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We show that the Poisson boundary of random walks of finite entropy on Zariski-dense discrete subgroups of semisimple Lie groups equals the Furstenberg boundary of the corresponding symmetric spaces equipped with the hitting measure,…

Dynamical Systems · Mathematics 2025-10-29 Kunal Chawla , Behrang Forghani , Joshua Frisch , Giulio Tiozzo

We study random walk on topological full groups of subshifts, and show the existence of infinite, finitely generated, simple groups with the Liouville property. Results by Matui and Juschenko-Monod have shown that the derived subgroups of…

Group Theory · Mathematics 2014-05-26 Nicolás Matte Bon

We introduce a notion of shadowing property for actions of finitely generated groups and study its basic properties. We formulate and prove a shadowing lemma for actions of nilpotent groups. We construct an example of a faithful linear…

Dynamical Systems · Mathematics 2013-09-27 Alexey Osipov , Sergey Tikhomirov

We introduce and study the notions of boundary actions and of the Furstenberg boundary of a discrete quantum group. As for classical groups, properties of boundary actions turn out to encode significant properties of the operator algebras…

Operator Algebras · Mathematics 2022-06-22 Mehrdad Kalantar , Paweł Kasprzak , Adam Skalski , Roland Vergnioux

In this paper, a polynomial version of Furstenberg joining is introduced and its structure is investigated. Particularly, it is shown that if all polynomials are non-linear, then almost every ergodic component of the joining is a direct…

Dynamical Systems · Mathematics 2023-01-20 Wen Huang , Song Shao , Xiangdong Ye

We define the Furstenberg boundary of a locally compact Hausdorff \'etale groupoid, generalising the Furstenberg boundary for discrete groups, by providing a construction of a groupoid-equivariant injective envelope. Using this injective…

Operator Algebras · Mathematics 2020-01-31 Clemens Borys

In this paper we provide a concrete construction of Furstenberg entropy values of $\tau$-boundaries of the group $\mathbb{Z}[\frac{1}{p_1},\ldots,\frac{1}{p_{l}}]\rtimes \{p_1^{n_1}\cdots p_{l}^{n_{l}} \, : \, n_i\in\mathbb{Z}\}$ by…

Dynamical Systems · Mathematics 2021-04-22 Hanna Oppelmayer

We prove that for a measure preserving action of a sofic group with positive sofic entropy, the set of points with finite stabilizer have positive measure. This extends results of Weiss and Seward for amenable groups and free groups,…

Dynamical Systems · Mathematics 2016-08-24 Tom Meyerovitch

In this paper, we study several finite approximation properties of topological full groups of group actions on the Cantor set such that free points are dense. Firstly, we establish that for such a distal action $\alpha$ of a countable…

Dynamical Systems · Mathematics 2024-03-07 Xin Ma

We prove structural results for measure preserving systems, called Furstenberg systems, naturally associated with bounded multiplicative functions. We show that for all pretentious multiplicative functions these systems always have rational…

Number Theory · Mathematics 2025-08-13 Nikos Frantzikinakis , Mariusz Lemańczyk , Thierry de la Rue

Various lower bounds are established for the entropy of sums, products and their combinations. First, we derive a prime-field analogue of a version of the entropy power inequality established by Tao over torsion-free groups. Next, we prove…

Combinatorics · Mathematics 2026-04-30 Lampros Gavalakis , Marcel K. Goh , Ioannis Kontoyiannis

We study a notion of entropy for probability measure preserving actions of finitely generated free groups, called f-invariant entropy, introduced by Lewis Bowen. In the degenerate case, the f-invariant entropy is negative infinity. In this…

Dynamical Systems · Mathematics 2015-01-15 Brandon Seward

Let $G$ be a real linear semisimple algebraic group without compact factors and $\Gamma$ a Zariski dense subgroup of $G$. In this paper, we use a probabilistic counting in order to study the asymptotic properties of $\Gamma$ acting on the…

Group Theory · Mathematics 2017-07-12 Richard Aoun

Let $G$ be a countable group and $\mu$ a probability measure on $G$. We build a new framework to compute asymptotic quantities associated with the $\mu$-random walk on $G$, using methods from harmonic analysis on groups and Banach space…

Dynamical Systems · Mathematics 2026-03-24 Benjamin Anderson-Sackaney , Tim de Laat , Ebrahim Samei , Matthew Wiersma

For the general class of quasifree fermionic right mover/left mover systems over the infinitely extended two-sided discrete line introduced in [8] within the algebraic framework of quantum statistical mechanics, we study the von Neumann…

Mathematical Physics · Physics 2025-05-27 Walter H. Aschbacher

We study an invariant of dynamical systems called naive entropy, which is defined for both measurable and topological actions of any countable group. We focus on nonamenable groups, in which case the invariant is two-valued, with every…

Dynamical Systems · Mathematics 2016-02-23 Peter Burton

We show that, for countable sofic groups, a Bernoulli action with infinite entropy base has infinite entropy with respect to every sofic approximation sequence. This builds on the work of Lewis Bowen in the case of finite entropy base and…

Dynamical Systems · Mathematics 2010-05-28 David Kerr , Hanfeng Li

In this article we prove that the set of torsion-free groups acting by isometries on a hyperbolic metric space whose entropy is bounded above and with a compact quotient is finite. The number of such groups can be estimated in terms of the…

Group Theory · Mathematics 2021-11-09 Gérard Besson , Gilles Courtois , Sylvestre Gallot , Andrea Sambusetti

We give a criterion for a set of $n$ hyperbolic isometries of a $\mathrm{CAT}(0)$ metric space $X$ to generate a free group on $n$ generators. This extends a result by Alperin, Farb and Noskov who proved this for 2 generators under the…

Group Theory · Mathematics 2022-01-25 Matthew J. Conder , Jeroen Schillewaert

Given a tracial von Neumann algebra $(M,\tau)$, we prove that a state preserving $M$-bimodular ucp map between two stationary W$^*$-extensions of $(M,\tau)$ preserves the Furstenberg entropy if and only if it induces an isomorphism between…

Operator Algebras · Mathematics 2025-03-06 Shuoxing Zhou