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We present an alternative approach to the result of Guentner, Higson, and Weinberger concerning the Baum-Connes conjecture for finitely generated subgroups of SL(2,C). Using finite-dimensional methods, we show that the Baum-Connes assembly…

Group Theory · Mathematics 2007-12-24 Dmitry Matsnev

We document some versions, in real K-theory, of well-known properties of the coarse assembly map in complex K-theory. These results are well-known, but difficult to find in the literature.

K-Theory and Homology · Mathematics 2013-08-13 John Roe

We present a geometric approach to the Baum-Connes conjecture with coefficients for Gromov monster groups via a theorem of Khoskham and Skandalis. Secondly, we use recent results concerning the a-T-menability at infinity of large girth…

K-Theory and Homology · Mathematics 2014-09-23 Martin Finn-Sell

Let $G$ and $H$ be finitely generated groups. In this paper, we prove the quantitative coarse Baum--Connes conjecture for the free product $G* H$ under the assumption that the conjecture holds for both $G$ and $H$.

Operator Algebras · Mathematics 2026-05-07 Jintao Deng , Ryo Toyota

In this article, we introduce the notion of a functor on coarse spaces being coarsely excisive- a coarse analogue of the notion of a functor on topological spaces being excisive. Further, taking cones, a coarsely excisive functor yields a…

Algebraic Topology · Mathematics 2014-10-01 Paul D. Mitchener

We investigate when Isomorphism Conjectures, such as the ones due to Baum-Connes, Bost and Farrell-Jones, are stable under colimits of groups over directed sets (with not necessarily injective structure maps). We show in particular that…

K-Theory and Homology · Mathematics 2007-05-23 Arthur Bartels , Siegfried Echterhoff , Wolfgang Lueck

We define bounded cohomology of $t$-discrete measured groupoids with coefficients into measurable bundles of Banach spaces. Our approach via homological algebra extends the classic theory developed by Ivanov and by Monod. As a consequence,…

Algebraic Topology · Mathematics 2025-03-31 Filippo Sarti , Alessio Savini

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 classical Baum-Connes assembly map is quantitatively an isomorphism for a class of lacunary hyperbolic groups, and we explain how to see that this class contains many examples of groups that contain graph sequences of large…

Group Theory · Mathematics 2026-05-14 Martin Finn-Sell

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

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

We consider the equivariant K-theory of a real semisimple Lie group which acts on the (complex) flag variety of its complexification group. We construct an assemble map in the framework of KK-theory and then we prove that it is an…

K-Theory and Homology · Mathematics 2021-03-09 Zhaoting Wei

In this paper, we investigate the $L^{p}$ coarse Baum-Connes conjecture for $p\in [1,\infty)$ via $C_{0}$ coarse structure, which is a refinement of the bounded coarse structure on a metric space. We prove that the $C_{0}$ version of the…

Functional Analysis · Mathematics 2026-04-14 Hang Wang , Yanru Wang , Jianguo Zhang , Dapeng Zhou

We construct the geometric Baum-Connes assembly map for twisted Lie groupoids, that means for Lie groupoids together with a given groupoid equivariant $PU(H)-$principle bundle. The construction is based on the use of geometric deformation…

K-Theory and Homology · Mathematics 2016-02-29 Paulo Carrillo Rouse , Bai-Ling Wang

In this note we set a configuration space description of the equivariant connective K-homology groups with coefficients in a unital C*-algebra for proper actions. Over this model we define a connective assembly map and prove that in this…

K-Theory and Homology · Mathematics 2019-02-04 Mario Velásquez

This paper constitutes a first step in the author's program to investigate the question of when a homotopy of 2-cocycles $\omega = \{\omega_t\}_{t \in [0,1]}$ on a locally compact Hausdorff groupoid $\mathcal{G}$ induces an isomorphism of…

Operator Algebras · Mathematics 2014-09-09 Elizabeth Gillaspy

Suppose $\mathcal{G}$ is a second-countable locally compact Hausdorff \'{e}tale groupoid, $G$ is a discrete group containing a unital subsemigroup $P$, and $c:\mathcal{G}\rightarrow G$ is a continuous cocycle. We derive conditions on the…

Operator Algebras · Mathematics 2019-06-10 Lisa Orloff Clark , James Fletcher

We introduce a notion of fibred coarse embedding into Hilbert space for metric spaces, which is a generalization of Gromov's notion of coarse embedding into Hilbert space. It turns out that a large class of expander graphs admit such an…

K-Theory and Homology · Mathematics 2012-08-23 Xiaoman Chen , Qin Wang , Guoliang Yu

Inspired by group cohomology, we define several coarse topological invariants of metric spaces. We define the coarse cohomological dimension of a metric space, and demonstrate that if G is a countable group, then the coarse cohomological…

Group Theory · Mathematics 2024-11-08 Alexander Margolis

The Baum-Connes conjecture predicts that a certain assembly map is an isomorphism. We identify the homotopy theoretical construction of the assembly map by Davis and L\"uck with the category theoretical construction by Meyer and Nest. This…

K-Theory and Homology · Mathematics 2022-02-01 Julian Kranz