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We prove that a random group in the triangular density model has, for density larger than 1/3, fixed point properties for actions on $L^p$-spaces (affine isometric, and more generally $(2-2\epsilon)^{1/2p}$-uniformly Lipschitz) with $p$…

Group Theory · Mathematics 2019-08-21 Cornelia Drutu , John M. Mackay

We show that finitely generated groups which are Liouville and without infinite finite-dimensional linear representations must have a global fixed point whenever they act by isometry on a finite-dimensional complete CAT(0)-space. This…

Group Theory · Mathematics 2024-08-05 Hiroyasu Izeki , Anders Karlsson

We propose a fixed-point property for group actions on cones in topological vector spaces. In the special case of equicontinuous actions, we prove that this property always holds; this statement extends the classical Ryll-Nardzewski theorem…

Group Theory · Mathematics 2017-06-22 Nicolas Monod

Gromov showed that for fixed, arbitrarily large C, any uniformly C-Lipschitz affine action of a random group in his graph model on a Hilbert space has a fixed point. We announce a theorem stating that more general affine actions of the same…

Group Theory · Mathematics 2017-05-09 Shin Nayatani

We investigate fixed point properties for isometric actions of topological groups on a wide class of metric spaces, with a particular emphasis on Hilbert spaces. Instead of requiring the action to be continuous, we assume that it is…

Group Theory · Mathematics 2022-12-12 Romain Tessera , Jeroen Winkel

We prove that finitely generated amenable groups acting on CAT(0) spaces satisfy the following alternative: either every action on a geodesically complete CAT(0) space with bounded geometry (or finite dimension) has a global fixed point, or…

Group Theory · Mathematics 2026-03-30 Hiroyasu Izeki , Ran Ji , Anders Karlsson , Yunhui Wu

In this paper, we present a geometric condition for a family of CAT(0) spaces, which ensures that the Izeki-Nayatani invariants of spaces in the family are uniformly bounded from above by a constant strictly less than 1. Each element of…

Metric Geometry · Mathematics 2010-11-09 Tetsu Toyoda

We prove that a random group has fixed points when it isometrically acts on a CAT(0) cube complex. We do not assume that the action is simplicial.

Metric Geometry · Mathematics 2010-12-21 Koji Fujiwara , Tetsu Toyoda

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 prove that if a geodesically complete $\mathrm{CAT}(0)$ space $X$ admits a proper cocompact isometric action of a group, then the Izeki-Nayatani invariant of $X$ is less than $1$. Let $G$ be a finite connected graph, $\mu_1 (G)$ be the…

Metric Geometry · Mathematics 2015-10-06 Tetsu Toyoda

We present geometric conditions on a metric space $(Y,d_Y)$ ensuring that almost surely, any isometric action on $Y$ by Gromov's expander-based random group has a common fixed point. These geometric conditions involve uniform convexity and…

Group Theory · Mathematics 2019-02-20 Assaf Naor , Lior Silberman

Expanding maps with indifferent fixed points, a.k.a. intermittent maps, are popular models in nonlinear dynamics and infinite ergodic theory. We present a simple proof of the exactness of a wide class of expanding maps of [0,1], with…

Dynamical Systems · Mathematics 2017-09-04 Marco Lenci

We study uniform exponential growth of groups acting on CAT(0) cube complexes. We show that groups acting without global fixed points on CAT(0) square complexes either have uniform exponential growth or stabilize a Euclidean subcomplex.…

Group Theory · Mathematics 2023-04-05 Radhika Gupta , Kasia Jankiewicz , Thomas Ng

For a finite and positive measure space $(\Omega,\Sigma,\mu)$ and any weakly compact convex subset of $L\sp\infty(\Omega,\Sigma,mu)$, a fixed point theorem for a class of nonexpansive self-mappings is proved. An analogous result is obtained…

Functional Analysis · Mathematics 2007-05-23 Cleon S. Barroso

For a finitely generated free group F_n, of rank at least 2, any finite subgroup of Out(F_n) can be realized as a group of automorphisms of a graph with fundamental group F_n. This result, known as Out(F_n) realization, was proved by…

Group Theory · Mathematics 2007-05-23 Matt Clay

A well-known result of W. Ray asserts that if $C$ is an unbounded convex subset of a Hilbert space, then there is a nonexpansive mapping $T$: $C\to C$ that has no fixed point. In this paper we establish some common fixed point properties…

Functional Analysis · Mathematics 2020-01-23 Anthony T. -M. Lau , Yong Zhang

Firmly nonexpansive mappings play an important role in metric fixed point theory and optimization due to their correspondence with maximal monotone operators. In this paper we do a thorough study of fixed point theory and the asymptotic…

Functional Analysis · Mathematics 2012-11-26 David Ariza-Ruiz , Laurentiu Leustean , Genaro Lopez-Acedo

We study the fixed point theory of n-valued maps of a space X using the fixed point theory of maps between X and its configuration spaces. We give some general results to decide whether an n-valued map can be deformed to a fixed point free…

Geometric Topology · Mathematics 2017-02-17 Daciberg Lima Gonçalves , John Guaschi

We consider expansive group actions on a compact metric space containing a special fixed point denoted by $0$, and endomorphisms of such systems whose forward trajectories are attracted toward $0$. Such endomorphisms are called…

Dynamical Systems · Mathematics 2019-02-18 Ville Salo , Ilkka Törmä

In this paper we study fixed point properties for semitopological semigroup of nonexpansive mappings on a bounded closed convex subset of a Banach space. We also study a Schauder fixed point property for a semitopological semigroup of…

Functional Analysis · Mathematics 2012-07-20 A. T. -M. Lau , Yong Zhang
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