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The main goal of this article is to bring together the theories of holomorphic iteration in the unit disc and semigroups of holomorphic functions. We develop a technique that allows us to partially embed the orbit of a holomorphic self-map…

Complex Variables · Mathematics 2025-11-25 Argyrios Christodoulou , Konstantinos Zarvalis

We introduce an equivariant version of the Cuntz semigroup, that takes an action of a compact group into account. The equivariant Cuntz semigroup is naturally a semimodule over the representation semiring of the given group. Moreover, this…

Operator Algebras · Mathematics 2018-01-08 Eusebio Gardella , Luis Santiago

We establish new results and introduce new methods in the theory of measurable orbit equivalence, using bounded cohomology of group representations. Our rigidity statements hold for a wide (uncountable) class of groups arising from negative…

Group Theory · Mathematics 2007-05-23 Nicolas Monod , Yehuda Shalom

This paper constructs a foundation to analyze semi-group actions, group actions, filtrations, and decompositions in a unified manner. In fact, though the studies of decomposition can be applied to foliated spaces and group actions, they can…

Dynamical Systems · Mathematics 2023-08-16 Tomoo Yokoyama

We study equivariant projective compactifications of reductive groups obtained by closing the image of a group in the space of operators of a projective representation. We describe the structure and the mutual position of their orbits under…

Algebraic Geometry · Mathematics 2015-06-26 Dmitri A. Timashev

We define the orbit morphism of partial dynamical systems and prove that an orbit morphism being an isomorphism in the category of partial dynamical systems and orbit morphisms is equivalent to the existence of a continuous orbit…

Operator Algebras · Mathematics 2024-12-06 Gilles G. de Castro , Eun Ji Kang

Let G be a group and let M be a CAT(0) proper metric space (e.g. a simply connected complete Riemannian manifold of non-positive sectional curvature or a locally finite tree). Isometric actions of G on M are (by definition) points in the…

Group Theory · Mathematics 2007-05-23 Robert Bieri , Ross Geoghegan

We consider a finitely generated group acting minimally on a compact space by homeomorphsims, and assume that the Schreier graph of at least one orbit is quasi-isometric to a line. We show that the topological full group of such an action…

Group Theory · Mathematics 2021-01-07 Nóra Gabriella Szőke

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

We study polar actions with horizontal sections on the total space of certain principal bundles $G/K\to G/H$ with base a symmetric space of compact type. We classify such actions up to orbit equivalence in many cases. In particular, we…

Differential Geometry · Mathematics 2011-03-07 Marco Mucha

We construct a finitely presented, infinite, simple group that acts by homeomorphisms on the circle, but does not admit a non-trivial action by $C^1$-diffeomorphisms on the circle. The group emerges as a group of piecewise projective…

Group Theory · Mathematics 2019-07-03 Yash Lodha

We study hyperpolar actions on reducible symmetric spaces of the compact type. Our main result is that an indecomposable hyperpolar action on a symmetric space of the compact type is orbit equivalent to a Hermann action or of cohomogeneity…

Differential Geometry · Mathematics 2015-03-05 Andreas Kollross

The article is devoted to a structure of topological spaces related with topological quasigroups. Regular and complete spaces over topological quasigroups are studied. Separations and embeddings are also investigated for them. Their…

Group Theory · Mathematics 2023-12-29 S. V. Ludkowski

We explore two properties of backward orbits under semigroups of holomorphic self-maps in the unit disk. First, we prove that regular backward orbits are quasi-geodesics for the hyperbolic distance of the unit disk. Then, we show that…

Complex Variables · Mathematics 2022-10-04 Konstantinos Zarvalis

The purpose of this note is twofold. In the first part we observe that two finitely generated non-amenable groups are quasi-isometric if and only if they admit topologically orbit equivalent Cantor minimal actions. In particular, free…

Dynamical Systems · Mathematics 2017-06-21 Kostya Medynets , Roman Sauer , Andreas Thom

In the first part of the paper, we introduce notions of asymptotic continuous orbit equivalence and asymptotic conjugacy in Smale spaces and characterize them in terms of their asymptotic Ruelle algebras with their dual actions. In the…

Operator Algebras · Mathematics 2018-07-27 Kengo Matsumoto

We show that all countable subsets of any pseudocompact quasitopological group in the form of a Korovin orbit are closed, discrete, and $C^\ast$-embedded. Consequently, any infinite pseudocompact Korovin orbit is not homeomorphic to a…

General Topology · Mathematics 2023-08-22 Evgenii Reznichenko , Mikhail Tkachenko

We define the orbit category for transitive topological groupoids and their equivariant CW-complexes. By using these constructions we define equivariant Bredon homology and cohomology for actions of transitive topological groupoids. We show…

Algebraic Topology · Mathematics 2019-11-11 Carla Farsi , Laura Scull , Jordan Watts

We study smooth locally free actions of ${\mathbb R}^n$ on manifolds $M$ of dimension $n+1$. We are interested in compact orbits and in compact actions: actions with all orbits compact. Given a compact orbit in a neighborhood of compact…

Dynamical Systems · Mathematics 2025-06-18 Carlos Gustavo Moreira , Nicolau C. Saldanha

We study mean equicontinuous actions of locally compact $\sigma$-compact amenable groups on compact metric spaces. In this setting, we establish the equivalence of mean equicontinuity and topo-isomorphy to the maximal equicontinuous factor…

Dynamical Systems · Mathematics 2019-10-15 Gabriel Fuhrmann , Maik Gröger , Daniel Lenz