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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 study general properties of exotic crossed-product functors and characterise those which extend to functors on equivariant C*-algebra categories based on correspondences. We show that every such functor allows the construction of a…

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

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 article continues the study of diagrams in the bicategory of \'etale groupoid correspondences. We prove that any such diagram has a groupoid model and that the groupoid model is a locally compact \'etale groupoid if the diagram is…

Category Theory · Mathematics 2024-10-29 Joanna Ko , Ralf Meyer

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

The homotopy theory of higher categorical structures has become a relevant part of the machinery of algebraic topology and algebraic K-theory, and this paper contains contributions to the study of the relationship between B\'enabou's…

Category Theory · Mathematics 2014-04-11 A. M. Cegarra , B. A. Heredia , J. Remedios

Sp\"ath showed that the Alperin-McKay conjecture in the representation theory of finite groups holds if the so-called inductive Alperin-McKay condition holds for all finite simple groups. In a previous article, we showed that the…

Representation Theory · Mathematics 2021-05-10 Lucas Ruhstorfer

We prove an analogue of the Baum-Connes conjecture for free orthogonal quantum groups. More precisely, we show that these quantum groups have a $ \gamma $-element and that $ \gamma = 1 $. It follows that free orthogonal quantum groups are $…

Operator Algebras · Mathematics 2011-07-12 Christian Voigt

Starting from the general concept of a Lie derivative of an arbitrary differentiable map, we develop a systematic theory of Lie differentiation in the framework of reductive G-structures P on a principal bundle Q. It is shown that these…

Differential Geometry · Mathematics 2007-05-23 Marco Godina , Paolo Matteucci

It is shown that certain lower semi-continuous maps from a paracompact space to the family of closed subsets of the bundle space of a Banach bundle admit continuous selections. This generalization of the theorem of Douady, dal…

Functional Analysis · Mathematics 2016-04-19 Aldo J. Lazar

Given an ample groupoid, we construct a spectral sequence with groupoid homology with integer coefficients on the second sheet, converging to the K-groups of the (reduced) groupoid C*-algebra, provided the groupoid has torsion-free…

K-Theory and Homology · Mathematics 2022-07-12 Valerio Proietti , Makoto Yamashita

A class of Weyl group equivariant $\ell$-adic complexes on a torus, called the central complexes, was introduced and studied in our previous work on Braverman-Kazhdan conjecture. In this note we show that the category of central complexes…

Representation Theory · Mathematics 2024-12-17 Tsao-Hsien Chen

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

We establish the splitting principle for differential K-theory, a refinement of topological K-theory that incorporates geometric data via differential forms. Using this principle, we prove that the differential $K^0$-ring associated to…

K-Theory and Homology · Mathematics 2026-02-04 Bo Liu , Xiaonan Ma

In studying the structure of derived categories of module categories of group algebras or their blocks, it is fundamental to classify support $\tau$-tilting modules. Koshio and Kozakai showed that the structure of support $\tau$-tilting…

Representation Theory · Mathematics 2023-11-29 Naoya Hiramae

We define an analytical index map and a topological index map for conical pseudomanifolds. These constructions generalize the analogous constructions used by Atiyah and Singer in the proof of their topological index theorem for a smooth,…

Operator Algebras · Mathematics 2010-05-18 Claire Debord , Jean-Marie Lescure , Victor Nistor

The Baum-Connes assembly map with coefficients $e_{\ast}$ and the Mishchenko-Kasparov assembly map with coefficients $\mu_{\ast}$ are two homomorphisms from the equivariant $K$-homology of classifying spaces of groups to the $K$-theory of…

Operator Algebras · Mathematics 2026-01-15 Jianguo Zhang

We introduce some generalized topological concepts to deal with union-closed families, and show that one can reduce the proof of Frankl's conjecture to some families of so-called supratopological spaces. We prove some results on the…

Combinatorics · Mathematics 2025-09-18 André Carvalho , António Machiavelo

Bernstein blocks of complex representations of p-adic reductive groups have been computed in a large amount of examples, in part thanks to the theory of types a la Bushnell and Kutzko. The output of these purely representation-theoretic…

Representation Theory · Mathematics 2016-07-28 Jean-François Dat

The equivariant coarse Baum-Connes conjecture interpolates between the Baum-Connes conjecture for a discrete group and the coarse Baum-Connes conjecture for a proper metric space. In this paper, we study this conjecture under certain…

K-Theory and Homology · Mathematics 2021-10-20 Jintao Deng , Benyin Fu , Qin Wang