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We present a proof of non-amenability of R.Thompson's group F.

Group Theory · Mathematics 2021-09-15 Azer Akhmedov

We prove a fixed-point theorem that generalises and simplifies a number of results in the theory of $F$-contractions. We show that all of the previously imposed conditions on the operator can be either omitted or relaxed. Furthermore, our…

Classical Analysis and ODEs · Mathematics 2019-03-22 Sándor Kajántó , Andor Lukács

We show that pointlike sets are decidable for the pseudovariety of finite semigroups whose idempotent-generated subsemigroup is R-trivial. Notably, our proof is constructive: we provide an explicit relational morphism which computes the…

Group Theory · Mathematics 2022-04-21 Karsten Henckell , Samuel Herman

We present a study on strong t-continuity and measure of discontinuity on PN spaces. As an application, we prove a fixed point theorem for a self mapping on PN spaces by means of measure of discontinuity.

Functional Analysis · Mathematics 2007-06-12 Mohd Rafi

We first give simplified and corrected accounts of some results in \cite{PiRCP} on compactifications of pseudofinite groups. For instance, we use a classical theorem of Turing \cite{Turing} to give a simplified proof that any definable…

Logic · Mathematics 2025-06-18 Gabriel Conant , Ehud Hrushovski , Anand Pillay

In this paper, we establish a common fixed point theorem for two pairs of occasionally weakly compatible single and set-valued maps satisfying a strict contractive condition in a metric space. Our result extends many results existing in the…

Functional Analysis · Mathematics 2009-06-17 Hakima Bouhadjera , Christiane Godet-Thobie

We investigate the notion of relatively amenable topological action and show that the action of Thompson's group $T$ on $S^1$ is relatively amenable with respect to Thompson's group $F$. We use this to conclude that $F$ is exact if and only…

Group Theory · Mathematics 2021-09-28 Eduardo Scarparo

A topological group $G$ has the Approximate Fixed Point (AFP) property on a bounded convex subset $C$ of a locally convex space if every continuous affine action of $G$ on $C$ admits a net $(x_i)$, $x_i\in C$, such that…

Group Theory · Mathematics 2021-02-18 Cleon S. Barroso , Brice R. Mbombo , Vladimir G. Pestov

In this paper, among other things, we state and prove the mean ergodic theorem for amenable semigroup algebras.

Dynamical Systems · Mathematics 2007-07-16 Ali Ghaffari

Working in any model theoretic structure, we single out a class of definable bipartite graphs that admit definable, close to perfect matchings. We use this result to prove a strengthening of Tarski's theorem for the definable setting.

Logic · Mathematics 2025-07-14 Jana Maříková

Inner amenability is a bridge between amenability of an object and amenability of its operator algebras. It is an open problem of Ananantharman-Delaroche to decide whether all \'etale groupoids are inner amenable. Approximate lattices and…

Operator Algebras · Mathematics 2023-07-06 Gabriel Favre

We prove a generalization of Kannan's fixed point theorem, based on a recent result of Vittorino Pata.

General Topology · Mathematics 2012-12-18 Mitropam Chakraborty , S. K. Samanta

In this paper, we study some new fixed point results for self maps defined on partial metric type spaces. In particular, we give common fixed point theorems in the same setting. Some examples are given which illustrate the results.

General Topology · Mathematics 2018-09-12 Yaé Ulrich Gaba

In this note, we discuss some fixed point theorems for contractive self mappings defined on a $G$-metric spaces. More precisely, we give fised point theorems for mappings with a contractive iterate at a point.

General Topology · Mathematics 2017-02-24 Yaé Olatoundji Gaba

In this note we explain how Day's fixed point theorem can be used to conjugate certain groups of biLipschitz maps of a metric space into special subgroups like similarity groups. In particular, we use Day's theorem to establish Tukia-type…

Group Theory · Mathematics 2015-02-04 Tullia Dymarz , Xiangdong Xie

In this paper, using Kronecker's theorem, we discuss the set of common fixed points of an n-parameter continuous semigroup of mappings. We also discuss convergence theorems to a common fixed point of an n-parameter nonexpansive semigroup.

Functional Analysis · Mathematics 2007-05-23 Tomonari Suzuki

We study isometric actions of Steinberg groups on Hadamard manifolds. We prove some rigidity properties related to these actions. In Particular we show that every isometric action of $St_n(F_p\langle t_1,\ldots ,t_k \rangle)$ on Hadamard…

Group Theory · Mathematics 2019-12-24 Omer Lavy

We prove a fixed point theorem for the action of certain local monodromy groups on \'etale covers and use it to deduce lower bounds in essential dimension. In particular, we give more geometric proofs of many (but not all) of the results of…

Algebraic Geometry · Mathematics 2020-07-21 Patrick Brosnan , Najmuddin Fakhruddin

We provide a new characterization of amenability for countable groups, based on frame representations admitting almost invariant vectors. By relaxing the frame inequalities, thereby weakening amenability, we obtain a large class of…

Group Theory · Mathematics 2025-12-03 Dorin Ervin Dutkay , Catalin Georgescu , Gabriel Picioroaga

Notes that elaborate on the details of a Theorem of Shavgulidze that implies the amenability of R. J. Thompson's group F.

Group Theory · Mathematics 2009-09-19 Matthew G. Brin
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