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In this work we study a new equivalence relation between w* closed algebras of operators on Hilbert spaces. The algebras A and B are called TRO equivalent if there exists a ternary ring of operators M (i.e. MM*M\subset M) such that A is the…

Operator Algebras · Mathematics 2016-04-19 G. K. Eleftherakis

We introduce and examine the notions of strong $\Delta$-equivalence and strong TRO equivalence for operator spaces. We show that they behave in an analogous way to how strong Morita equivalence does for the category of C*-algebras. In…

Operator Algebras · Mathematics 2018-08-17 George K. Eleftherakis , Evgenios T. A. Kakariadis

We prove that two unital dual operator algebras A, B are stably isomorphic if and only if they are Delta-equivalent, if and only if they have completely isometric normal representations a, b on Hilbert spaces H, K respectively and there…

Operator Algebras · Mathematics 2007-10-01 G. K Eleftherakis , V. I. Paulsen

We prove that two dual operator spaces $X$ and $Y$ are stably isomorphic if and only if there exist completely isometric normal representations $\phi$ and $\psi$ of $X$ and $Y$, respectively, and ternary rings of operators $M_1, M_2$ such…

Operator Algebras · Mathematics 2008-12-16 G. K. Eleftherakis , V. I. Paulsen , I. G. Todorov

We define $\Delta$-equivalence for dual operator systems and prove that it is an equivalence relation. We show that weak TRO-equivalence of dual operator spaces induces a stable isomorphism between them which is given by multiplication with…

Operator Algebras · Mathematics 2025-12-04 Nikolaos Koutsonikos-Kouloumpis

We discuss the two closely related, but different concepts of weak and almost weak stability for the powers of a contraction on a separable Hilbert space. Extending Halmos' and Rohlin's theorems in ergodic theory as a model, we show that…

Functional Analysis · Mathematics 2008-07-21 Tanja Eisner , Andras Sereny

An $n$-tuple of operators $(V_1,...,V_n)$ acting on a Hilbert space $H$ is said to be isometric if the row operator $(V_1,...,V_n) : H^n \to H$ is an isometry. We prove that every isometric $n$-tuple is hyperreflexive, in the sense of…

Operator Algebras · Mathematics 2015-09-15 Adam H. Fuller , Matthew Kennedy

We study the asymptotic behaviour of contractive operators and strongly continuous semigroups on separable Hilbert spaces using the notion of rigidity. In particular, we show that a "typical" contraction $T$ contains the unit circle times…

Functional Analysis · Mathematics 2014-05-01 Tanja Eisner

We introduce a Morita type equivalence: two operator algebras $A$ and $B$ are called strongly $\Delta $-equivalent if they have completely isometric representations $\alpha $ and $\beta $ respectively and there exists a ternary ring of…

Operator Algebras · Mathematics 2016-04-19 G. K. Eleftherakis

We characterize weak* closed unital vector spaces of operators on a Hilbert space $H$. More precisely, we first show that an operator system, which is the dual of an operator space, can be represented completely isometrically and weak*…

Operator Algebras · Mathematics 2014-02-26 David P. Blecher , Bojan Magajna

We show that (for the weak operator topology) the set of unitary operators on a separable infinite-dimensional Hilbert space is residual in the set of all contractions. The analogous result holds for isometries and the strong operator…

Functional Analysis · Mathematics 2014-12-02 Tanja Eisner

We prove that the vast majority of JC*-triples satisfy the condition of universal reversibility. Our characterisation is that a JC*-triple is universally reversible if and only if it has no triple homomorphisms onto Hilbert spaces of…

Operator Algebras · Mathematics 2014-02-26 Leslie J. Bunce , Richard M. Timoney

A complete characterization of Hilbert space operators that generate weakly amenable algebras remains open, even in the case of compact operator. Farenick, Forrest and Marcoux proposed the question that if $T$ is a compact weakly amenable…

Functional Analysis · Mathematics 2010-09-01 Luo Yi Shi , YU Jing Wu , You Qing Ji

We consider C*-algebras associated with stable and unstable equivalence in hyperbolic dynamical systems known as Smale spaces. These systems include shifts of finite type, in which case these C*-algebras are both AF-algebras. These algebras…

Dynamical Systems · Mathematics 2012-08-27 D. Brady Killough , Ian F. Putnam

This paper considers weak supercyclicity for bounded linear operators on a normed space. On the one hand, weak supercyclicity is investigated for classes of Hilbert-space operators: (i) self-adjoint operators are not weakly supercyclic,…

Functional Analysis · Mathematics 2021-01-29 C. S. Kubrusly , B. P. Duggal

The purpose of this paper is to characterize weak supercyclicity for Hilbert-space contractions, which is shown to be equivalent to characterizing weak supercyclicity for unitary operators$.$ This is naturally motivated by an open question…

Functional Analysis · Mathematics 2020-10-27 C. S. Kubrusly , P. C. M. Vieira

We show that for a linear space of operators ${\mathcal M}\subseteq {\mathcal B}(H_1,H_2)$ the following assertions are equivalent. (i) ${\mathcal M} $ is reflexive in the sense of Loginov--Shulman. (ii) There exists an order-preserving map…

Operator Algebras · Mathematics 2015-11-26 Janko Bračič , Lina Oliveira

Four possible definitions of the commutation relation $[S,T]=\Id$ of two closable unbounded operators $S,T$ are compared. The {\em weak} sense of this commutator is given in terms of the inner product of the Hilbert space $\H$ where the…

Mathematical Physics · Physics 2015-06-03 Fabio Bagarello , Atsushi Inoue , Camillo Trapani

We study operator algebraic and function theoretic aspects of algebras of bounded nc functions on subvarieties of the nc domain determined by all levels of the unit ball of an operator space (nc operator balls). Our main result is the…

Operator Algebras · Mathematics 2025-04-15 Jeet Sampat , Orr Shalit

In this paper we characterize $m$-isometric and quasi-$m$-isometric weighted conditional type (WCT) operators on the Hilbert space $L^2(\mu)$. Also, we prove that the subclasses of $m$-isometric and quasi-$m$-isometric of normal WCT…

Functional Analysis · Mathematics 2025-09-30 Y. Estaremi , M. S. Al Ghafri , S. Shamsigamchi
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