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If $(X,d)$ is a Polish metric space of dimension $0$, then by Wadge's lemma, no more than two Borel subsets of $X$ can be incomparable with respect to continuous reducibility. In contrast, our main result shows that for any metric space…

Logic · Mathematics 2017-06-14 Philipp Schlicht

Given an ergodic probability measure preserving dynamical system $\G\acts (X,\mu)$, where $\G$ is a finitely generated countable group, we show that the asymptotic growth of the number of finite models for the dynamics, in the sense of…

Dynamical Systems · Mathematics 2011-12-21 Ken Dykema , David Kerr , Mikael Pichot

In terms of the best approximations of functions and generalized moduli of smoothness, direct and inverse approximation theorems are proved for Besicovitch almost periodic functions whose Fourier exponent sequences have a single limit point…

Classical Analysis and ODEs · Mathematics 2025-09-30 Stanislav Chaichenko , Andrii Shidlich , Tetiana Shulyk

We show that a non-universal Polish group can induce a complete orbit equivalence relation, which answers a question of Sabok from \cite{OPENPROBLEMS}.

Logic · Mathematics 2026-04-22 Longyun Ding , Ruiwen Li , Bo Peng

In this paper, we study dynamics of maps on quasi-graphs characterizing their invariant measures. In particular, we prove that every invariant measure of quasi-graph map with zero topological entropy has discrete spectrum. Additionally, we…

Dynamical Systems · Mathematics 2022-03-18 Jian Li , Piotr Oprocha , Guohua Zhang

We apply the theory of large-scale geometry of Polish groups to groups of absolutely continuous homeomorphisms. Let $M$ be either the compact interval or circle. We prove that the Polish group $\operatorname{AC}_+(M)$ of…

Group Theory · Mathematics 2018-03-01 Jake Herndon

In this note we consider dynamical systems $(X,G)$ on a Cantor set $X$ satisfying some mild technical conditions. The considered class includes, in particular, minimal and transitive aperiodic systems. We prove that two such systems…

Dynamical Systems · Mathematics 2014-02-26 Konstantin Medynets

In this paper, we first show that for a countable family of random elements taking values in a partially ordered Polish space (POP), association (both positive and negative) of all finite dimensional marginals implies that of the infinite…

Probability · Mathematics 2019-12-04 Guenter Last , Ryszard Szekli , D. Yogeshwaran

We give a new, two-step approach to prove existence of finite invariant measures for a given Markovian semigroup. First, we identify a convenient auxiliary measure and then we prove conditions equivalent to the existence of an invariant…

Probability · Mathematics 2016-03-15 Lucian Beznea , Iulian Cîmpean , Michael Röckner

A topological space is almost locally compact if it contains a dense locally compact subspace. We generalize a result from \cite{Ma}, showing that isomorphism on Borel classes of almost locally compact Polish metric structures is always…

Logic · Mathematics 2025-08-12 Maciej Malicki

It is proved that two useful and apparently different metrics on the set of Borel probabilities on countable products of Polish spaces of bounded diameters are equal. This paves the way for advances in their computation.

Probability · Mathematics 2021-04-20 J. Armstrong-Goodall , R. S. MacKay

We introduce the notion of an invariantly universal pair (S,E) where S is an analytic quasi-order and E \subseteq S is an analytic equivalence relation. This means that for any analytic quasi-order R there is a Borel set B invariant under E…

Logic · Mathematics 2013-02-08 Riccardo Camerlo , Alberto Marcone , Luca Motto Ros

An inner-distal homeomorphism is one such that each of its proximal cells has empty interior. In locally connected spaces, we prove these homeomorphisms have the following properties: Every $cw$-distal homeomorphism is inner-distal but not…

Dynamical Systems · Mathematics 2023-10-10 J. Aponte , D. Carrasco-Olivera , H. Villavicencio

This expository paper is intended for a short self-contained introduction to the theory of infinite convolutions of probability measures on Polish semigroups. We give the proofs of the Rees decomposition theorem of completely simple…

Probability · Mathematics 2021-08-31 Kouji Yano

For continuous maps on a compact manifold M, particularly for those that do not preserve the Lebesgue measure m, we define the observable invariant probability measures as a generalization of the physical measures. We prove that any…

Dynamical Systems · Mathematics 2012-03-01 E. Catsigeras , H. Enrich

We give a new proof of a theorem of Giordano, Putnam and Skau characterizing orbit equivalence of minimal homeomorphisms of the Cantor space in terms of their sets of invariant Borel probability measures. The proof is based on a…

Dynamical Systems · Mathematics 2023-02-21 Julien Melleray , Simon Robert

The main result of this note, Theorem 2, is the following: a Borel measure on the space of infinite Hermitian matrices, that is invariant under the action of the infinite unitary group and that admits well-defined projections onto the…

Dynamical Systems · Mathematics 2011-08-16 Alexander I. Bufetov

We prove that the homeomorphism problem for connected compact metric spaces is Borel bireducible with a universal orbit equivalence relation induced by a Borel action of a Polish group.

Logic · Mathematics 2016-04-13 Cheng Chang , Su Gao

In a recent paper (2018), D. Hofmann, R. Neves and P. Nora proved that the dual of the category of compact partially ordered spaces and monotone continuous maps is a quasi-variety - not finitary, but bounded by $\aleph_1$. An open question…

Logic · Mathematics 2022-11-09 Marco Abbadini

We show that, on any given finite Borel measure space with the ambient space being a Polish metric space, every Borel real-valued function is almost a bounded, uniformly continuous function in the sense that for every $\varepsilon > 0$…

Functional Analysis · Mathematics 2020-08-04 Yu-Lin Chou