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Inspired by the quantitative $K$-theory, in this paper, we introduce the coarse Baum-Connes conjecture with filtered coefficients which generalizes the original conjecture. There are two advantages for the conjecture with filtered…

Operator Algebras · Mathematics 2025-06-24 Jianguo Zhang

In this paper, we introduce and study the persistent approximation property for quantitative K-theory of filtered C*-algebras. In the case of crossed product C*-algebras, the persistent approximation property follows from the Baum-Connes…

Operator Algebras · Mathematics 2014-03-31 Hervé Oyono-Oyono , Guoliang Yu

We associate a non-commutative $C^*$-algebra with any locally finite simplicial complex. We determine the $K$-theory of these algebras and show that they can be used to obtain a conceptual explanation for the Baum-Connes conjecture.

Operator Algebras · Mathematics 2007-05-23 Joachim Cuntz

In this paper we give a simple proof of the maximality of dual coactions on full cross-sectional C*-algebras of Fell bundles over locally compact groups. As applications we extend certain exotic crossed-product functors in the sense of…

Operator Algebras · Mathematics 2015-07-22 Alcides Buss , Siegfried Echterhoff

In this paper, we develop a quantitative K-theory for filtered C*-algebras. Particularly interesting examples of filtered C*-algebras include group C*-algebras, crossed product C*-algebras and Roe algebras. We prove a quantitative version…

Operator Algebras · Mathematics 2012-04-17 Hervé Oyono-Oyono , Guoliang Yu

The basic notions and results of equivariant KK-theory concerning crossed products can be extended to the case of locally compact quantum groups. We recall these constructions and prove some usefull properties of subgroups and amalgamated…

Operator Algebras · Mathematics 2020-06-04 Roland Vergnioux

A crossed product functor is said to be injective if it takes injective morphisms to injective morphisms. In this paper we show that every locally compact group $G$ admits a maximal injective crossed product $A\mapsto A\rtimes_{\inj}G$.…

Operator Algebras · Mathematics 2020-10-07 Alcides Buss , Siegfried Echterhoff , Rufus Willett

We prove that if the classical Baum-Connes conjecture in complex K-theory is true (for a given discrete group G), then the conjecture is also true in the real case (for the same group G). The essential ingredients of the proof are the…

Operator Algebras · Mathematics 2016-09-07 Paul Baum , Max Karoubi

Let G be a finite group. We systematically exploit general homological methods in order to reduce the computation of G-equivariant KK-theory to topological equivariant K-theory. The key observation is that the functor assigning to a…

Operator Algebras · Mathematics 2016-05-11 Ivo Dell'Ambrogio

In this partly expository paper we compare three different categories of C*-algebras in which crossed-product duality can be formulated, both for actions and for coactions of locally compact groups. In these categories, the isomorphisms…

Operator Algebras · Mathematics 2016-03-16 S. Kaliszewski , Tron Omland , John Quigg

In this paper, we introduce a property of topological dynamical systems that we call finite dynamical complexity. For systems with this property, one can in principle compute the $K$-theory of the associated crossed product $C^*$-algebra by…

K-Theory and Homology · Mathematics 2022-10-13 Erik Guentner , Rufus Willett , Guoliang Yu

We define and compare two bivariant generalizations of the topological $K$-group $K^\top(G)$ for a topological group $G$. We consider the Baum-Connes conjecture in this context and study its relation to the usual Baum-Connes conjecture.

K-Theory and Homology · Mathematics 2011-10-18 Otgonbayar Uuye

We show that the Baum--Connes assembly map factors canonically through the unitary conjugation groupoid, which serves as a universal mediator among groupoid models that are Morita equivalent to a given transformation groupoid. This…

Operator Algebras · Mathematics 2026-03-24 Shih-Yu Chang

We provide a reference for basic categorial properties of the categories of (possibly non-unital) $\mathbb{C}$-linear $*$-categories or $C^{*}$-categories, and (not necessarily unit-preserving) functors. Generalizing the classical case of…

Operator Algebras · Mathematics 2021-12-13 Ulrich Bunke

We develop an approach, using what we call "tensor $D$ coaction functors", to the "$C$-crossed-product" functors of Baum, Guentner, and Willett. We prove that the tensor $D$ functors are exact, and identify the minimal such functor. This…

Operator Algebras · Mathematics 2023-06-14 S. Kaliszewski , Magnus B. Landstad , John Quigg

Using a combination of Atiyah-Segal ideas on one side and of Connes and Baum-Connes ideas on the other, we prove that the Twisted geometric K-homology groups of a Lie groupoid have an external multiplicative structure extending hence the…

K-Theory and Homology · Mathematics 2016-03-31 Noé Bárcenas , Paulo Carrillo Rouse , Mario Velásquez

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

Let $\left( 1\to N_m\to G_m\to Q_m\to 1 \right)_{m\in \mathbb{N}}$ be a sequence of extensions of finite groups such that their coarse disjoint unions have bounded geometry. In this paper, we show that if the coarse disjoint unions of…

K-Theory and Homology · Mathematics 2023-04-11 Jintao Deng , Qin Wang , Guoliang Yu

The paper studies the $K$-theoretic invariants of the crossed product $C^{*}$-algebras associated with an important family of homeomorphisms of the tori $\Bbb{T}^{n}$ called {\em Furstenberg transformations}. Using the Pimsner-Voiculescu…

Operator Algebras · Mathematics 2011-09-22 Kamran Reihani

Meyer and Nest showed that the Baum--Connes map is equivalent to a map on $K$-theory of two different crossed products. This approach is strongly categorial in method since its bases is to regard Kasparov's theory $KK^G$ as a triangulated…

K-Theory and Homology · Mathematics 2017-07-13 Bernhard Burgstaller