We study the strong Borel-Cantelli property both for events and for shifts on sequence spaces considering both a conventional and a nonconventional setups. Namely, under certain conditions on events $Γ_1,Γ_2,...$ we show that with probability one \[ \left(\sum_{n=1}^N\prod_{i=1}^\ell P(Γ_{q_i(n)})\right)^{-1}\sum_{n=1}^N\prod_{i=1}^\ell\mathbb{I}_{Γ_{q_i(n)}}\to 1\,\,\mbox{as}\,\, N\to\infty \] where $q_i(n),\, i=1,...,\ell$ are integer valued functions satisfying certain assumptions and $\mathbb{I}_Γ$ denotes the indicator of $Γ$. When $\ell=1$ (called the conventional setup) this convergence can be established under $ϕ$-mixing conditions while when $\ell>1$ (called a nonconventional setup) the stronger $ψ$-mixing condition is required. These results are extended to shifts $T$ of sequence spaces where $Γ_{q_i(n)}$ is replaced by $T^{-q_i(n)}C_n^{(i)}$ where $C_n^{(i)},\, i=1,...,\ell,\, n\geq 1$ is a sequence of cylinder sets. As an application we study the asymptotical behavior of maximums of certain logarithmic distance functions and of (multiple) hitting times of shrinking cylinders.
Criteria for Borel-Cantelli lemmas with applications to Markov chains and dynamical systems
设(Xk)是一个严格平稳的随机变量序列,其值在某个Polish空间E中,且有公共边缘$μ$,(Ak)k>0是E中的Borel集序列.本文给出了事件{Xk $\in$ Ak}满足Borel-Cantelli(或强Borel-Cantelli)性质的关于(Xk)和(Ak)的一些条件.特别地,我们证明了,如果$μ$(lim sup n A n)> 0,Borel-Cantelli性质对任何绝对正则序列都成立.在A-k是嵌套的情况下,我们在一些例子中表明,需要混合系数的收敛速率。最后,我们给出了这些结果的扩展到较弱的概念的依赖,产生的应用程序,非不可约马尔可夫链和动力系统。