Frog model on $\mathbb{Z}$ with random survival parameter

Abstract

We study the frog model on \( \mathbb{Z} \) with geometric lifetimes, introducing a random survival parameter. Active and inactive particles are placed at the vertices of \( \mathbb{Z} \). The lifetime of each active particle follows a geometric random variable with parameter \( 1-p \), where \( p \) is randomly sampled from a distribution \( π\). Each active particle performs a simple random walk on \( \mathbb{Z} \) until it dies, activating any inactive particles it encounters along its path. In contrast to the usual case where \( p \) is fixed, we show that there exist non-trivial distributions \( π\) for which the model survives with positive probability. More specifically, for $\ddot{I}€\sim Beta(\hat{I}\pm ,{\hat{I}}^2)$, we establish the existence of a critical value \( β=0.5 \), that separates almost sure extinction from survival with positive probability. Furthermore, we show that the model is recurrent whenever it survives with positive probability.

17 pages, 1 figure