Gessica Alecci , Carsten Elsner
From around 2010 onward, Elsner et al.  developed and applied a method in which the algebraic independence of n quantities x1,,xn over a field is transferred to further n quantities y1,,yn by means of a system of polynomials in 2n variables X1,,Xn,Y1,,Yn. In this paper, we systematically study and explain this criterion and its variants. Moreover, we present new results concerning its application to periodic non-regular continued fractions, namely continued fractions with real numbers as partial quotients. We show that given a continued fraction of this type, this criterion can be applied to prove that not only are the convergents algebraically independent from each other, but they are also algebraically independent from the continued fraction.
从2010年左右开始,Elsner等人开发并应用了一种方法,通过2n个变量x1,…,xn, y1,…,yn的多项式系统,将一个域上n个量x1,…,xn的代数独立性转移到另外n个量y1,…,yn上。在本文中,我们系统地研究和解释了这一准则及其变体。此外,我们还对周期非正则连分数,即以实数为部分商的连分数的应用给出了新的结果。我们证明了给定一个这种类型的连分式,这个判据可以用来证明收敛性不仅在代数上相互独立,而且在代数上也与连分式无关。
{"title":"On a criterion for algebraic independence applied to continued fractions","authors":"Gessica Alecci ,&nbsp;Carsten Elsner","doi":"10.1016/j.exmath.2025.125689","DOIUrl":"10.1016/j.exmath.2025.125689","url":null,"abstract":"<div><div>From around 2010 onward, Elsner et al.<!--> <!--> <!-->developed and applied a method in which the algebraic independence of <span><math><mi>n</mi></math></span> quantities <span><math><mrow><msub><mrow><mi>x</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>x</mi></mrow><mrow><mi>n</mi></mrow></msub></mrow></math></span> over a field is transferred to further <span><math><mi>n</mi></math></span> quantities <span><math><mrow><msub><mrow><mi>y</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>y</mi></mrow><mrow><mi>n</mi></mrow></msub></mrow></math></span> by means of a system of polynomials in <span><math><mrow><mn>2</mn><mi>n</mi></mrow></math></span> variables <span><math><mrow><msub><mrow><mi>X</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>X</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>,</mo><msub><mrow><mi>Y</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>Y</mi></mrow><mrow><mi>n</mi></mrow></msub></mrow></math></span>. In this paper, we systematically study and explain this criterion and its variants. Moreover, we present new results concerning its application to periodic non-regular continued fractions, namely continued fractions with real numbers as partial quotients. We show that given a continued fraction of this type, this criterion can be applied to prove that not only are the convergents algebraically independent from each other, but they are also algebraically independent from the continued fraction.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 5","pages":"Article 125689"},"PeriodicalIF":0.8,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Monoids, dynamics and Leavitt path algebras 一元群,动力学与Leavitt路径代数
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-04-09 DOI: 10.1016/j.exmath.2025.125684
Gene Abrams , Roozbeh Hazrat
Leavitt path algebras, which are algebras associated to directed graphs, were first introduced about 20 years ago. They have strong connections to such topics as symbolic dynamics, operator algebras, non-commutative geometry, representation theory, and even chip firing. In this article we invite the reader to sneak a peek at these fascinating algebras and their interplay with several seemingly disparate parts of mathematics.
莱维特路径代数是一种与有向图相关的代数,最早是在20年前提出的。它们与符号动力学、算子代数、非交换几何、表示理论甚至芯片发射等主题有很强的联系。在这篇文章中,我们邀请读者偷看一下这些迷人的代数,以及它们与几个看似不相干的数学部分的相互作用。
{"title":"Monoids, dynamics and Leavitt path algebras","authors":"Gene Abrams ,&nbsp;Roozbeh Hazrat","doi":"10.1016/j.exmath.2025.125684","DOIUrl":"10.1016/j.exmath.2025.125684","url":null,"abstract":"<div><div>Leavitt path algebras, which are algebras associated to directed graphs, were first introduced about 20 years ago. They have strong connections to such topics as symbolic dynamics, operator algebras, non-commutative geometry, representation theory, and even chip firing. In this article we invite the reader to sneak a peek at these fascinating algebras and their interplay with several seemingly disparate parts of mathematics.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 5","pages":"Article 125684"},"PeriodicalIF":0.8,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143936950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Jordan homomorphisms on Hilbert C∗-modules Hilbert C * -模上的Jordan同态
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-04-03 DOI: 10.1016/j.exmath.2025.125687
Xiaofei Qi , Huimin Chen , Jinchuan Hou
We generalize the concept of homomorphisms between Hilbert C-modules to the concept of Jordan homomorphisms. Let M be a Hilbert C-module over a C-algebra A and φ:MM be a map. Under the condition that A is commutative and φ is -linear bounded, we show that φ is a Jordan homomorphism if and only if φ is a homomorphism. In addition, we also discuss the relationship between Φ-unitary maps and automorphisms, and give some conditions under which φ is an automorphism if and only if φ is a Φ-unitary map.
我们将Hilbert C * -模间同态的概念推广到Jordan同态的概念。设M是C∗代数a上的Hilbert C *模,且φ:M→M是映射。在A是可交换的且φ是有界的条件下,证明φ是约当同态的当且仅当φ是同态。此外,我们还讨论了Φ-unitary映射与自同构的关系,并给出了φ是自同构当且仅当Φ-unitary映射的一些条件。
{"title":"Jordan homomorphisms on Hilbert C∗-modules","authors":"Xiaofei Qi ,&nbsp;Huimin Chen ,&nbsp;Jinchuan Hou","doi":"10.1016/j.exmath.2025.125687","DOIUrl":"10.1016/j.exmath.2025.125687","url":null,"abstract":"<div><div>We generalize the concept of homomorphisms between Hilbert C<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span>-modules to the concept of Jordan homomorphisms. Let <span><math><mi>M</mi></math></span> be a Hilbert C<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span>-module over a C<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span>-algebra <span><math><mi>A</mi></math></span> and <span><math><mrow><mi>φ</mi><mo>:</mo><mi>M</mi><mo>→</mo><mi>M</mi></mrow></math></span> be a map. Under the condition that <span><math><mi>A</mi></math></span> is commutative and <span><math><mi>φ</mi></math></span> is <span><math><mi>ℂ</mi></math></span>-linear bounded, we show that <span><math><mi>φ</mi></math></span> is a Jordan homomorphism if and only if <span><math><mi>φ</mi></math></span> is a homomorphism. In addition, we also discuss the relationship between <span><math><mi>Φ</mi></math></span>-unitary maps and automorphisms, and give some conditions under which <span><math><mi>φ</mi></math></span> is an automorphism if and only if <span><math><mi>φ</mi></math></span> is a <span><math><mi>Φ</mi></math></span>-unitary map.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 4","pages":"Article 125687"},"PeriodicalIF":0.8,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The redundancy of Gabor type unitary systems on locally compact abelian groups 局部紧阿贝尔群上Gabor型酉系统的冗余性
IF 0.8 4区 数学 Q2 MATHEMATICS Pub Date : 2025-04-03 DOI: 10.1016/j.exmath.2025.125686
Jingsheng Wang, Pengtong Li
In this paper, we extend the redundancy theorem of J. Gabardo and D. Han for Gabor type unitary systems indexed by full-rank lattices in Euclidean spaces to the setting of locally compact abelian (LCA) groups. Let G be an LCA group, let Λ be a uniform lattice in G, let α be an automorphism of G, and let β be an automorphism of Ĝ. We show that the redundancy of a Gabor type unitary system indexed by α(Λ)×β(Λ) equals the reciprocal of the density of this index set. As an application, we give a new proof of the famous time-frequency density theorem in Gabor analysis.
本文将J. Gabardo和D. Han关于欧几里德空间中满秩格索引的Gabor型酉系统的冗余定理推广到局部紧阿贝尔群的集合上。设G是LCA群,设Λ是G中的一致格,设α是G的自同构,设β是Ĝ的自同构。我们证明了由α(Λ)×β(Λ)⊥索引的Gabor型酉系统的冗余等于该指标集密度的倒数。作为应用,给出了著名的时频密度定理在Gabor分析中的一个新的证明。
{"title":"The redundancy of Gabor type unitary systems on locally compact abelian groups","authors":"Jingsheng Wang,&nbsp;Pengtong Li","doi":"10.1016/j.exmath.2025.125686","DOIUrl":"10.1016/j.exmath.2025.125686","url":null,"abstract":"<div><div>In this paper, we extend the redundancy theorem of J. Gabardo and D. Han for Gabor type unitary systems indexed by full-rank lattices in Euclidean spaces to the setting of locally compact abelian (LCA) groups. Let <span><math><mi>G</mi></math></span> be an LCA group, let <span><math><mi>Λ</mi></math></span> be a uniform lattice in <span><math><mi>G</mi></math></span>, let <span><math><mi>α</mi></math></span> be an automorphism of <span><math><mi>G</mi></math></span>, and let <span><math><mi>β</mi></math></span> be an automorphism of <span><math><mover><mrow><mi>G</mi></mrow><mrow><mo>̂</mo></mrow></mover></math></span>. We show that the redundancy of a Gabor type unitary system indexed by <span><math><mrow><mi>α</mi><mrow><mo>(</mo><mi>Λ</mi><mo>)</mo></mrow><mo>×</mo><mi>β</mi><mrow><mo>(</mo><msup><mrow><mi>Λ</mi></mrow><mrow><mo>⊥</mo></mrow></msup><mo>)</mo></mrow></mrow></math></span> equals the reciprocal of the density of this index set. As an application, we give a new proof of the famous time-frequency density theorem in Gabor analysis.</div></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"43 4","pages":"Article 125686"},"PeriodicalIF":0.8,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
期刊
Expositiones Mathematicae
全部 Acc. Chem. Res. ACS Applied Bio Materials ACS Appl. Electron. Mater. ACS Appl. Energy Mater. ACS Appl. Mater. Interfaces ACS Appl. Nano Mater. ACS Appl. Polym. Mater. ACS BIOMATER-SCI ENG ACS Catal. ACS Cent. Sci. ACS Chem. Biol. ACS Chemical Health & Safety ACS Chem. Neurosci. ACS Comb. Sci. ACS Earth Space Chem. ACS Energy Lett. ACS Infect. Dis. ACS Macro Lett. ACS Mater. Lett. ACS Med. Chem. Lett. ACS Nano ACS Omega ACS Photonics ACS Sens. ACS Sustainable Chem. Eng. ACS Synth. Biol. Anal. Chem. BIOCHEMISTRY-US Bioconjugate Chem. BIOMACROMOLECULES Chem. Res. Toxicol. Chem. Rev. Chem. Mater. CRYST GROWTH DES ENERG FUEL Environ. Sci. Technol. Environ. Sci. Technol. Lett. Eur. J. Inorg. Chem. IND ENG CHEM RES Inorg. Chem. J. Agric. Food. Chem. J. Chem. Eng. Data J. Chem. Educ. J. Chem. Inf. Model. J. Chem. Theory Comput. J. Med. Chem. J. Nat. Prod. J PROTEOME RES J. Am. Chem. Soc. LANGMUIR MACROMOLECULES Mol. Pharmaceutics Nano Lett. Org. Lett. ORG PROCESS RES DEV ORGANOMETALLICS J. Org. Chem. J. Phys. Chem. J. Phys. Chem. A J. Phys. Chem. B J. Phys. Chem. C J. Phys. Chem. Lett. Analyst Anal. Methods Biomater. Sci. Catal. Sci. Technol. Chem. Commun. Chem. Soc. Rev. CHEM EDUC RES PRACT CRYSTENGCOMM Dalton Trans. Energy Environ. Sci. ENVIRON SCI-NANO ENVIRON SCI-PROC IMP ENVIRON SCI-WAT RES Faraday Discuss. Food Funct. Green Chem. Inorg. Chem. Front. Integr. Biol. J. Anal. At. Spectrom. J. Mater. Chem. A J. Mater. Chem. B J. Mater. Chem. C Lab Chip Mater. Chem. Front. Mater. Horiz. MEDCHEMCOMM Metallomics Mol. Biosyst. Mol. Syst. Des. Eng. Nanoscale Nanoscale Horiz. Nat. Prod. Rep. New J. Chem. Org. Biomol. Chem. Org. Chem. Front. PHOTOCH PHOTOBIO SCI PCCP Polym. Chem.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
0
微信
客服QQ
Book学术公众号 扫码关注我们
反馈
×
意见反馈
请填写您的意见或建议
请填写您的手机或邮箱
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
现在去查看 取消
×
提示
确定
Book学术官方微信
Book学术文献互助
Book学术文献互助群
群 号:604180095
Book学术
文献互助 智能选刊 最新文献 互助须知 联系我们:info@booksci.cn
Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。
Copyright © 2023 Book学术 All rights reserved.
ghs 京公网安备 11010802042870号 京ICP备2023020795号-1