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We prove that the groups of orientation-preserving homeomorphisms and diffeomorphisms of $\mathbb{R}^n$ are boundedly acyclic, in all regularities. This is the first full computation of the bounded cohomology of a transformation group that…

Geometric Topology · Mathematics 2024-09-27 Francesco Fournier-Facio , Nicolas Monod , Sam Nariman , Alexander Kupers

Let G be an abelian topological group. The symbol \hat{G} denotes the group of all continuous characters \chi : G --> T endowed with the compact open topology. A subset E of G is said to be qc-dense in G provided that \chi(E) \subseteq…

General Topology · Mathematics 2012-05-07 Dikran Dikranjan , Dmitri Shakhmatov

We take the first steps towards a better understanding of continuous orbit equivalence, i.e., topological orbit equivalence with continuous cocycles. First, we characterise continuous orbit equivalence in terms of isomorphisms of C*-crossed…

Dynamical Systems · Mathematics 2015-03-06 Xin Li

We study the topology of circularly ordered sets. While the algebraic notion is classical, the general topological theory has received comparatively little attention. In this work we provide a self-contained topological exposition and…

General Topology · Mathematics 2026-04-27 Michael Megrelishvili

Let $G$ and $H$ be locally compact groups and consider their associate spaces of almost periodic functions $AP(G)$ and $AP(H)$. We investigate the continuous group homomorphisms induced by isometries of $AP(G)$ into $AP(H)$. Among others,…

Functional Analysis · Mathematics 2025-02-25 Salvador Hernández

In this paper we study topological cocycles for minimal homeomorphisms on a compact metric space. We introduce a notion of an essential range for topological cocycles with values in a locally compact group, and we show that this notion…

Dynamical Systems · Mathematics 2007-05-23 Gernot Greschonig , Ulrich Haboeck

Given a set $X$ and a family $G$ of self-maps of $X$, we study the problem of the existence of a non-discrete Hausdorff topology on $X$ with respect to which all functions $f\in G$ are continuous. A topology on $X$ with this property is…

General Topology · Mathematics 2014-12-04 Taras Banakh , Igor Protasov , Olga Sipacheva

Consider the following property of a topological group G: every continuous affine G-action on a Hilbert space with a bounded orbit has a fixed point. We prove that this property characterizes amenability for locally compact sigma-compact…

Group Theory · Mathematics 2015-08-12 Maxime Gheysens , Nicolas Monod

We prove that if $G$ is a group of automorphisms of a regular locally finite building which is closed in the compact-open topology and acts Weyl transitively on the building, then $G$ admits just one Hausdorff locally compact…

Group Theory · Mathematics 2014-11-06 Rupert McCallum

In this paper, we consider the continuity of the inverse in (strongly) paratopological gyrogroups. The conclusions are established as follows: (1) A compact Hausdorff paratopological gyrogroup $G$ is a topological gyrogroup. (2) A Hausdorff…

General Topology · Mathematics 2023-05-29 Ying-Ying Jin , Li-Hong Xie

We show that for topological groups and loop contractible coefficients the cohomology groups of continuous group cochains and of group cochains that are continuous on some identity neighbourhood are isomorphic. Moreover, we show a similar…

Algebraic Topology · Mathematics 2013-02-14 Martin Fuchssteiner , Christoph Wockel

Let $\mathbb{G}$ be a compact Hausdorff group acting on a compact Hausdorff space $X$, $\alpha$ an irreducible $\mathbb{G}$-representation, and $C(X)$ the $C^*$-algebra of complex-valued continuous functions on $X$. We prove that the…

Operator Algebras · Mathematics 2026-03-17 Alexandru Chirvasitu

If G is a countable discrete group acting linearly on a finite-dimensional vector space over any topological field, then the groups of coboundaries are closed for the product topology in all degrees, and hence the cohomology is reduced in…

Group Theory · Mathematics 2017-03-23 Tim Austin

Throughout this Abstract, $G$ is a topological Abelian group and $\hat{G}$ is the space of continuous homomorphisms from $G$ into $T$ in the compact-open topology. A dense subgroup $D$ of $G$ determines $G$ if the (necessarily continuous)…

General Topology · Mathematics 2007-05-23 W. W. Comfort , S. U. Raczkowski , F. Javier Trigos-Arrieta

A topological space is reversible if each continuous bijection of it onto itself is open. We introduce an analogue of this notion in the category of topological groups: A topological group G is g-reversible if every continuous automorphism…

Group Theory · Mathematics 2019-12-24 Vitalij Chatyrko , Dmitri Shakhmatov

A. Borel proved that, if a finite group $F$ acts effectively and continuously on a closed aspherical manifold $M$ with centerless fundamental group $\pi_1(M)$, then a natural homomorphism $\psi$ from $F$ to the outer automorphism group…

Differential Geometry · Mathematics 2009-05-09 Bin Xu

Given an extension $0\to V\to G\to Q\to1$ of locally compact groups, with $V$ abelian, and a compatible essentially bijective $1$-cocycle $\eta\colon Q\to\hat V$, we define a dual unitary $2$-cocycle on $G$ and show that the associated…

Operator Algebras · Mathematics 2023-12-04 Pierre Bieliavsky , Victor Gayral , Sergey Neshveyev , Lars Tuset

Suppose a locally compact group G acts freely and properly on a locally compact Hausdorff space X, and let gamma be the induced action on C_0(X). We consider a category in which the objects are C*-dynamical systems (A, G, alpha) for which…

Operator Algebras · Mathematics 2008-04-15 S. Kaliszewski , John Quigg , Iain Raeburn

A topological gyrogroup is a gyrogroup endowed with a topology such that the binary operation is jointly continuous and the inverse mapping is also continuous. It is shown that each compact subset of a topological gyrogroup with an…

General Topology · Mathematics 2022-09-07 Meng Bao , Xuewei Ling , Xiaoquan Xu

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