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We consider the isometry group of the infinite dimensional separable hyperbolic space with its Polish topology. This topology is given by the pointwise convergence. For non-locally compact Polish groups, some striking phenomena like…

Group Theory · Mathematics 2023-05-12 Bruno Duchesne

The article gives the second part of the treatise on Regular Algebraic $K$-theory (Sections V & VI) of the author. Regular algebraic $K$-theory for groups is a homology theory for discrete groups closely connected to (but different from)…

K-Theory and Homology · Mathematics 2024-10-11 Ulrich Haag

We study homological invariants of the Steinberg algebra $\mathcal{A}_k(\mathcal{G})$ of an ample groupoid $\mathcal{G}$ over a commutative ring $k$. For $\mathcal{G}$ principal or Hausdorff with…

K-Theory and Homology · Mathematics 2025-05-29 Guido Arnone , Guillermo Cortiñas , Devarshi Mukherjee

We consider the homology theory of \'etale groupoids introduced by Crainic and Moerdijk, with particular interest to groupoids arising from topological dynamical systems. We prove a K\"unneth formula for products of groupoids and a…

K-Theory and Homology · Mathematics 2025-08-19 Valerio Proietti , Makoto Yamashita

In this paper we present several algorithms related with the computation of the homology of groups, from a geometric perspective (that is to say, carrying out the calculations by means of simplicial sets and using techniques of Algebraic…

Algebraic Topology · Mathematics 2013-03-06 Ana Romero , Julio Rubio

We compute the homology of the space of equivariant loops on the classifying space of a simplicial monoid $M$ with anti-involution, provided $\pi_0 (M)$ is central in the homology ring of $M$. The proof is similar to McDuff and Segal's…

K-Theory and Homology · Mathematics 2020-11-11 Kristian Jonsson Moi

In the paper we discuss the algebraic structure of topological full group $[[T]]$ of a Cantor minimal system $(X,T)$. We show that the topological full group $[[T]]$ has the structure similar to a union of permutational wreath products of…

Group Theory · Mathematics 2012-07-04 Rostislav Grigorchuk , Konstantin Medynets

We study final group topologies and their relations to compactness properties. In particular, we are interested in situations where a colimit or direct limit is locally compact, a k_\omega-space, or locally k_\omega. As a first application,…

Group Theory · Mathematics 2015-03-27 Helge Glockner , Ralf Köhl , Tobias Hartnick

It is shown that a topological group G is topologically isomorphic to the isometry group of a (complete) metric space iff G coincides with its G-delta-closure in the Rajkov completion of G (resp. if G is Rajkov-complete). It is also shown…

Group Theory · Mathematics 2013-09-25 Piotr Niemiec

Bivariant (equivariant) K-theory is the standard setting for non-commutative topology. We may carry over various techniques from homotopy theory and homological algebra to this setting. Here we do this for some basic notions from…

K-Theory and Homology · Mathematics 2015-10-23 Ralf Meyer , Ryszard Nest

Motivated by the work of Cappell, Deturck, Gluch and Miller, we extend the notion of cohomology of harmonic forms (of a compact manifold with boundary) to the abstract setting of Hilbert complexes. Then, we present some geometric…

Differential Geometry · Mathematics 2025-12-17 Francesco Bei , Mauro Spreafico

By the work of Brodzki-Niblo-Nowak-Wright and Monod, topological amenability of a continuous group action can be characterized using uniformly finite homology groups or bounded cohomology groups associated to this action. We show that…

Dynamical Systems · Mathematics 2021-08-11 Yongle Jiang

The total homology of the loop space of the configuration space of ordered distinct n points in R^m has a structure of a Hopf algebra defined by the 4-term relations if m>2. We describe a relation of between the cohomology of this loop…

Algebraic Topology · Mathematics 2007-05-23 Toshitake Kohno

Let K >= 1 be a parameter. A K-approximate group is a finite set A in a (local) group which contains the identity, is symmetric, and such that A^2 is covered by K left translates of A. The main result of this paper is a qualitative…

Group Theory · Mathematics 2011-10-26 Emmanuel Breuillard , Ben Green , Terence Tao

We prove an asymptotic analog of the classical Hurewicz theorem on mappings which lower dimension. This theorem allows us to find sharp upper bound estimates for the asymptotic dimension of groups acting on finite dimensional metric spaces…

Group Theory · Mathematics 2007-05-23 G. C. Bell , A. N. Dranishnikov

The AH conjecture relates the low-dimensional homology groups of a groupoid with the abelianization of its topological full group. We show that transformation groupoids of minimal actions of the infinite dihedral group on the Cantor set…

Group Theory · Mathematics 2023-03-28 Eduardo Scarparo

We introduce a cochain complex for ample groupoids $\mathcal G$ using a flat resolution defining their homology with coefficients in $\mathbb Z$. We prove that the cohomology of this cochain complex with values in a $\mathcal G$-module $M$…

Operator Algebras · Mathematics 2025-08-05 Valentin Deaconu , Marius Ionescu

We prove explicit and elementary formulas for the group homology and cohomology of a finite group with coefficients in any module. We describe in elementary terms the cohomology algebra $H^*(G,k)$ as a graded algebra for a finite group $G$…

Group Theory · Mathematics 2015-07-16 Sergei O. Ivanov , Nikolay N. Mostovsky

A spectral sequence calculating the homology groups of some spaces of maps equivariant under compact group actions is described. For the main example, we calculate the rational homology groups of spaces of even and odd maps $S^m \to S^M$,…

Algebraic Topology · Mathematics 2021-07-01 Victor Vassiliev

We give a simple universal property of the multiplicative structure on the Thom spectrum of an $n$-fold loop map, obtained as a special case of a characterization of the algebra structure on the colimit of a lax $\mathcal{O}$-monoidal…

Algebraic Topology · Mathematics 2026-01-05 Omar Antolín-Camarena , Tobias Barthel