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We consider the 1-harmonic flow of maps from a bounded domain into a submanifold of a Euclidean space, i.e. the gradient flow of the total variation functional restricted to maps taking values in the manifold. We restrict ourselves to…

Analysis of PDEs · Mathematics 2017-12-08 Lorenzo Giacomelli , Michał Łasica , Salvador Moll

We develop a class of homeomorphisms on a compact homogeneous space of a transitive group action and show how the class sheds new light on a decomposition problem. We further use this class to show that every such homogeneous space in a…

Functional Analysis · Mathematics 2023-08-22 Samuel A. Hokamp

Equationally compact subgroups of countable groups were introduced by Banaschewski. For all known cases the orbit closure of such a subgroup is a countable subset in the space of subgroups and has finite Cantor-Bendixson rank. We show that…

Group Theory · Mathematics 2016-08-19 Gabor Elek , Konrad Krolicki

Considering the space of closed subsets of $\mathbb{R}^d$, endowed with the Chabauty-Fell topology, and the affine action of $SL_d(\mathbb{R})\ltimes\mathbb{R}^d$, we prove that the only minimal subsystems are the fixed points…

Dynamical Systems · Mathematics 2015-10-27 Omri Solan , Yaar Solomon , Barak Weiss

We prove that every irreducible component of the fixed point variety under the action of $d$-th roots of unity in a smooth Caloger-Moser space is isomorphic to a Calogero-Moser space associated with another reflection group.

Representation Theory · Mathematics 2020-06-29 Cédric Bonnafé , Ruslan Maksimau

We prove that if the universal minimal flow of a Polish group $G$ is metrizable and contains a $G_\delta$ orbit $G \cdot x_0$, then it is isomorphic to the completion of the homogeneous space $G/G_{x_0}$ and show how this result translates…

Dynamical Systems · Mathematics 2018-10-29 Julien Melleray , Lionel Nguyen Van Thé , Todor Tsankov

We study properties of the Weyl pseudometric associated with an action of a countable amenable group on a compact metric space. We prove that the topological entropy and the number of minimal subsets of the closure of an orbit are both…

Dynamical Systems · Mathematics 2018-08-01 Martha Łącka , Marta Straszak

We show that if a flat group scheme acts properly, with finite stabilizers, on an algebraic space, then a quotient exists as a separated algebraic space. More generally we show any flat groupid for which the family of stabilizers is finite…

alg-geom · Mathematics 2008-02-03 Sean Keel , Shigefumi Mori

We present a uniform version of a result of M. Gromov on the surjunctivity of maps commuting with expansive group actions and discuss several applications. We prove in particular that for any group $\Gamma$ and any field $\K$, the space of…

Group Theory · Mathematics 2011-09-15 Tullio Ceccherini-Silberstein , Michel Coornaert

It is introduced an analogue of the orbit-breaking subalgebra for the case of free flows on locally compact metric spaces, which has a natural approximate structure in terms of a fixed point and any nested sequence of central slices around…

Operator Algebras · Mathematics 2022-12-13 Jacopo Bassi

We prove that every uniform approximate homomorphism from a discrete amenable group into a symmetric group is uniformly close to a homomorphism into a slightly larger symmetric group. That is, amenable groups are uniformly flexibly stable…

Group Theory · Mathematics 2020-05-15 Oren Becker , Michael Chapman

We prove an effective variant of the Kazhdan-Margulis theorem generalized to stationary actions of semisimple groups over local fields: the probability that the stabilizer of a random point admits a non-trivial intersection with a small…

Group Theory · Mathematics 2021-03-23 Tsachik Gelander , Arie Levit , Gregory Margulis

In this paper, we extend a Ma\~n\'e's famous result on expansive homeomorphisms, originally presented in [17], to the setting of flows. Specifically, we provide a complete characterization of minimal expansive flows without fixed points on…

Dynamical Systems · Mathematics 2025-08-22 Alfonso Artigue , Elias Rego

A group $\Gamma$ is said to be uniformly HS stable if any map $\varphi : \Gamma \to U(n)$ that is almost a unitary representation (w.r.t. the Hilbert Schmidt norm) is close to a genuine unitary representation of the same dimension. We…

Group Theory · Mathematics 2023-01-31 Danil Akhtiamov , Alon Dogon

Continuous actions of topological groups on compact Hausdorff spaces $X$ are investigated which induce almost periodic functions in the corresponding commutative C*-algebra. The unique invariant mean on the group resulting from averaging…

Operator Algebras · Mathematics 2009-03-11 M. Frank , V. Manuilov , E. Troitsky

In this paper, we study the regularized mean curvature flow starting from invariant hypersurfaces in a Hilbert space equipped with an isometric almost free Hilbert Lie group action whose orbits are minimal regularizable submanifolds, where…

Differential Geometry · Mathematics 2018-02-26 Naoyuki Koike

Let $G$ be a reductive algebraic group over an algebraically closed field and let $V$ be a quasi-projective $G$-variety. We prove that the set of points $v\in V$ such that ${\rm dim}(G_v)$ is minimal and $G_v$ is reductive is open. We also…

Group Theory · Mathematics 2015-10-12 Benjamin Martin

We prove that every expanding minimal semigroup action of $C^1$ diffeomorphisms of a compact manifold (resp. $C^{1+\alpha}$ conformal) is robustly minimal (resp. ergodic with respect to Lebesgue measure). We also show how, locally, a…

Dynamical Systems · Mathematics 2018-01-04 Pablo G. Barrientos , Abbas Fakhari , Dominique Malicet , Ali Sarizadeh

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 show that every hyperbolic group has a proper uniformly Lipschitz affine action on a subspace of an $L^1$ space. We also prove that every acylindrically hyperbolic group has a uniformly Lipschitz affine action on such a space with…

Group Theory · Mathematics 2023-10-24 Ignacio Vergara