English

A strong Borel--Cantelli lemma for recurrence

Dynamical Systems 2024-05-07 v2

Abstract

Consider a mixing dynamical systems ([0,1],T,μ)([0,1], T, \mu), for instance a piecewise expanding interval map with a Gibbs measure μ\mu. Given a non-summable sequence (mk)(m_k) of non-negative numbers, one may define rk(x)r_k (x) such that μ(B(x,rk(x))=mk\mu (B(x, r_k(x)) = m_k. It is proved that for almost all xx, the number of knk \leq n such that Tk(x)Bk(x)T^k (x) \in B_k (x) is approximately equal to m1++mnm_1 + \ldots + m_n. This is a sort of strong Borel--Cantelli lemma for recurrence. A consequence is that limr0logτB(x,r)(x)logμ(B(x,r))=1 \lim_{r \to 0} \frac{\log \tau_{B(x,r)} (x)}{- \log \mu (B (x,r))} = 1 for almost every xx, where τ\tau is the return time.

Keywords

Cite

@article{arxiv.2202.07344,
  title  = {A strong Borel--Cantelli lemma for recurrence},
  author = {Tomas Persson},
  journal= {arXiv preprint arXiv:2202.07344},
  year   = {2024}
}

Comments

16 pages, 0 figures. Minor corrections, in particular to the proof of Proposition 1

R2 v1 2026-06-24T09:37:48.270Z