scholarly journals Sofic entropy of Gaussian actions

2016 ◽  
Vol 37 (7) ◽  
pp. 2187-2222 ◽  
Author(s):  
BEN HAYES
Keyword(s):  
Probability Measure ◽  
Fourier Analysis ◽  
Harmonic Analysis ◽  
Discrete Group ◽  
Orthogonal Representation ◽  
Countable Discrete Group ◽  
Abelian Case ◽  
Sofic Entropy ◽  
Model Formalism ◽  
Invent Math

Associated to any orthogonal representation of a countable discrete group, is a probability measure-preserving action called the Gaussian action. Using the Polish model formalism we developed before, we compute the entropy (in the sense of Bowen [J. Amer. Math. Soc.23(2010) 217–245], Kerr and Li [Invent. Math.186(2011) 501–558]) of Gaussian actions when the group is sofic. Computation of entropy for Gaussian actions has only been done when the acting group is abelian and thus our results are new, even in the amenable case. Fundamental to our approach are methods of non-commutative harmonic analysis and$C^{\ast }$-algebras which replace the Fourier analysis used in the abelian case.

scholarly journals Krieger’s finite generator theorem for actions of countable groups III

2020 ◽  
pp. 1-37 ◽  
Author(s):  
ANDREI ALPEEV ◽  
BRANDON SEWARD
Keyword(s):  
Probability Measure ◽  
Inverse Limits ◽  
Finite Generator ◽  
Generator Theorem ◽  
Sofic Entropy ◽  
The Relationship ◽  
Invent Math

Abstract We continue the study of Rokhlin entropy, an isomorphism invariant for probability-measure-preserving (p.m.p.) actions of countablegroups introduced in Part I [B. Seward. Krieger’s finite generator theorem for actions of countable groups I. Invent. Math. 215(1) (2019), 265–310]. In this paper we prove a non-ergodic finite generator theorem and use it to establish sub-additivity and semicontinuity properties of Rokhlin entropy. We also obtain formulas for Rokhlin entropy in terms of ergodic decompositions and inverse limits. Finally, we clarify the relationship between Rokhlin entropy, sofic entropy, and classical Kolmogorov–Sinai entropy. In particular, using Rokhlin entropy we give a new proof of the fact that ergodic actions with positive sofic entropy have finite stabilizers.

scholarly journals Joseph Fourier 250thBirthday: Modern Fourier Analysis and Fourier Heat Equation in Information Sciences for the XXIst Century

Entropy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 250
Author(s):  
Frédéric Barbaresco ◽  
Jean-Pierre Gazeau
Keyword(s):  
Fourier Analysis ◽  
Heat Equation ◽  
Harmonic Analysis ◽  
Lie Groups ◽  
Coherent States ◽  
Geometric Theory ◽  
Plancherel Formula ◽  
Group Representations ◽  
Modern Development ◽  
Xxist Century

For the 250th birthday of Joseph Fourier, born in 1768 at Auxerre in France, this MDPI special issue will explore modern topics related to Fourier analysis and Fourier Heat Equation. Fourier analysis, named after Joseph Fourier, addresses classically commutative harmonic analysis. The modern development of Fourier analysis during XXth century has explored the generalization of Fourier and Fourier-Plancherel formula for non-commutative harmonic analysis, applied to locally compact non-Abelian groups. In parallel, the theory of coherent states and wavelets has been generalized over Lie groups (by associating coherent states to group representations that are square integrable over a homogeneous space). The name of Joseph Fourier is also inseparable from the study of mathematics of heat. Modern research on Heat equation explores geometric extension of classical diffusion equation on Riemannian, sub-Riemannian manifolds, and Lie groups. The heat equation for a general volume form that not necessarily coincides with the Riemannian one is useful in sub-Riemannian geometry, where a canonical volume only exists in certain cases. A new geometric theory of heat is emerging by applying geometric mechanics tools extended for statistical mechanics, for example, the Lie groups thermodynamics.

scholarly journals Functional Equations and Fourier Analysis

2013 ◽  
Vol 56 (1) ◽  
pp. 218-224 ◽  
Author(s):  
Dilian Yang
Keyword(s):  
Representation Theory ◽  
Fourier Analysis ◽  
Harmonic Analysis ◽  
Functional Equations ◽  
Compact Groups ◽  
Wilson Equation ◽  
D’Alembert Equation

AbstractBy exploring the relations among functional equations, harmonic analysis and representation theory, we give a unified and very accessible approach to solve three important functional equations- the d'Alembert equation, the Wilson equation, and the d'Alembert long equation-on compact groups.

Invariant measures for interval maps with different one-sided critical orders

2013 ◽  
Vol 35 (3) ◽  
pp. 835-853 ◽  
Author(s):  
HONGFEI CUI ◽  
YIMING DING
Keyword(s):  
Probability Measure ◽  
Critical Points ◽  
Mild Condition ◽  
Invariant Measures ◽  
Invariant Probability Measure ◽  
Absolutely Continuous ◽  
Interval Maps ◽  
Jump Discontinuities ◽  
Point Set ◽  
Invent Math

AbstractFor an interval map whose critical point set may contain critical points with different one-sided critical orders and jump discontinuities, under a mild condition on critical orbits, we prove that it has an invariant probability measure which is absolutely continuous with respect to Lebesgue measure by using the methods of Bruin et al [Invent. Math. 172(3) (2008), 509–533], together with ideas from Nowicki and van Strien [Invent. Math. 105(1) (1991), 123–136]. We also show that it admits no wandering intervals.

scholarly journals An Abramov formula for stationary spaces of discrete groups

2013 ◽  
Vol 34 (3) ◽  
pp. 837-853 ◽  
Author(s):  
YAIR HARTMAN ◽  
YURI LIMA ◽  
OMER TAMUZ
Keyword(s):  
Random Walk ◽  
Probability Measure ◽  
Finite Index ◽  
Discrete Group ◽  
Return Time ◽  
Discrete Groups ◽  
Poisson Boundary ◽  
Index Subgroup ◽  
Expected Return ◽  
Finite Index Subgroup

AbstractLet $(G, \mu )$ be a discrete group equipped with a generating probability measure, and let $\Gamma $ be a finite index subgroup of $G$. A $\mu $-random walk on $G$, starting from the identity, returns to $\Gamma $ with probability one. Let $\theta $ be the hitting measure, or the distribution of the position in which the random walk first hits $\Gamma $. We prove that the Furstenberg entropy of a $(G, \mu )$-stationary space, with respect to the action of $(\Gamma , \theta )$, is equal to the Furstenberg entropy with respect to the action of $(G, \mu )$, times the index of $\Gamma $ in $G$. The index is shown to be equal to the expected return time to $\Gamma $. As a corollary, when applied to the Furstenberg–Poisson boundary of $(G, \mu )$, we prove that the random walk entropy of $(\Gamma , \theta )$ is equal to the random walk entropy of $(G, \mu )$, times the index of $\Gamma $ in $G$.

scholarly journals Amenable actions of discrete groups

1993 ◽  
Vol 13 (2) ◽  
pp. 289-318 ◽  
Author(s):  
G. A. Elliott ◽  
T. Giordano
Keyword(s):  
Discrete Group ◽  
Structure Theorem ◽  
Discrete Groups ◽  
Countable Discrete Group

AbstractA structure theorem is established for amenable actions of a countable discrete group.

scholarly journals Dynamical complexity and K-theory of Lp operator crossed products

2019 ◽  
pp. 1-33
Author(s):  
Yeong Chyuan Chung
Keyword(s):  
Compact Hausdorff Space ◽  
Discrete Group ◽  
Hausdorff Space ◽  
Crossed Products ◽  
Dynamical Complexity ◽  
Countable Discrete Group ◽  
K Theory ◽  
Assembly Map

We apply quantitative (or controlled) [Formula: see text]-theory to prove that a certain [Formula: see text] assembly map is an isomorphism for [Formula: see text] when an action of a countable discrete group [Formula: see text] on a compact Hausdorff space [Formula: see text] has finite dynamical complexity. When [Formula: see text], this is a model for the Baum–Connes assembly map for [Formula: see text] with coefficients in [Formula: see text], and was shown to be an isomorphism by Guentner et al.

scholarly journals SOME BASIC RESULTS FOR PROPER FREE G-MANIFOLDS, WHERE G IS A DISCRETE GROUP

2002 ◽  
Vol 45 (1) ◽  
pp. 43-48
Author(s):  
Marja Kankaanrinta
Keyword(s):  
Discrete Group ◽  
Dense Subset ◽  
Subject Classification ◽  
Open Dense Subset ◽  
Equivariant Maps ◽  
Countable Discrete Group ◽  
Transversality Theorem ◽  
Equivariant Version

AbstractLet $G$ be a countable discrete group and let $M$ be a proper free $C^r$ $G$-manifold and $N$ a $C^r$ $G$-manifold, where $1\leq r\leq\omega$. We prove that if $G$ acts properly and freely also on $N$ and if $\dim(N)\geq2\dim(M)$, then equivariant immersions form an open dense subset in the space $C^r_G(M,N)$ of all equivariant $C^r$ maps from $M$ to $N$. The space $C^r_G(M,N)$ is equipped with a topology, which coincides with the Whitney $C^r$ topology if $G$ is finite and is suited to studying equivariant maps. We also prove an equivariant version of Thom’s transversality theorem and show that $C^\omega_G(M,N)$ is dense in $C^r_G(M,N)$, for $1\leq r\leq\infty$.AMS 2000 Mathematics subject classification: Primary 57S20

BOUNDED COCYCLES ON FINITE VON NEUMANN ALGEBRAS

2001 ◽  
Vol 12 (06) ◽  
pp. 743-750 ◽  
Author(s):  
TERESA BATES ◽  
THIERRY GIORDANO
Keyword(s):  
Discrete Group ◽  
Von Neumann Algebra ◽  
Von Neumann Algebras ◽  
Von Neumann ◽  
Countable Discrete Group ◽  
Finite Von Neumann Algebra ◽  
Finite Von Neumann Algebras ◽  
Uniformly Bounded

In this note we prove that if G is a countable discrete group, then every uniformly bounded cocycle from a standard Borel G-space into a finite Von Neumann algebra is cohomologous to a unitary cocycle. This generalizes results of both F. H. Vasilescu and L. Zsidó and R. J. Zimmer.

Countable Amenable Identity Excluding Groups

2004 ◽  
Vol 47 (2) ◽  
pp. 215-228 ◽  
Author(s):  
Wojciech Jaworski
Keyword(s):  
Probability Measure ◽  
Unitary Representation ◽  
Discrete Group ◽  
Polynomial Growth ◽  
Irreducible Unitary Representation ◽  
Compact Groups ◽  
Groups Of Polynomial Growth ◽  
Identity Representation ◽  
Dimensional Identity

AbstractA discrete group G is called identity excluding if the only irreducible unitary representation of G which weakly contains the 1-dimensional identity representation is the 1-dimensional identity representation itself. Given a unitary representation π of G and a probability measure μ on G, let Pμ denote the μ-average ∫π(g)μ(dg). The goal of this article is twofold: (1) to study the asymptotic behaviour of the powers , and (2) to provide a characterization of countable amenable identity excluding groups. We prove that for every adapted probability measure μ on an identity excluding group and every unitary representation π there exists and orthogonal projection Eμ onto a π-invariant subspace such that for every a ∈ supp μ. This also remains true for suitably defined identity excluding locally compact groups. We show that the class of countable amenable identity excluding groups coincides with the class of FC-hypercentral groups; in the finitely generated case this is precisely the class of groups of polynomial growth. We also establish that every adapted random walk on a countable amenable identity excluding group is ergodic.

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