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We give a complete description of order isomorphisms between operator intervals in general von Neumann algebras. For the description, we use Jordan $^*$-isomorphisms and locally measurable operators. Our results generalize several works by…

Operator Algebras · Mathematics 2019-03-12 Michiya Mori

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

Let $\mathcal{H}$ be a complex, separable Hilbert space and $\mathcal{B}(\mathcal{H})$ denote the algebra of all bounded linear operators acting on $\mathcal{H}$. Given a unitarily-invariant norm $\| \cdot \|_u$ on…

Functional Analysis · Mathematics 2019-08-22 Laurent W. Marcoux , Yuanhang Zhang

In this paper, we study $L^1$-matrix convex sets $\{K_{n}\}$ in $*$-locally convex spaces and show that every C$^*$-ordered operator space is complete isometrically, completely isomorphic to $\{A_{0}(K_{n}, M_{n}(V))\}$ for a suitable…

Operator Algebras · Mathematics 2018-02-13 Anindya Ghatak , Anil Kumar Karn

This is a companion to recent papers of the authors; here we construct the `noncommutative Shilov boundary' of a (possibly nonunital) selfadjoint ordered space of Hilbert space operators. The morphisms in the universal property of the…

Operator Algebras · Mathematics 2007-05-23 David P. Blecher , Kay Kirkpatrick , Matthew Neal , Wend Werner

We prove the Weyl-von Neumann-Berg theorem for quaternionic right linear operators (not necessarily bounded) in a quaternionic Hilbert space: Let $N$ be a right linear normal (need not be bounded) operator in a quaternionic separable…

Spectral Theory · Mathematics 2016-09-01 G. Ramesh

It is proven that the absolutely continuous spectrum of matrix Schr\"{o}dinger operators coincides (with the multiplicity taken into account) with the spectrum of the unperturbed operator if the (matrix) potential is square integrable. The…

Mathematical Physics · Physics 2016-04-04 Stanislav A. Molchanov , Boris R. Vainberg

An operator system $\cl S$ with unit $e$, can be viewed as an Archimedean order unit space $(\cl S,\cl S^+,e)$. Using this Archimedean order unit space, for a fixed $k\in \bb N$ we construct a super k-minimal operator system OMIN$_k(\cl S)$…

Operator Algebras · Mathematics 2011-11-15 Blerina Xhabli

A vector subspace $\cls$ of $\IM_n(\IC)$ is called unital operator system if $x \in \cls$ if and only if $x^* \in \cls$ and the identity operator $I_n \in \cls$, where $n$ is any fixed positive integer. Let $C^*(\cls)$ be the $C^*$…

Functional Analysis · Mathematics 2023-08-03 Anilesh Mohari

A necessary and sufficient condition for an operator space to support a multiplication making it completely isometric and isomorphic to a unital operator algebra is proved. The condition involves only the holomorphic structure of the Banach…

Operator Algebras · Mathematics 2015-12-11 Matthew Neal , Bernard Russo

We obtain several essential self-adjointness conditions for a Schroedinger type operator D*D+V acting in sections of a vector bundle over a manifold M. Here V is a locally square-integrable bundle map. Our conditions are expressed in terms…

Spectral Theory · Mathematics 2015-06-26 Maxim Braverman , Ognjen Milatovic , Mikhail Shubin

Generalizing Pisier's idea, we introduce a Hilbertian matrix cross normed space associated with a pair of symmetric normed ideals. When the two ideals coincide, we show that our construction gives an operator space if and only if the ideal…

Operator Algebras · Mathematics 2007-05-23 Takahiro Ohta

We define $\Delta$-equivalence for operator systems and show that it is identical to stable isomorphism. We define $\Delta$-contexts and bihomomorphism contexts and show that two operator systems are $\Delta$-equivalent if and only if they…

Operator Algebras · Mathematics 2026-02-27 George K. Eleftherakis , Evgenios T. A. Kakariadis , Ivan G. Todorov

The set of normalizers between von Neumann (or, more generally, reflexive) algebras A and B, (that is, the set of all operators x such that xAx* is a subset of B and x*Bx is a subset of A) possesses `local linear structure': it is a union…

Operator Algebras · Mathematics 2022-06-29 A. Katavolos , I. G. Todorov

Operator matrices have played a significant role in studying Hilbert space operators. In this paper, we discuss further properties of operator matrices and present new estimates for the operator norms and numerical radii of such operators.…

Functional Analysis · Mathematics 2022-06-28 Fuad Kittaneh , Hamid Reza Moradi , Mohammad Sababheh

We establish new integral inequalities for the numerical radius and the operator norm of bounded linear operators on Hilbert spaces. Our results refine classical triangle-type and operator matrix inequalities by incorporating convex…

Functional Analysis · Mathematics 2026-02-17 Shiva Sheybani , Hamid Reza Moradi , Mohammad Sababheh

New examples of matrix quasi exactly solvable Schroedinger operators are constructed. One of them constitutes a matrix generalization of the quasi exactly solvable anharmonic oscillator, the corresponding invariant vector space is…

Quantum Physics · Physics 2009-11-07 Yves Brihaye , Betti Hartmann

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

Let $A$ be a unital C*-algebra, $S$ be an operator $A$-system and $E$ be an operator space that is a left operator $A$-module. We introduce the symmetrisation of the pair $(E,S)$ as the Hausdorff completion of the balanced tensor product…

Operator Algebras · Mathematics 2025-03-20 George K. Eleftherakis , Evgenios T. A. Kakariadis , Ivan G. Todorov

Let $S$ be a complete operator system with a generating cone; i.e. $S_\sa = S_+ - S_+$. We show that there is a matrix norm on the dual space $S^*$, under which, and the usual dual matrix cone, $S^*$ becomes a dual operator system with a…

Operator Algebras · Mathematics 2025-04-09 Yu-Shu Jia , Chi-Keung Ng