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We define the profinite completion of a C*-algebra, which is a pro-C*-algebra, as well as the pro-C*-algebra of a profinite group. We show that the continuous representations of the pro-C*-algebra of a profinite group correspond to the…

Operator Algebras · Mathematics 2012-04-23 Rachid El Harti , N. Christopher Phillips , Paulo R. Pinto

We study C*-irreducibility of inclusions of reduced twisted group C*-algebras and of reduced group C*-algebras. We characterize C*-irreducibility in the case of an inclusion arising from a normal subgroup, and exhibit many new examples of…

Operator Algebras · Mathematics 2023-01-31 Erik Bédos , Tron Omland

We examine the ranks of operators in semi-finite C*-algebras as measured by their densely defined lower semicontinuous traces. We first prove that a unital simple C*-algebra whose extreme tracial boundary is nonempty and finite contains…

Operator Algebras · Mathematics 2015-06-01 Aaron Tikuisis , Andrew Toms

We study $C^*$-algebras arising from $C^*$-correspondences, which was introduced by the author. We prove the gauge-invariant uniqueness theorem, and obtain conditions for our $C^*$-algebras to be nuclear, exact, or satisfy the Universal…

Operator Algebras · Mathematics 2007-05-23 Takeshi Katsura

In this paper, the $C^*$-algebra of the seven-dimensional un-decomposable nilpotent Lie group is characterized explicitly for the first time(see \cite{chin}). Furthermore, the topology of its spectrum is described as a preparation for the…

Operator Algebras · Mathematics 2024-10-23 Ghofrane Kardi

We solve a class of lifting problems involving approximate polynomial relations (soft polynomial relations). Various associated C*-algebras are therefore projective. The technical lemma we need is a new manifestation of Akemann and…

Operator Algebras · Mathematics 2014-01-14 Terry A. Loring , Tatiana Shulman

Motivated by Exel's inverse semigroup approach to combinatorial C*-algebras, in a previous work the authors defined an inverse semigroup associated with a labelled space. We construct a representation of the C*-algebra of a labelled space,…

Operator Algebras · Mathematics 2019-09-11 Giuliano Boava , Gilles G. de Castro , Fernando de L. Mortari

By using C*-correspondences and Cuntz-Pimsner algebras, we associate to every subshift (also called a shift space) $X$ a C*-algebra $O_X$, which is a generalization of the Cuntz-Krieger algebras. We show that $O_X$ is the universal…

Operator Algebras · Mathematics 2009-03-13 Toke Meier Carlsen

In this paper, we consider $\text{C}^*$-algebras with the ideal property (the ideal property unifies the simple and real rank zero cases). We define two categories related the invariants of the $\text{C}^*$-algebras with the ideal property.…

Operator Algebras · Mathematics 2017-05-30 Kun Wang

Let $S$ be a subsemigroup of a second countable locally compact group $G$, such that $S^{-1}S=G$. We consider the $C^*$-algebra $C^*_\delta(S)$ generated by the operators of translation by all elements of $S$ in $L^2(S)$. We show that this…

Operator Algebras · Mathematics 2021-01-06 Marat A. Aukhadiev , Yulia N. Kuznetsova

Motivated by the description of the C*-algebras of 5 dimensional nilpotent Lie groups as algebras of operator fields defined over their spectra, we introduce the family of C* -algebras with norm controlled dual limits and we show that the…

Group Theory · Mathematics 2013-09-27 Hedi Regeiba , Jean Ludwig

We study the universal C^*-algebras generated by n projections $p_1, >..., p_n$ subject to the relation $p_1+... p_n = \lambda 1$, $\lambda \in \mathbb R$. The questions of when these C^*-algebras are type I, nuclear or exact are…

Operator Algebras · Mathematics 2010-08-09 Tatiana Shulman

This is a survey of work in which the author was involved in recent years. We consider C*-algebras constructed from representations of one or several algebraic endomorphisms of a compact abelian group - or, dually, of a discrete abelian…

Operator Algebras · Mathematics 2015-12-04 Joachim Cuntz

For a torsion free finitely generated nilpotent group G we naturally associate four finite dimensional nilpotent Lie algebras over a field of characteristic zero. We show that if G is a relatively free group of some variery of nilpotent…

Group Theory · Mathematics 2009-03-10 C. Kofinas , V. Metaftsis , A. I. Papistas

Let $\Gamma$ be a discrete group. When $\Gamma$ is nonamenable, the reduced and full group $C$*-algebras differ and it is generally believed that there should be many intermediate $C$*-algebras, however few examples are known. In this paper…

Operator Algebras · Mathematics 2014-03-21 Matthew Wiersma

We define the notion of quantized function algebras at $q=0$ or crystallization of the $q$ deformations of the type $A_{n}$ compact Lie groups at the $C^*$-algebra level. The $C^{*}$-algebra $A_{n}(0)$ is defined as a universal…

Quantum Algebra · Mathematics 2024-09-17 Manabendra Giri , Arup Kumar Pal

For any nilpotent Lie group $G$ we provide a description of the image of its $C^*$-algebra through its operator-valued Fourier transform. Specifically, we show that $C^*(G)$ admits a finite composition series such that that the spectra of…

Operator Algebras · Mathematics 2015-05-27 Ingrid Beltita , Daniel Beltita , Jean Ludwig

We compute the generator rank of a subhomgeneous C*-algebra in terms of the covering dimension of the pieces of its primitive ideal space corresponding to irreducible representations of a fixed dimension. We deduce that every Z-stable…

Operator Algebras · Mathematics 2022-06-14 Hannes Thiel

We develop a theory of type semigroups for arbitrary twisted, not necessarily Hausdorff \'etale groupoids. The type semigroup is a dynamical version of the Cuntz semigroup. We relate it to traces, ideals, pure infiniteness, and stable…

Operator Algebras · Mathematics 2025-03-28 Bartosz K. Kwaśniewski , Ralf Meyer , Akshara Prasad

Suppose that A is a C*-algebra for which A is isomorphic to A tensor Z, where Z is the Jiang-Su algebra: a unital, simple, stably finite, separable, nuclear, infinite dimensional C*-algebra with the same Elliott invariant as the complex…

Operator Algebras · Mathematics 2010-11-24 Mikael Rordam
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