Rational ergodicity,bounded rational ergodicity and some continuous measures on the circle

Two ratio limit concepts for transformations preserving infinite measures, rational ergodicity and bounded rational ergodicity, are discussed and compared. The concept of rational ergodicity is used to construct some continuous measures on the circle, which show that the exceptional set in the weak mixing theorem may be rather large. To the memory of Shlomo Horowitz     

A short proof of ergodicity of Babillot-Ledrappier measures

Let be a compact manifold, and let be a transitive homologically full Anosov flow on . Let be a -cover for , and let be the lift of to . Babillot and Ledrappier exhibited a family of measures on , which are invariant and ergodic with respect to the strong stable foliation of . We provide a new short proof of ergodicity.

     

Orthogonal vector measures

This paper introduces the concept of orthogonal vector measures, and gives the Yosida-Hewittdecomposition theorem for this kind of vector measures. The major results are(a) Any orthogonal vector measure can gain it countable additivity by enlarging its domain;(b) Every orthogonal vector measure can be represented as the sum of two orthogonal vectormeasures, one of which is countably additive, and the other is purely finitely additive. Furthermore,these vector measures are completely perpendicular to each other.     

Orlicz-Sobolev inequalities for sub-Gaussian measures and ergodicity of Markov semi-groups

We study coercive inequalities in Orlicz spaces associated to the probability measures on finite- and infinite-dimensional spaces which tails decay slower than the Gaussian ones. We provide necessary and sufficient criteria for such inequalities to hold and discuss relations between various classes of inequalities.     

Irreducible recurrence,ergodicity, and extremality of invariant measures for resolvents

We analyze the transience, recurrence, and irreducibility properties of general sub-Markovian resolvents of kernels and their duals, with respect to a fixed sub-invariant measure $m$. We give a unifying characterization of the invariant functions, revealing the fact that an $L^p$-integrable function is harmonic if and only if it is harmonic with respect to the weak dual resolvent. Our approach is based on potential theoretical techniques for resolvents in weak duality. We prove the equivalence between the $m$-irreducible recurrence of the resolvent and the extremality of $m$ in the set of all invariant measures, and we apply this result to the extremality of Gibbs states. We also show that our results can be applied to non-symmetric Dirichlet forms, in general and in concrete situations. A second application is the extension of the so called Fukushima ergodic theorem for symmetric Dirichlet forms to the case of sub-Markovian resolvents of kernels.     

Necessary and sufficient conditions for Lipschitz ergodicity and generalized ergodicity

In this paper, the Lipschitz ergodicity and generalized ergodicity are studied. Some criterions for a system to be Lipschitz ergodic or generalized ergodic are given.     

Criteria on ergodicity and strong ergodicity of single death processes

Based on an explicit representation of moments of hitting times for single death processes, the criteria on ergodicity and strong ergodicity are obtained. These results can be applied for an extended class of branching processes. Meanwhile, some sufficient and necessary conditions for recurrence and exponential ergodicity as well as extinction probability for the processes are presented.     

Orthogonal harmonie analysis and scaling of fractal measures

We show that certain iteration systems lead to fractal measures admitting exact orthogonal harmonic analysis.     

Generalized ergodicity

This paper introduces generalized ergodicity which contains ergodicity and Lipschitz ergodicity, proves the equivalence relation between generalized ergodicity and chain transitivity and gives its geometrical structure     

Joint ergodicity and mixing

The study of jointly ergodic measure preserving transformations of probability spaces, begun in [1], is continued, and notions of joint weak and strong mixing are introduced. Various properties of ergodic and mixing transformations are shown to admit analogues for several transformations. The case of endomorphisms of compact abelian groups is particularly emphasized. The main result is that, given such commuting endomorphisms σ₁σ₂,...,σ, ofG, the sequence ((1/N)Σ _n=0 ^N−1 σ ₁ ⁿ f ¹·σ ₂ ⁿ f ²· ··· · σ _s ⁿ f ^sconverges inL ²(G) for everyf ₁,f ₂,…,f _s∈L ^∞(G). If, moreover, the endomorphisms are jointly ergodic, i.e., if the limit of any sequence as above is Π _i=1 ^s ∫ _G f ₁ d μ, where μ is the Haar measure, then the convergence holds also μ-a.e.     

Weak rational ergodicity does not imply rational ergodicity

We construct an uncountable family of rank-one infinite measure-preserving transformations that are weakly rationally ergodic, but are not rationally ergodic, thus answering an open question by showing that weak rational ergodicity does not imply rational ergodicity.     

Generalized ergodicity

This paper introduces generalized ergodicity which contains ergodicity and Lipschitz ergodicity, proves the equivalence relation between generalized ergodicity and chain transitivity and gives its geometrical structure     

Orthogonal polynomials and measures with finitely many point masses

Elementary proofs are given for a result of J. Geronimo and K. M. Case concerning the discrete spectrum of measures corresponding to orthogonal polynomials defined by a recerrence relation.     

Stable ergodicity and julienne quasi-conformality

In this paper we dramatically expand the domain of known stably ergodic, partially hyperbolic dynamical systems. For example, all partially hyperbolic affine diffeomorphisms of compact homogeneous spaces which have the accessibility property are stably ergodic. Our main tools are the new concepts – julienne density point and julienne quasi-conformality of the stable and unstable holonomy maps. Julienne quasi-conformal holonomy maps preserve all julienne density points. Received June 14, 1999 / final version received October 25, 1999     

Recurrence and ergodicity of diffusions

This article attempts to lay a proper foundation for studying asymptotic properties of nonhomogeneous diffusions, extends earlier criteria for transience, recurrence, and positive recurrence, and provides sufficient conditions for the weak convergence of a shifted nonhomogeneous diffusion to a limiting stationary homogenous diffusion. A functional central limit theorem is proved for the class of positive recurrent homogeneous diffusions. Upper and lower functions for positive recurrent nonhomogeneous diffusions are also studied.     

Orthogonal measures for uniform algebras of finite type

In this paper we study uniform algebras of finite type. The sufficient conditions are presented for a continuous function to belong to a maximal subalgebra of the algebra C(X).Translated from Matematicheskie Zametki, Vol. 18, No. 1, pp. 109–114, July, 1975.The author expresses his gratitude to E. A. Gorin for valuable advice and discussions.     

Quantum unique ergodicity

Consider a compact Riemannian manifold with ergodic geodesic flow. Quantum ergodicity is generalized from orthonormal bases of eigenfunctions of the Laplacian to packets of eigenfunctions. It is shown that this more general result is sharp. Namely, there may exist exceptional packets of eigenfunctions which concentrate on a submanifold.