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We show that ergodic flows in noncommutative fully symmetric spaces (associated with a semifinite von Neumann algebra) generated by continuous semigroups of positive Dunford-Schwartz operators and modulated by bounded Besicovitch almost…

Operator Algebras · Mathematics 2018-09-07 Vladimir Chilin , Semyon Litvinov

Let $u_1,\ldots,u_n$ be unitary operators on a Hilbert space $H$. We study the norm $$\left\|\sum^{i=n}_{i=1} u_i \otimes \bar u_i\right\|\leqno (1)$$ of the operator $\sum u_i \otimes \bar u_i$ acting on the Hilbertian tensor product…

Functional Analysis · Mathematics 2009-09-25 Gilles Pisier

We initiate the study of effective pointwise ergodic theorems in resource-bounded settings. Classically, the convergence of the ergodic averages for integrable functions can be arbitrarily slow. In contrast, we show that for a class of…

Computational Complexity · Computer Science 2021-02-16 Satyadev Nandakumar , Subin Pulari

We prove pointwise convergence, as $N\to \infty$, for the multiple ergodic averages $\frac{1}{N}\sum_{n=1}^N f(T^nx)\cdot g(S^{a_n}x)$, where $T$ and $S$ are commuting measure preserving transformations, and $a_n$ is a random version of the…

Dynamical Systems · Mathematics 2011-04-19 Nikos Frantzikinakis , Emmanuel Lesigne , Mate Wierdl

This brief pedagogical note re-proves a simple theorem on the convergence, in $L_2$ and in probability, of time averages of non-stationary time series to the mean of expectation values. The basic condition is that the sum of covariances…

Probability · Mathematics 2022-03-22 Cosma Rohilla Shalizi

We introduce a new class of sparse sequences that are ergodic and pointwise universally $L^2$-good for ergodic averages. That is, sequences along which the ergodic averages converge almost surely to the projection to invariant functions.…

Dynamical Systems · Mathematics 2025-08-27 Sebastián Donoso , Alejandro Maass , Vicente Saavedra-Araya

In this article, we study the bilaterally almost uniform (b.a.u.) convergence of weighted averages of a positive Dunford-Schwartz operator on the noncommutative $L_p$-spaces associated to a semifinite von Neumann algebra by a large number…

Operator Algebras · Mathematics 2026-04-30 Morgan O'Brien

The mean ergodic theorem is equivalent to the assertion that for every function K and every epsilon, there is an n with the property that the ergodic averages A_m f are stable to within epsilon on the interval [n,K(n)]. We show that even…

Dynamical Systems · Mathematics 2016-07-15 Jeremy Avigad , Philipp Gerhardy , Henry Towsner

For an ergodic action of the group $Z^n$ on a probability space and a given arbitrarily slowly decreasing to zero sequence, there exists an integrable function such that the standard ergodic time averages for it converge almost everywhere…

Dynamical Systems · Mathematics 2025-08-04 Valery V. Ryzhikov

Let $X$ be a locally compact Hausdorff space with $n$ proper continuous self maps $\tau_i:X \to X$ for $1 \le i \le n$. To this we associate two topological conjugacy algebras which emerge as the natural candidates for the universal algebra…

Operator Algebras · Mathematics 2011-11-09 Kenneth R. Davidson , Elias G. Katsoulis

The Birkhoff Ergodic Theorem concludes that time averages, i.e., Birkhoff averages, $\Sigma_{n=0}^{N-1} f(x_n)/N$ of a function $f$ along a length $N$ ergodic trajectory $(x_n)$ of a function $T$ converge to the space average $\int f d\mu$,…

Dynamical Systems · Mathematics 2018-01-31 Suddhasattwa Das , Yoshitaka Saiki , Evelyn Sander , James A Yorke

We show that for the generic sequence (a) of elements in a subset A of a separable locally convex metrisable space V, the sequences [T^k(a)]_n, n=1,2,... are dense in the convex hull convA of A for all k=1,2,...; where T is the Cesaro…

Functional Analysis · Mathematics 2012-11-06 Theodosios Douvropoulos

In this paper, for a discontinuous skew-product transformation with the integrable observation function, we obtain uniform ergodic theorem and semi-uniform ergodic theorem. The main assumptions are that discontinuity sets of transformation…

Dynamical Systems · Mathematics 2017-11-07 Xia Pan , Zuohuan Zheng , Zhe Zhou

The main purpose of this paper is to prove the mean ergodic theorem for nonexpansive mappings and semigroups in locally compact Hadamard spaces, including finite dimensional Hadamard manifolds. The main tool for proving ergodic convergence…

Functional Analysis · Mathematics 2021-05-07 Hadi Khatibzadeh , Hadi Pouladi

We prove a new weak mean ergodic theorem (Theorem A) for 1-cocycles associated to weakly mixing representations of amenable groups. Let $G$ be a finitely generated, discrete, amenable group $G$ which admits a controlled Folner sequence. We…

Group Theory · Mathematics 2012-08-06 Ionut Chifan , Thomas Sinclair

We establish results with an arithmetic flavor that generalize the polynomial multidimensional Szemeredi theorem and related multiple recurrence and convergence results in ergodic theory. For instance, we show that in all these statements…

Dynamical Systems · Mathematics 2015-11-19 Nikos Frantzikinakis , Bernard Host

In this paper, we study (uniformly) mean ergodic composition operators on $H^\infty(\mathbb{B}_n)$. Under some additional assumptions, it is shown that mean ergodic operators have norm convergent iterates in $H^\infty(\mathbb{B}_n)$, and…

Functional Analysis · Mathematics 2022-03-15 Hamzeh Keshavarzi

The almost sure convergence of ergodic averages in Birkhoff's pointwise ergodic theorem is known to fail in the finitely additive setting. We introduce a natural reformulation of almost sure convergence suitable for finitely additive…

Dynamical Systems · Mathematics 2025-11-05 Morenikeji Neri

Based on T.Tao's result of norm convergence of multiple ergodic averages for commut-ing transformation, we obtain there is a subsequence which converges almost everywhere. Meanwhile, the ergodic behaviour, which the time average is equal to…

Dynamical Systems · Mathematics 2021-12-07 Xia Pan , Zuohuan Zheng , Zhe Zhou

We consider when there is absolute or unconditional convergence of series of various types of stochastic processes. These processes include differences of averages in ergodic theory and harmonic analysis, like the classical Cesaro average…

Dynamical Systems · Mathematics 2025-01-17 Bryan Johnson , Joseph Rosenblatt