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A notion of super operator system is defined which generalizes the usual notion of operator systems to include certain unital involutive operator spaces which cannot be represented completely isometric as a concrete operator system on some…

Operator Algebras · Mathematics 2013-08-05 Ulrich Haag

It has been a longstanding problem whether every amenable operator algebra is isomorphic to a (necessarily nuclear) C*-algebra. In this note, we give a nonseparable counterexample. The existence of a separable counterexample remains an open…

Operator Algebras · Mathematics 2014-03-17 Yemon Choi , Ilijas Farah , Narutaka Ozawa

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 $\mathcal{A}$ be a separable nuclear C*-algebra, and let $\mathcal{M}$ be a semifinite von Neumann factor with separable predual. Let $\phi, \psi: \mathcal{A} \rightarrow \mathcal{M}$ be essential trivial extensions with $\phi(a) -…

Operator Algebras · Mathematics 2025-12-09 Ping Wong Ng , Cangyuan Wang

Let $A$ be a separable, unital and exact $C^*$-algebra satisfying the universal coefficient theorem. We prove uniqueness theorems up to unitary conjugacy for unital, full and nuclear maps from $A$ into ultraproducts of finite von Neumann…

Operator Algebras · Mathematics 2026-05-15 Shanshan Hua , Stuart White

We study the notions of nuclearity and exactness for module maps on $C^{*}$-algebras which are $C^*$-module over another $C^*$-algebra with compatible actions and examine finite approximation properties of such $C^*$-modules. We prove…

Operator Algebras · Mathematics 2022-06-15 Massoud Amini

The $C^{\ast}$-algebra $\mathcal{U}_{nc}(n)$ is the universal $C^{\ast}$-algebra generated by $n^2$ generators $u_{ij}$ that make up a unitary matrix. We prove that Kirchberg's formulation of Connes' embedding problem has a positive answer…

Operator Algebras · Mathematics 2018-01-11 Samuel J. Harris

In this paper, we show that a completely positive linear map is weakly nuclear if and only if its complexification is weakly nuclear. It is shown that a real $C^*$-algebra is exact if and only if its complexification is exact and similar…

Operator Algebras · Mathematics 2020-05-19 Ali Ebadian , Ali Jabbari

We prove that the isomorphism problem for separable nuclear C*-algebras is complete in the class of orbit equivalence relations. In fact, already the isomorphism of simple, separable AI C*-algebras is a complete orbit equivalence relation.…

Operator Algebras · Mathematics 2013-07-16 Marcin Sabok

We give a classification theorem for unital separable nuclear simple \CA s with tracial rank no more than one. Let $A$ and $B$ be two unital separable simple nuclear \CA s with $TR(A), TR(B)\le 1$ which satisfy the universal coefficient…

Operator Algebras · Mathematics 2007-05-23 Huaxin Lin

We continue our study of operator algebras with and contractive approximate identities (cais). In earlier papers we have introduced and studied a new notion of positivity in operator algebras, with an eye to extending certain C*-algebraic…

Operator Algebras · Mathematics 2014-07-08 David P. Blecher , Charles John Read

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

This work is motivated by Radulescu's result on the comparison of C*-tensor norms on C*(F_n) x C*(F_n). For unital C*-algebras A and B, there are natural inclusions of A and B into their unital free product, their maximal tensor product and…

Operator Algebras · Mathematics 2014-10-09 Tobias Fritz

We examine k-minimal and k-maximal operator spaces and operator systems, and investigate their relationships with the separability problem in quantum information theory. We show that the matrix norms that define the k-minimal operator…

Operator Algebras · Mathematics 2011-02-08 Nathaniel Johnston , David W. Kribs , Vern I. Paulsen , Rajesh Pereira

The "Up-and-down" theorem which describes the structure of the Boolean algebra of fragments of a linear positive operator is the well known result of the operator theory. We prove an analog of this theorem for a positive abstract Uryson…

Functional Analysis · Mathematics 2015-07-29 Marat A. Pliev

Let $X$ be a right Hilbert module over a $C^*$-algebra $A$ equipped with the canonical operator space structure. We define an elementary operator on $X$ as a map $\phi : X \to X$ for which there exists a finite number of elements $u_i$ in…

Operator Algebras · Mathematics 2020-01-13 Ljiljana Arambašić , Ilja Gogić

We study the issue of issue of purity (as a completely positive linear map) for identity maps on operators systems and for their completely isometric embeddings into their C$^*$-envelopes and injective envelopes. Our most general result…

Operator Algebras · Mathematics 2020-06-16 Douglas Farenick , Ryan Tessier

In this paper we study the operator inequality \phi(X)\leq X and the operator equation \phi(X)= X, where \phi is a w^*-continuous positive (resp. completely positive) linear map on B(H). We show that their solutions are in one-to-one…

Operator Algebras · Mathematics 2007-05-23 Gelu Popescu

Our main result is a theorem saying that a bounded operator $A$ on a Hilbert space belongs to a certain set associated with its self-commutator $[A^*,A]$, provided that $A-zI$ can be approximated by invertible operators for all complex…

Operator Algebras · Mathematics 2009-10-25 N. Filonov , Y. Safarov

Let $\mathcal E$ denote the set of all unital entanglement breaking (UEB) linear maps defined on an operator system $\mathcal S \subset M_d$ and, mapping into $M_n$. As it turns out, the set $\mathcal E$ is not only convex in the classical…

Operator Algebras · Mathematics 2024-01-12 Sriram Balasubramanian , Neha Hotwani