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A C*-algebra is n-homogeneous (where n is finite) if every its nonzero irreducible representation acts on an n-dimensional Hilbert space. An elementary proof of Fell's characterization of n-homogeneous C*-algebras (by means of their…

Operator Algebras · Mathematics 2017-05-26 Piotr Niemiec

We define the $C^*$-algebra of quantum real projective space $\R P_q^2$, classify its irreducible representations and compute its $K$-theory. We also show that the $q$-disc of Klimek-Lesniewski can be obtained as a non-Galois…

Quantum Algebra · Mathematics 2007-05-23 Piotr M. Hajac , Rainer Matthes , Wojciech Szymanski

Let G be a finitely generated discrete group. The standard spectral triple on the group C*-algebra C*(G) is shown to admit the quantum group of orientation preserving isometries. This leads to new examples of compact quantum groups. In…

Operator Algebras · Mathematics 2015-05-18 Jyotishman Bhowmick , Adam Skalski

The quantum Euclidean spheres, $S_q^{N-1}$, are (noncommutative) homogeneous spaces of quantum orthogonal groups, $\SO_q(N)$. The *-algebra $A(S^{N-1}_q)$ of polynomial functions on each of these is given by generators and relations which…

K-Theory and Homology · Mathematics 2009-11-07 Eli Hawkins , Giovanni Landi

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

We consider the C*-algebras O_2^q and A_2^q generated, respectively, by isometries s_1, s_2 satisfying the relation s_1^* s_2 = q s_2 s_1^* with |q| < 1 (the deformed Cuntz relation), and by isometries s_1, s_2 satisfying the relation s_2…

Operator Algebras · Mathematics 2007-05-23 Palle E. T. Jorgensen , Daniil P. Proskurin , Yurii S. Samoilenko

We show that a C*-algebra generated by an irreducible representation of a finitely generated virtually nilpotent group satisfies the universal coefficient theorem and has real rank 0. This combines with previous joint work with Gillaspy and…

Operator Algebras · Mathematics 2024-08-16 Caleb Eckhardt

Two known $q$-deformed (or `quantum') $7$-spheres, both denoted $\mathbb{S}^7_q$ in the literature, may be distinguished by the presence or absence of symmetry under $\mathrm{SU}_q(2)$. The quaternionic version of $\mathbb{S}^7_q$ has been…

Quantum Algebra · Mathematics 2026-02-16 William J. Ugalde , Joseph C. Várilly

We investigate quantum lens spaces, $C(L_q^{2n+1}(r;\underline{m}))$, introduced by Brzezi\'nski-Szyma\'nski as graph $C^*$-algebras. We give a new description of $C(L_q^{2n+1}(r;\underline{m}))$ as graph $C^*$-algebras amending an error in…

Operator Algebras · Mathematics 2023-01-16 Thomas Gotfredsen , Sophie Emma Zegers

In this paper, we give a different proof of the fact that the $C^{*}$ algebra of the odd dimensional quantum spheres is a groupoid $C*}$ algebra. We use the theory of inverse semigroups to reconstruct the groupoid given by Sheu in [6].

Operator Algebras · Mathematics 2011-04-26 S. Sundar

We prove that any irreducible $*$-representation of $\mathrm{Pol}(\mathrm{Mat}_n)_q$ can be 'lifted' to an irreducible *-representation of $\mathbb{C}[SU_{2n}]_q$, this result is then used to show the existence of the universal enveloping…

Quantum Algebra · Mathematics 2018-03-26 Olof Giselsson

We discuss generalizations of the notion of i) the group of unitary elements of a (real or complex) finite dimensional C*-algebra, ii) gauge transformations and iii) (real) automorphisms, in the framework of compact quantum group theory and…

Quantum Algebra · Mathematics 2014-10-13 Jyotishman Bhowmick , Francesco D'Andrea , Biswarup Das , Ludwik Dabrowski

For $N\ge 4$ we present a series of *-homomorphisms $\varphi_n:C(S_N^+)\rightarrow B_n$ where $S_N^+$ is the quantum permutation group. They are not necessarily representations of the quantum group $S_N^+$ but they yield good operator…

Operator Algebras · Mathematics 2019-06-26 Stefan Jung , Moritz Weber

We compute the two-cocycles (or multipliers) of the free nilpotent groups of class $2$ and rank $n$ and give conditions for simplicity of the corresponding twisted group $C^*$-algebras. These groups are representation groups for…

Operator Algebras · Mathematics 2016-07-08 Tron Omland

The crystal limit C(K0) of the $q$-family of C*-algebras C(Kq) was introduced by Giri & Pal for all K=SU(n+1), n\geq 2. This article aims to prove that the crystal limits C(K0) have the property that the representations of C(Kq) give rise…

Operator Algebras · Mathematics 2025-04-23 Saikat Das , Ayan Dey

We show that C*-algebras generated by irreducible representations of finitely generated nilpotent groups satisfy the universal coefficient theorem of Rosenberg and Schochet. This result combines with previous work to show that these…

Operator Algebras · Mathematics 2023-07-19 Caleb Eckhardt , Elizabeth Gillaspy

In this paper we prove that several operator algebras are completely isomorphic to each other; e.g., the $C^*_\lambda(F_k)$, $k\geq 2$, the $C^*$-algebras generated by the regular left representation $\lambda:F_k\to B(\ell_2(F_k))$, are…

Functional Analysis · Mathematics 2008-02-03 Alvaro Arias

Let $\theta$ be a nondegenerate skew symmetric real $d$ by $d$ matrix, and let $A_{\theta}$ be the corresponding simple higher dimensional noncommutative torus. Suppose that $d$ is odd, or that $d$ is greater or equal to 4 and the entries…

Operator Algebras · Mathematics 2016-08-16 Benjamín Itzá-Ortiz , N. Christopher Phillips

In this note we analyze the C*-algebra associated with a branched covering both as a groupoid C*-algebra and as a Cuntz-Pimsner algebra. We determine conditions when the algebra is simple and purely infinite. We indicate how to compute the…

Operator Algebras · Mathematics 2007-05-23 Valentin Deaconu , Paul S. Muhly

To a graph $\Gamma$ one can associate a C^*-algebra $C^*(\Gamma)$ generated by isometries. Such $C^*$-algebras were studied recently by Crisp and Laca. They are a special case of the Toeplitz C^*-algebras $\mathcal{T}(G, P)$ associated to…

Operator Algebras · Mathematics 2007-11-07 Nikolay A. Ivanov