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We introduce a bivariant version of the Cuntz semigroup as equivalence classes of order zero maps generalizing the ordinary Cuntz semigroup. The theory has many properties formally analogous to KK-theory including a composition product. We…

Operator Algebras · Mathematics 2016-02-08 Joan Bosa , Gabriele Tornetta , Joachim Zacharias

In this note we show that a combinatorial model of Kirchberg algebras in the UCT, namely the Katsura algebras O_{AB}, can be expressed both as groupoid C*-algebras and as inverse semigroup crossed products. We use this picture to obtain…

Operator Algebras · Mathematics 2013-04-24 Ruy Exel , Enrique Pardo

In this paper we describe the C*-algebras associated to the Baumslag-Solitar groups with the ordering defined by the usual presentations. These are Morita equivalent to the crossed product C*-algebras obtained by letting the group act on…

Operator Algebras · Mathematics 2012-11-16 Jack Spielberg

We compute the group homology, the topological K-theory of the reduced C^*-algebra, the algebraic K-theory and the algebraic L-theory of the group ring of the semi-direct product of the three-dimensional discrete Heisenberg group by Z/4.…

K-Theory and Homology · Mathematics 2014-11-11 Wolfgang Lueck

We study C*-algebras associated with subsemigroups of groups. For a large class of such semigroups including positive cones in quasi-lattice ordered groups and left Ore semigroups, we describe the corresponding semigroup C*-algebras as…

Operator Algebras · Mathematics 2012-05-14 Xin Li

In this paper, we apply the theory of inverse semigroups to the $C^{*}$-algebra $U[\mathbb{Z}]$ considered in \cite{Cuntz}. We show that the $C^{*}$-algebra $U[\mathbb{Z}]$ is generated by an inverse semigroup of partial isometries. We…

Operator Algebras · Mathematics 2011-04-13 S. Sundar

We define united K-theory for real C*-algebras, generalizing Bousfield's topological united K-theory. United K-theory incorporates three functors -- real K-theory, complex K-theory, and self-conjugate K-theory -- and the natural…

Operator Algebras · Mathematics 2007-05-23 Jeffrey L. Boersema

This paper investigates the $\mathrm{K}$-theory of twisted groupoid $\mathrm{C}^*$-algebras. It is shown that a homotopy of twists on an ample groupoid satisfying the Baum-Connes conjecture with coefficients gives rise to an isomorphism…

Operator Algebras · Mathematics 2019-04-25 Christian Bönicke

In this paper we show that the universal C*-algebra satisfying the Cuntz-Li relations is generated by an inverse semigroup of partial isometries. We apply Exel's theory of tight representations to this inverse semigroup. We identify the…

Operator Algebras · Mathematics 2012-04-02 S. Sundar

We give a new definition of the semigroup C*-algebra of a left cancellative semigroup, which resolves problems of the construction by X. Li. Namely, the new construction is functorial, and the independence of ideals in the semigroup does…

Operator Algebras · Mathematics 2019-05-07 Marat Aukhadiev

C. Schochet shows K\"unneth theorem for the $C^*$-algebras in the smallest class of nuclear $C^*$-algebras which contains the separable Type I algebras and is closed under some operations. We calculate the $K$-theory for the crossed product…

Operator Algebras · Mathematics 2015-02-17 Issei Ohhashi

We study the C*-algebra crossed product $C_0(X)\rtimes G$ of a locally compact group $G$ acting properly on a locally compact Hausdorff space $X$. Under some mild extra conditions, which are automatic if $G$ is discrete or a Lie group, we…

K-Theory and Homology · Mathematics 2010-12-24 Heath Emerson , Siegfried Echterhoff

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

Let H(R,q) be an affine Hecke algebra with a positive parameter function q. We are interested in the topological K-theory of H(R,q), that is, the K-theory of its C*-completion C*_r (R,q). We will prove that $K_* (C*_r (R,q))$ does not…

K-Theory and Homology · Mathematics 2018-07-25 Maarten Solleveld

We compute K-theory for the reduced group C*-algebras of generalized Lamplighter groups.

K-Theory and Homology · Mathematics 2020-07-07 Xin Li

We prove that the category of abstract Cuntz semigroups is bicomplete. As a consequence, the category admits products and ultraproducts. We further show that the scaled Cuntz semigroup of the (ultra)product of a family of C*-algebras agrees…

Operator Algebras · Mathematics 2020-05-27 Ramon Antoine , Francesc Perera , Hannes Thiel

In this article we give a characterisation of the Baum-Connes assembly map with coefficients. The technical tools needed are the K-theory of C*-categories, and equivariant KK-theory in the world of groupoids.

K-Theory and Homology · Mathematics 2007-05-23 Paul D. Mitchener

We provide inverse semigroup and groupoid models for the Toeplitz and Cuntz-Krieger algebras of finitely aligned higher-rank graphs. Using these models, we prove a uniqueness theorem for the Cuntz-Krieger algebra.

Operator Algebras · Mathematics 2007-05-23 Cynthia Farthing , Paul S. Muhly , Trent Yeend

We construct reduced and full semigroup C*-algebras for left cancellative semigroups. Our new construction covers particular cases already considered by A. Nica and also Toeplitz algebras attached to rings of integers in number fields due…

Operator Algebras · Mathematics 2012-02-23 Xin Li

In a recent paper, Pardo and the first named author introduced a class of C*-algebras which which are constructed from an action of a group on a graph. This class was shown to include many C*-algebras of interest, including all Kirchberg…

Operator Algebras · Mathematics 2014-06-30 Ruy Exel , Charles Starling