Higher order Birkhoff averages

TM Jordan, V Naudot, T Young

Research output: Contribution to journalArticle (Academic Journal)peer-review

7 Citations (Scopus)

Abstract

There are well-known examples of dynamical systems for which the Birkhoff averages with respect to a given observable along some or all of the orbits do not converge. It has been suggested that such orbits could be classified using higher order averages. In the case of a bounded observable, we show that a classical result of G.H. Hardy implies that if the Birkhoff averages do not converge, then neither do the higher order averages. If the Birkhoff averages do not converge then we may denote by [αk,βk] the limit set of the k-th order averages. The sequence of intervals thus generated is nested: [αk+1,βk+1]⊂[αk,βk]. We can thus make a distinction among non-convergent Birkhoff averages; either: B1. [image omitted] is a point B∞, or, B2. [image omitted] is an interval [α∞,β∞]. We give characterizations of the types B1 and B2 in terms of how slowly they oscillate and we give examples that exhibit both behaviours B1 and B2 in the context of full shifts on finite symbols and 'Bowen's example'. For finite full shifts, we show that the set of orbits with type B2 behaviour has full topological entropy.
Translated title of the contributionHigher order Birkhoff averages
Original languageEnglish
Pages (from-to)299 - 313
Number of pages15
JournalDynamical Systems
Volume24, issue 3
DOIs
Publication statusPublished - Sep 2009

Bibliographical note

Publisher: Taylor & Francis Ltd

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