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We show that every unitary representation of a solvable discrete virtually nilpotent group G is quasidiagonal. Roughly speaking, this says that every unitary representation of G approximately decomposes as a direct sum of finite dimensional…

Operator Algebras · Mathematics 2014-01-23 Caleb Eckhardt

There is a long-standing problem of algebra to extend the symmetric monoidal structure of abelian groups, given by the tensor product, to a non abelian setting. In this paper we show that such an extension is possible. Morover our non…

Category Theory · Mathematics 2007-05-23 H. -J. Baues , M. Jibladze , T. Pirashvili

We introduce the decomposition rank, a notion of covering dimension for nuclear C^*-algebras. The decomposition rank generalizes ordinary covering dimension and has nice permanence properties; in particular, it behaves well with respect to…

Operator Algebras · Mathematics 2007-05-23 Eberhard Kirchberg , Wilhelm Winter

We investigate relations on elements in C*-algebras, including *-polynomial relations, order relations and all relations that correspond to universal C*-algebras. We call these C*-relations and define them axiomatically. Within these are…

Operator Algebras · Mathematics 2010-12-30 Terry A. Loring

Different (fibrewise) amalgamated products of continuous C*-bundles have been studied over the last years, one of the main question being to know when these amalgamated products are continuous C*-bundles. In order to gather these approaches…

Operator Algebras · Mathematics 2008-03-03 Etienne Blanchard

Examples of simple, separable, unital, purely infinite $C^*$--algebras are constructed, including: (1) some that are not approximately divisible; (2) those that arise as crossed products of any of a certain class of $C^*$--algebras by any…

funct-an · Mathematics 2016-08-31 Kenneth J. Dykema , Mikael Rordam

We define E-theory for separable C*-algebras over second countable topological spaces and establish its basic properties. This includes an approximation theorem that relates the E-theory over a general space to the E-theories over finite…

K-Theory and Homology · Mathematics 2015-10-23 Marius Dadarlat , Ralf Meyer

Given two algebras A and B, sometimes assumed to be C*-algebras, we consider the question of putting algebra or C*-algebra structures on the tensor product A\otimes B. In the C*-case, assuming B to be two-dimensonal, we characterize all…

Operator Algebras · Mathematics 2012-04-03 R. Exel

We define and systematically study nonassociative C*-algebras as C*-algebras internal to a topological tensor category. We also offer a concrete approach to these C*-algebras, as G-invariant, norm closed *-subalgebras of bounded operators…

Quantum Algebra · Mathematics 2011-02-04 P. Bouwknegt , K. Hannabuss , V. Mathai

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

In this paper, we characterize $\ell$-open and $\ell$-closed $C^*$-algebras and deduce that $\ell$-open $C^*$-algebras are $\ell$-closed, as conjectured by Blackadar. Moreover, we show that a commutative unital $C^*$-algebra is $\ell$-open…

Operator Algebras · Mathematics 2024-01-31 Dolapo Oyetunbi , Aaron Tikuisis

We show that semigroup C*-algebras are groupoid C*-algebras.

Operator Algebras · Mathematics 2019-06-14 Hui Li

We study the class of pseudocompact C*-algebras, which are the logical limits of finite-dimensional C*-algebras. The pseudocompact C*-algebras are unital, stably finite, real rank zero, stable rank one, and tracial. We show that the…

Operator Algebras · Mathematics 2016-09-26 Stephen Hardy

Algebras associated with Quantum Electrodynamics and other gauge theories share some mathematical features with T-duality Exploiting this different perspective and some category theory, the full algebra of fermions and bosons can be…

High Energy Physics - Theory · Physics 2010-11-02 Keith C. Hannabuss

We consider three notions of divisibility in the Cuntz semigroup of a C*-algebra, and show how they reflect properties of the C*-algebra. We develop methods to construct (simple and non-simple) C*-algebras with specific divisibility…

Operator Algebras · Mathematics 2014-02-26 Leonel Robert , Mikael Rordam

This survey aims to highlight some of the consequences that representable (and continuous) functionals have in the framework of Banach quasi *-algebras. In particular, we look at the link between the notions of *-semisimplicity and full…

Functional Analysis · Mathematics 2020-02-21 Maria Stella Adamo

We study the C*-algebra crossed-product of the closed unit disk by the action of one of its conformal automorphisms. After classifying the conformal automorphisms up to topological conjugacy, we investigate, for each class, the irreducible…

Operator Algebras · Mathematics 2011-10-10 Man-Duen Choi , Frederic Latremoliere

In the theory of C*-algebras, interesting noncommutative structures arise as deformations of the tensor product. For instance, the rotation algebra may be seen as a scalar twist deformation of the tensor product of the functions on the…

Operator Algebras · Mathematics 2013-03-04 Moritz Weber

We study the ideal structure of $C^*$-algebras arising from $C^*$-correspondences. We prove that gauge-invariant ideals of our $C^*$-algebras are parameterized by certain pairs of ideals of original $C^*$-algebras. We show that our…

Operator Algebras · Mathematics 2007-05-23 Takeshi Katsura

We describe the $C^*$-algebra of an $E$-unitary or strongly 0-$E$-unitary inverse semigroup as the partial crossed product of a commutative $C^*$-algebra by the maximal group image of the inverse semigroup. We give a similar result for the…

Operator Algebras · Mathematics 2015-12-08 David Milan , Benjamin Steinberg