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We study fluctuations of ergodic averages generated by actions of amenable groups. In the setting of an abstract ergodic theorem for locally compact second countable amenable groups acting on uniformly convex Banach spaces, we deduce a…

Dynamical Systems · Mathematics 2019-01-25 Andrew Warren

By combining R{\o}rdam's construction and the author's previous construction, we provide the first examples of amenable actions of non-amenable groups on simple separable nuclear C*-algebras that are neither stably finite nor purely…

Operator Algebras · Mathematics 2025-03-03 Yuhei Suzuki

Relationships between a chaotic behavior and closely related properties of topological transitivity, sensitivity to initial conditions, density of closed orbits of homeomorphism groups and their countable products are investigated. We…

Dynamical Systems · Mathematics 2022-11-08 N. I. Zhukova , A. G. Korotkov

To answer the question whether a cascade of energy exists or not in turbulence, we propose a set of correlation functions able to test if there is an irreversible transfert of energy, step by step, from large to small structures. These…

Fluid Dynamics · Physics 2016-11-23 Christophe Josserand , Martine Le Berre , Thierry Lehner , Yves Pomeau

We study the topological dynamics of the action of an acylindrically hyperbolic group on the space of its infinite index convex cocompact subgroups by conjugation. We show that, for any suitable probability measure $\mu$, random walks with…

Group Theory · Mathematics 2025-01-10 M. Hull , A. Minasyan , D. Osin

Let G be an infinite discrete countable amenable group acting continuously on a Lebesgue space X. In this article, using partition and factor-space, the conditional entropy of the action G is defined. We introduction some properties of…

Dynamical Systems · Mathematics 2025-05-06 Yuan Lian , Bin Zhu

We characterize charmenability among arithmetic groups and deduce dichotomy statements pertaining normal subgroups, characters, dynamics, representations and associated operator algebras. We do this by studying the stationary dynamics on…

Group Theory · Mathematics 2022-08-16 Uri Bader , Itamar Vigdorovich

Let T be a free ergodic measure-preserving action of an abelian group G on (X,mu). The crossed product algebra R_T has two distinguished masas, the image C_T of L^infty(X,mu) and the algebra S_T generated by the image of G. We conjecture…

Operator Algebras · Mathematics 2007-05-23 Sergey Neshveyev , Erling Stormer

We classify measures on a homogeneous space which are invariant under a certain solvable subgroup and ergodic under its unipotent radical. Our treatment is independent of characteristic. As a result we get the first measure classification…

Dynamical Systems · Mathematics 2016-12-05 Amir Mohammadi , Alireza Salehi Golsefidy

We study actions of countable discrete groups which are amenable in the sense that there exists a mean on X which is invariant under the action of G. Assuming that G is nonamenable, we obtain structural results for the stabilizer subgroups…

Group Theory · Mathematics 2020-12-16 Robin Tucker-Drob

Suppose that $X$ is a Polish space, $E$ is a countable Borel equivalence relation on $X$, and $\mu$ is an $E$-invariant Borel probability measure on $X$. We consider the circumstances under which for every countable non-abelian free group…

Logic · Mathematics 2020-02-25 Clinton T. Conley , Benjamin D. Miller

Coherent flows of self-propelled particles are characterized by vortices and jets that sustain chaotic flows, referred to as active turbulence. Here, we reveal a crossover between defect-free active turbulence and active turbulence laden…

Soft Condensed Matter · Physics 2023-05-26 Benjamin H. Andersen , Julian Renaud , Jonas Rønning , Luiza Angheluta , Amin Doostmohammadi

We investigate compact quantum group actions on unital $C^*$-algebras by analyzing invariant subsets and invariant states. In particular, we come up with the concept of compact quantum group orbits and use it to show that countable compact…

Operator Algebras · Mathematics 2015-11-17 Huichi Huang

We use a tensor C*-category with conjugates and two quasitensor functors into the category of Hilbert spaces to define a *-algebra depending functorially on this data. If one of them is tensorial, we can complete in the maximal C*-norm. A…

Operator Algebras · Mathematics 2017-10-18 Claudia Pinzari , John E. Roberts

We investigate the representation theory of the crossed-product C*-algebra associated to a compact group G acting on a locally compact space X when the stability subgroups vary discontinuously. Our main result applies when G has a principal…

Operator Algebras · Mathematics 2015-08-27 Robert Archbold , Astrid an Huef

Given a second-countable, locally compact group $G$, we consider amenable $G$-actions on separable, stable, nuclear $\mathrm{C}^\ast$-algebras that are isometrically shift-absorbing and tensorially absorb the trivial action on the Cuntz…

Operator Algebras · Mathematics 2024-09-16 Matteo Pagliero , Gábor Szabó

We describe results from particle-in-cell simulations of driven turbulence in collisionless, magnetized, relativistic pair plasma. This physical regime provides a simple setting for investigating the basic properties of kinetic turbulence…

High Energy Astrophysical Phenomena · Physics 2018-05-23 Vladimir Zhdankin , Dmitri A. Uzdensky , Gregory R. Werner , Mitchell C. Begelman

We consider particle acceleration by large-scale incompressible turbulence with a lengthscale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended…

High Energy Astrophysical Phenomena · Physics 2015-06-12 Yutaka Ohira

We investigate the effect of cooperative interactions in an ensemble of microorganisms, modelled as self-propelled disk-like and rod-like particles, in a three-dimensional turbulent flow to show flocking as an emergent phenomenon. Building…

Soft Condensed Matter · Physics 2020-05-20 Anupam Gupta , Amal Roy , Arnab Saha , Samriddhi Sankar Ray

We investigate diffusion in supersonic, turbulent, compressible flows. Supersonic turbulence can be characterized as network of interacting shocks. We consider flows with different rms Mach numbers and where energy necessary to maintain…

Astrophysics · Physics 2009-11-07 Ralf S. Klessen , Doug N. C. Lin