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We introduce the notion of continuous orbit equivalence for partial dynamical systems, and give an equivalent characterization in terms of Cartan-isomorphisms for partial C*-crossed products. Both graph C*-algebras and semigroup C*-algebras…

Operator Algebras · Mathematics 2016-03-31 Xin Li

We characterise when the Leavitt path algebras over $\mathbb{Z}$ of two arbitrary countable directed graphs are $*$-isomorphic by showing that two Leavitt path algebras over $\mathbb{Z}$ are $*$-isomorphic if and only if the corresponding…

Rings and Algebras · Mathematics 2018-04-12 Toke Meier Carlsen

Given a simple undirected graph, one can construct from it a $c$-step nilpotent Lie algebra for every $c \geq 2$ and over any field $K$, in particular also over the real and complex numbers. These Lie algebras form an important class of…

Dynamical Systems · Mathematics 2022-09-15 Jonas Deré , Thomas Witdouck

We note that the deep results of Grunewald and Segal on algorithmic problems for arithmetic groups imply the decidability of several matrix equivalence problems involving poset-blocked matrices over Z. Consequently, results of Eilers,…

Operator Algebras · Mathematics 2020-06-02 Mike Boyle , Benjamin Steinberg

In this paper we define a pair of faithful functors that map isomorphic and isotopic finite-dimensional algebras over finite fields to isomorphic graphs. These functors reduce the cost of computation that is usually required to determine…

Rings and Algebras · Mathematics 2017-02-08 O. J. Falcón , R. M. Falcón , J. Núñez , A. M. Pacheco , M. T. Villar

To an arbitrary directed graph we associate a row-finite directed graph whose C*-algebra contains the C*-algebra of the original graph as a full corner. This allows us to generalize results for C*-algebras of row-finite graphs to…

Operator Algebras · Mathematics 2007-05-23 D. Drinen , M. Tomforde

We define a solvable extension of the graph 2-step nilpotent Lie algebras of [5] by adding elements corresponding to the 3-cliques of the graph. We study some of their basic properties and we prove that two such Lie algebras are isomorphic…

Rings and Algebras · Mathematics 2017-09-21 Gueo Grantcharov , Vladimir Grantcharov , Plamen Iliev

We prove the following two results. First, the isometry semigroup of a unital properly infinite nuclear C*-algebra is right amenable. Second, the unitary group of a unital simple monotracial C*-algebra whose tracial GNS representation is…

Operator Algebras · Mathematics 2023-09-01 Narutaka Ozawa

We provide the rigorous foundations for a categorical approach to the classification of C*-dynamics up to cocycle conjugacy. Given a locally compact group $G$, we consider a category of (twisted) $G$-C*-algebras, where morphisms between two…

Operator Algebras · Mathematics 2022-02-22 Gabor Szabo

We study graph $C^*$-algebras equipped with generalised gauge actions, and characterise in terms of groupoids and groupoid cocycles when two graph $C^*$-algebras are isomorphic by a diagonal-preserving isomorphism that intertwines the…

Operator Algebras · Mathematics 2018-10-08 Toke Meier Carlsen , James Rout

Let X be a path connected, compact metric space and let A be a unital separable simple nuclear Z-stable real rank zero C*-algebra. We classify all the unital *-embeddings (up to approximate unitary equivalence) of C(X) into A. Specifically,…

Operator Algebras · Mathematics 2007-09-11 P. W. Ng , Wilhelm Winter

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

We introduce a divisibility-type condition for directed graphs that is necessary for $\mathcal{Z}$-stability of the corresponding graph $C^*$-algebra. We prove that this condition is sufficient if either the graph $E$ has no cycles or the…

Operator Algebras · Mathematics 2025-11-05 Gregory Faurot

We study stable finiteness of extensions of 2-graph C*-algebras determined by saturated hereditary sets of vertices. We use two iterations of the Pimsner-Voiculescu sequence to calculate the map in K-theory induced by the inclusion of a…

Operator Algebras · Mathematics 2021-12-01 Astrid an Huef , Abraham C. S. Ng , Aidan Sims

We prove that the C*-algebra of a second-countable, \'etale, amenable groupoid is simple if and only if the groupoid is topologically principal and minimal. We also show that if G has totally disconnected unit space, then the associated…

Operator Algebras · Mathematics 2013-10-10 Jonathan H. Brown , Lisa Orloff Clark , Cynthia Farthing , Aidan Sims

We consider the boundary-path groupoids of topological higher-rank graphs. We show that the all such groupoids are topologically amenable. We deduce that the C*-algebras of topological higher-rank graphs are nuclear and prove versions of…

Operator Algebras · Mathematics 2012-09-11 Jean N. Renault , Aidan Sims , Dana P. Williams , Trent Yeend

I show how to associate a Clifford algebra to a graph. I describe the structure of these Clifford graph algebras and provide many examples and pictures. I describe which graphs correspond to isomorphic Clifford algebras and also discuss…

Combinatorics · Mathematics 2013-06-25 Tanya Khovanova

Given a compact space X and two commuting continuous open surjective maps sigma_1, sigma_2 : X --> X, we construct certain C*-algebras that reflect the dynamics of the N^2-action. When the maps sigma_1, sigma_2 are local homeomorphisms,…

Operator Algebras · Mathematics 2007-05-23 Valentin Deaconu

We define $G$-cospectrality of two $G$-gain graphs $(\Gamma,\psi)$ and $(\Gamma',\psi')$, proving that it is a switching isomorphism invariant. When $G$ is a finite group, we prove that $G$-cospectrality is equivalent to cospectrality with…

Combinatorics · Mathematics 2022-06-13 Matteo Cavaleri , Alfredo Donno

In this note we state a conjecture that characterizes unital C*-algebras for which the unitary group is amenable as a topological group in the norm topology. We prove the conjecture for simple, separable, stably finite, unital, $\mathcal…

Operator Algebras · Mathematics 2024-12-03 Vadim Alekseev , Max Schmidt , Andreas Thom