We prove a real version of the Lax-Phillips Theorem and classify outgoing reflection positive orthogonal one-parameter groups. Using these results, we provide a normal form for outgoing monotone geodesics in the set Stand(H) of standard subspaces on some complex Hilbert space H. As the modular operators of a standard subspace are closely related to positive Hankel operators, our results are obtained by constructing some explicit symbols for positive Hankel operators. We also describe which of the monotone geodesics in Stand(H) arise from the unitary one-parameter groups described in Borchers' Theorem and provide explicit examples of monotone geodesics that are not of this type.
我们证明了拉克斯-菲利普斯定理的真实版本,并对出射反射正交单参数群进行了分类。利用这些结果,我们为某个复希尔伯特空间 H 上的标准子空间集合 Stand(H) 中的出射单调大地线提供了一个正则表达式。由于标准子空间的模算子与正汉克尔算子密切相关,我们的结果是通过构造正汉克尔算子的一些显式符号得到的。我们还描述了Stand(H)中哪些单调大地线是由Borchers定理中描述的单元单参数群产生的,并提供了不属于这种类型的单调大地线的明确例子。
{"title":"Outgoing monotone geodesics of standard subspaces","authors":"Jonas Schober","doi":"arxiv-2409.08184","DOIUrl":"https://doi.org/arxiv-2409.08184","url":null,"abstract":"We prove a real version of the Lax-Phillips Theorem and classify outgoing\u0000reflection positive orthogonal one-parameter groups. Using these results, we\u0000provide a normal form for outgoing monotone geodesics in the set Stand(H) of\u0000standard subspaces on some complex Hilbert space H. As the modular operators of\u0000a standard subspace are closely related to positive Hankel operators, our\u0000results are obtained by constructing some explicit symbols for positive Hankel\u0000operators. We also describe which of the monotone geodesics in Stand(H) arise\u0000from the unitary one-parameter groups described in Borchers' Theorem and\u0000provide explicit examples of monotone geodesics that are not of this type.","PeriodicalId":501036,"journal":{"name":"arXiv - MATH - Functional Analysis","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The aim of this article is to introduce the H-infinity functional calculus for unbounded bisectorial operators in a Clifford module over the algebra R_n. While recent studies have focused on bounded operators or unbounded paravector operators, we now investigate unbounded fully Clifford operators and define polynomially growing functions of them. We first generate the omega-functional calculus for functions that exhibit an appropriate decay at zero and at infinity. We then extend to functions with a finite value at zero and at infinity. Finally, using a subsequent regularization procedure, we can define the H-infinity functional calculus for the class of regularizable functions, which in particular include functions with polynomial growth at infinity and, if T is injective, also functions with polynomial growth at zero.
本文旨在介绍代数 R_n 上克利福德模中无界二叉算子的 H-infinity 函数微积分。最近的研究主要集中于有界算子或无界旁向量算子,而我们现在研究的是无界全克利福德算子,并定义它们的波函数。我们首先为在零点和无限点表现出适当衰减的函数生成欧米伽函数微积分。然后,我们将其扩展到在零点和无限点具有有限值的函数。最后,利用随后的正则化过程,我们可以为一类可正则化函数定义 H-infinity 函数微积分,这一类函数尤其包括在无穷处具有多项式增长的函数,如果 T 是注入式的,还包括在零处具有多项式增长的函数。
{"title":"The $H^infty$-functional calculus for bisectorial Clifford operators","authors":"Francesco Mantovani, Peter Schlosser","doi":"arxiv-2409.07249","DOIUrl":"https://doi.org/arxiv-2409.07249","url":null,"abstract":"The aim of this article is to introduce the H-infinity functional calculus\u0000for unbounded bisectorial operators in a Clifford module over the algebra R_n.\u0000While recent studies have focused on bounded operators or unbounded paravector\u0000operators, we now investigate unbounded fully Clifford operators and define\u0000polynomially growing functions of them. We first generate the omega-functional\u0000calculus for functions that exhibit an appropriate decay at zero and at\u0000infinity. We then extend to functions with a finite value at zero and at\u0000infinity. Finally, using a subsequent regularization procedure, we can define\u0000the H-infinity functional calculus for the class of regularizable functions,\u0000which in particular include functions with polynomial growth at infinity and,\u0000if T is injective, also functions with polynomial growth at zero.","PeriodicalId":501036,"journal":{"name":"arXiv - MATH - Functional Analysis","volume":"60 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we proved that $T_{z^n}$ acting on the $mathbb{C}^m$-valued Hardy space $H_{mathbb{C}^m}^2(mathbb{D})$, is unitarily equivalent to $bigoplus_1^{mn}T_z$, where $T_z$ is acting on the scalar-valued Hardy space $H_{mathbb{C}}^2(mathbb{D})$. And using the matrix manipulations combined with operator theory methods, we completely describe the reducing subspaces of $T_{z^n}$ on $H_{mathbb{C}^m}^2(mathbb{D})$.
{"title":"On unitary equivalence and reducing subspaces of analytic Toeplitz operator on vector-valued Hardy space","authors":"Cui Chen, Yucheng Li, Ya Wang","doi":"arxiv-2409.07112","DOIUrl":"https://doi.org/arxiv-2409.07112","url":null,"abstract":"In this paper, we proved that $T_{z^n}$ acting on the $mathbb{C}^m$-valued\u0000Hardy space $H_{mathbb{C}^m}^2(mathbb{D})$, is unitarily equivalent to\u0000$bigoplus_1^{mn}T_z$, where $T_z$ is acting on the scalar-valued Hardy space\u0000$H_{mathbb{C}}^2(mathbb{D})$. And using the matrix manipulations combined\u0000with operator theory methods, we completely describe the reducing subspaces of\u0000$T_{z^n}$ on $H_{mathbb{C}^m}^2(mathbb{D})$.","PeriodicalId":501036,"journal":{"name":"arXiv - MATH - Functional Analysis","volume":"175 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We introduce and study the notion of hereditary frequent hypercyclicity, which is a reinforcement of the well known concept of frequent hypercyclicity. This notion is useful for the study of the dynamical properties of direct sums of operators; in particular, a basic observation is that the direct sum of a hereditarily frequently hypercyclic operator with any frequently hypercyclic operator is frequently hypercyclic. Among other results, we show that operators satisfying the Frequent Hypercyclicity Criterion are hereditarily frequently hypercyclic, as well as a large class of operators whose unimodular eigenvectors are spanning with respect to the Lebesgue measure. On the other hand, we exhibit two frequently hypercyclic weighted shifts $B_w,B_{w'}$ on $c_0(mathbb{Z}_+)$ whose direct sum $B_woplus B_{w'}$ is not $mathcal{U}$-frequently hypercyclic (so that neither of them is hereditarily frequently hypercyclic), and we construct a $C$-type operator on $ell_p(mathbb{Z}_+)$, $1le p