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Given a C$^*$-correspondence $X$, we give necessary and sufficient conditions for the tensor algebra $\mathcal T_X^+$ to be hyperrigid. In the case where $X$ is coming from a topological graph we obtain a complete characterization.

Operator Algebras · Mathematics 2019-11-27 Elias Katsoulis , Christopher Ramsey

We establish logical equivalence between statements involving * the Cuntz C*-algebra $\mathcal O_\infty$ with its canonical diagonal; * graph C*-algebras with their canonical diagonals; * Leavitt path algebras over general fields with their…

Operator Algebras · Mathematics 2025-11-12 Søren Eilers , Efren Ruiz

When a locally compact group acts on a C*-correspondence, it also acts on the associated Cuntz-Pimsner algebra in a natural way. Hao and Ng have shown that when the group is amenable the Cuntz-Pimsner algebra of the crossed product…

Operator Algebras · Mathematics 2015-01-21 Erik Bédos , S. Kaliszewski , John Quigg , David Robertson

Two graphs are co-spectral if their respective adjacency matrices have the same multi-set of eigenvalues. A graph is said to be determined by its spectrum if all graphs that are co-spectral with it are isomorphic to it. We consider these…

Logic in Computer Science · Computer Science 2016-09-15 Anuj Dawar , Simone Severini , Octavio Zapata

In this paper we describe all surjective isometries between open subgroups of the groups of invertible elements in unital $C^{*}$-algebras.

Operator Algebras · Mathematics 2011-05-20 Osamu Hatori , Keiichi Watanabe

We determine the primitive ideal space and hence the ideal lattice of a large class of separable groupoid C*-algebras that includes all 2-graph C*-algebras. A key ingredient is the notion of harmonious families of bisections in etale…

Operator Algebras · Mathematics 2023-12-19 Kevin Aguyar Brix , Toke Meier Carlsen , Aidan Sims

We prove that the automorphisms of any separable C*-algebra that does not have continuous trace are not classifiable by countable structures up to unitary equivalence. This implies a dichotomy for the Borel complexity of the relation of…

Operator Algebras · Mathematics 2016-05-06 Martino Lupini

It is a well-known fact that endomorphisms of $B(H)$ are intimately connected with families of mutually orthogonal isometries, i.e. with representations of the so-called Toeplitz $C^*$-algebras. In this paper we consider a natural…

Operator Algebras · Mathematics 2019-05-08 Philip M. Gipson

For a closed subgroup of a locally compact group the Rieffel induction process gives rise to a $C^*$-correspondence over the $C^*$-algebra of the subgroup. We study the associated Cuntz-Pimsner algebra and show that, by varying the subgroup…

Operator Algebras · Mathematics 2018-01-22 S. Kaliszewski , Nadia S. Larsen , John Quigg

We find a substantial class of pairs of $*$-homomorphisms between graph C*-algebras of the form $C^*(E)\hookrightarrow C^*(G)\twoheadleftarrow C^*(F)$ whose pullback C*-algebra is an AF graph C*-algebra. Our result can be interpreted as a…

Quantum Algebra · Mathematics 2020-11-25 Alexandru Chirvasitu , Piotr M. Hajac , Mariusz Tobolski

We define a categorical framework in which we build a systematic construction that provides generic invariants for C*-algebras. The benefit is significant as we show that any invariant arising this way automatically enjoys nice properties…

Operator Algebras · Mathematics 2023-09-06 Laurent Cantier

We consider two Z/2Z-actions on the Podles generic quantum spheres. They yield, as noncommutative quotient spaces, the Klimek-Lesniewski q-disc and the quantum real projective space, respectively. The C*-algebras of all these quantum spaces…

Quantum Algebra · Mathematics 2009-11-07 P. M. Hajac , R. Matthes , W. Szymanski

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 classify unital monomorphisms into certain simple Z-stable C^*-algebras up to approximate unitary equivalence. The domain algebra C is allowed to be any unital separable commutative C^*-algebra, or any unital simple separable nuclear…

Operator Algebras · Mathematics 2010-11-04 Hiroki Matui

Given a countable abelian group $A$, we construct a row finite directed graph $\Gamma(A)$ such that the $K_{0}$-group of the graph $\textrm{C}^{\ast}$-algebra $\textrm{C}^{\ast}(\Gamma(A))$ is canonically isomorphic to $A$. Moreover, each…

Operator Algebras · Mathematics 2025-12-23 Swarnendu Datta , Debashish Goswami , Soumalya Joardar

It is shown that a separable C*-algebra is inner quasidiagonal if and only if it has a separating family of quasidiagonal irreducible representations. As a consequence, a separable C*-algebra is a strong NF algebra if and only if it is…

Operator Algebras · Mathematics 2007-12-12 Bruce Blackadar , Eberhard Kirchberg

We address the classification problem for graph $C^*$-algebras of finite graphs (finitely many edges and vertices), containing the class of Cuntz-Krieger algebras as a prominent special case. Contrasting earlier work, we do not assume that…

Operator Algebras · Mathematics 2018-03-05 Søren Eilers , Gunnar Restorff , Efren Ruiz , Adam P. W. Sørensen

The graph groupoids of directed graphs are topologically isomorphic if and only if there is a diagonal-preserving ring *-isomorphism between the Leavitt path algebras.

Rings and Algebras · Mathematics 2016-04-05 Jonathan H. Brown , Lisa Orloff Clark , Astrid an Huef

We will show that for a separable exact $C^*$-algebra with a faithful amenable trace, the property that all amenable traces are quasidiagonal is invariant under homotopy.

Operator Algebras · Mathematics 2024-12-30 Robert Neagu

We prove that the graph C*-algebra $C^*(E)$ of a trimmable graph $E$ is $U(1)$-equivariantly isomorphic to a pullback C*-algebra of a subgraph C*-algebra $C^*(E'')$ and the C*-algebra of functions on a circle tensored with another subgraph…

K-Theory and Homology · Mathematics 2018-09-10 Francesca Arici , Francesco D'Andrea , Piotr M. Hajac , Mariusz Tobolski
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