Recurrence of Stationary Sequences
Geman, Donald ; Horowitz, Joseph ; Zinn, Joel
Ann. Probab., Tome 4 (1976) no. 6, p. 372-381 / Harvested from Project Euclid
Let $\{X_n\}^{+\infty}_{-\infty}$ be a stationary sequence of random variables, with common distribution $\pi(dx)$. If the initial value $X_0$ is repeated with probability one (e.g. when $\pi(dx)$ is discrete), then the "shifted" sequence $\{X_{n+N}\}^\infty_{-\infty}$ is also stationary where $N = N(\omega)$ is the first $n > 0$ for which $X_n(\omega) = X_0(\omega)$. Surprisingly, this may even occur when $\pi(dx)$ is continuous and $\{X_n\}$ is ergodic (although not when $\{X_n\}$ is $\phi$-mixing). For Markov sequences, we also give other conditions which prohibit the a.s. recurrence of $X_0$. For recurrent sequences, we show that when $X_0$ is "conditionally discrete," the invariant $\sigma$-field for the $\{X_{n+N}\}$ process coincides (up to null sets) with $X_0 \vee \mathscr{A}$, the $\sigma$-field generated by $X_0$ and the invariant sets for $\{X_n\}$. Finally, we find an expression for $E(N\mid X_0 \vee \mathscr{A})$ which reduces to Kac's recurrence formula when $X_0$ is an indicator function.
Publié le : 1976-06-14
Classification:  Stationary sequence,  recurrence,  flow,  $\phi$-mixing,  invariant set,  60G10,  28A65
@article{1176996086,
     author = {Geman, Donald and Horowitz, Joseph and Zinn, Joel},
     title = {Recurrence of Stationary Sequences},
     journal = {Ann. Probab.},
     volume = {4},
     number = {6},
     year = {1976},
     pages = { 372-381},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1176996086}
}
Geman, Donald; Horowitz, Joseph; Zinn, Joel. Recurrence of Stationary Sequences. Ann. Probab., Tome 4 (1976) no. 6, pp.  372-381. http://gdmltest.u-ga.fr/item/1176996086/