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We introduce a new method of expressing a $k$-graph $C^*$-algebra as a Cuntz-Pimsner algebra. Kumjian, Pask, and Sims have done this directly, using a linking algebra approach and a $(k-1)$-graph algebra. This can be iterated downward. Our…

Operator Algebras · Mathematics 2026-04-22 Valentin Deaconu , Menevşe Eryüzlü Paulovicks , S. Kaliszewski , John Quigg

In this paper, we introduce a C*-algebra associated to any substitution (via its Bratteli diagram model). We show that this C*-algebra contains the partial crossed product C*-algebra of the corresponding Bratteli-Vershik system and show…

Operator Algebras · Mathematics 2011-08-24 Daniel Gonçalves , Danilo Royer

We call an $\mathbb{R}$-algebra locally complexified-gentle if it becomes a locally gentle $\mathbb{C}$-algebra up to Morita equivalence after complexification. We use modulated quivers to introduce two types of locally complexified-gentle…

Representation Theory · Mathematics 2026-01-14 Jie Li , Chao Zhang

A directed graph is semi-transitive if and only if it is acyclic and for any directed path $u_1\rightarrow u_2\rightarrow \cdots \rightarrow u_t$, $t \geq 2$, either there is no edge from $u_1$ to $u_t$ or all edges $u_i\rightarrow u_j$…

Combinatorics · Mathematics 2021-08-13 Kittitat Iamthong , Sergey Kitaev

We construct a functor that maps $C^*$-correspondences to their Cuntz-Pimsner algebras. The objects in our domain category are $C^*$-correspondences, and the morphisms are the isomorphism classes of $C^*$-correspondences satisfying certain…

Operator Algebras · Mathematics 2020-09-29 M. Eryüzlü

We continue our study of the general theory of possibly nonselfadjoint algebras of operators on a Hilbert space, and modules over such algebras, developing a little more technology to connect `nonselfadjoint operator algebra' with the…

Operator Algebras · Mathematics 2007-05-23 David P. Blecher

This dissertation concerns the classification of groupoid and higher-rank graph C*-algebras and has two main components. Firstly, for a groupoid it is shown that the notions of strength of convergence in the orbit space and…

Operator Algebras · Mathematics 2013-05-28 Robert Hazlewood

We give a complete description of which unital graph C*-algebras are semiprojective, and use it to disprove two conjectures by Blackadar. To do so, we perform a detailed analysis of which projections are properly infinite in such…

Operator Algebras · Mathematics 2015-12-24 Søren Eilers , Takeshi Katsura

We characterise simplicity of twisted C*-algebras of row-finite k-graphs with no sources. We show that each 2-cocycle on a cofinal k-graph determines a canonical second-cohomology class for the periodicity group of the graph. The groupoid…

Operator Algebras · Mathematics 2016-06-28 Alex Kumjian , David Pask , Aidan Sims

In this paper we verify that the graph forms a complete invariant for Banach algebra isomorphisms of tensor algebras of graphs. For tensor algebras associated with countable directed graphs having no sinks the graph forms an invariant for…

Operator Algebras · Mathematics 2007-05-23 Elias Katsoulis , David Kribs

We produce a new, shorter construction of a minor-universal planar graph.

Combinatorics · Mathematics 2023-09-14 George Kontogeorgiou

We show that a separable C*-algebra is an inductive limits of projective C*-algebras if and only if it has trivial shape, that is, if it is shape equivalent to the zero C*-algebra. In particular, every contractible C*-algebra is an…

Operator Algebras · Mathematics 2017-12-15 Hannes Thiel

We give a dynamical characterization of categorical Morita equivalence between compact quantum groups. More precisely, by a Tannaka-Krein type duality, a unital C*-algebra endowed with commuting actions of two compact quantum groups…

Operator Algebras · Mathematics 2021-06-09 Sergey Neshveyev , Makoto Yamashita

A partial action is associated with a normal weakly left resolving labelled space such that the crossed product and labelled space $C^*$-algebras are isomorphic. An improved characterization of simplicity for labelled space $C^*$-algebras…

Operator Algebras · Mathematics 2019-09-11 Gilles G. de Castro , Daniel W. van Wyk

Given a $k$-graph $\Lambda$ and an element $p$ of $\NN^k$, we define the dual $k$-graph, $p\Lambda$. We show that when $\Lambda$ is row-finite and has no sources, the $C^*$-algebras $C^*(\Lambda)$ and $C^*(p\Lambda)$ coincide. We use this…

Operator Algebras · Mathematics 2007-05-23 Stephen Allen , David Pask , Aidan Sims

We classify the rational Cherednik algebras H_c(W) (and their spherical subalgebras) up to isomorphism and Morita equivalence in case when W is the symmetric group and `c' is a generic parameter value.

Quantum Algebra · Mathematics 2007-05-23 Yuri Berest , Pavel Etingof , Victor Ginzburg

We calculate the $K$-theory of the reduced $C^*$-algebra $C^*_r(G)$ of a reductive $p$-adic group $G$. To do so, we show that each direct summand in Plymen's Plancherel decomposition of $C^*_r(G)$ is Morita equivalent to a twisted crossed…

Representation Theory · Mathematics 2026-04-13 Pierre Clare , Tyrone Crisp

We introduce a graph theoretic property called Condition (N) for finitely separated graphs and prove that it is equivalent to both nuclearity and exactness of the associated universal tame graph C*-algebra.

Operator Algebras · Mathematics 2017-05-15 Matias Lolk

We show that certain pullbacks of $*$-algebras equivariant with respect to a compact group action remain pullbacks upon completing to $C^*$-algebras. This unifies a number of results in the literature on graph algebras, showing that…

Category Theory · Mathematics 2020-02-07 Alexandru Chirvasitu

For Ore semigroups $P$ with an order unit, we prove that there is a bijection between $E_0$-semigroups over $P$ and product systems of $C^{*}$-correspondences over $P^{op}$. We exploit this bijection and show that the reduced…

Operator Algebras · Mathematics 2025-07-29 Md Amir Hossain , S. Sundar
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