Proof of a Phase Transition in Probabilistic Cellular Automata

Abstract

Cellular automata are a model of parallel computing. It is well known that simple deterministic cellular automata may exhibit complex behaviors such as Turing universality [3,13] but only few results are known about complex behaviors of probabilistic cellular automata.

Several studies have focused on a specific probabilistic dynamics: α-asynchronism where at each time step each cell has a probability α to be updated. Experimental studies [5] followed by mathematical analysis [2,4,7,8] have permitted to exhibit simple rules with interesting behaviors. Among these behaviors, most of these studies conjectured that some cellular automata exhibit a polynomial/exponential phase transition on their convergence time, i.e. the time to reach a stable configuration. The study of these phase transitions is crucial to understand the behaviors which appear at low synchronicity. A first analysis [14] proved the existence of the exponential phase in cellular automaton FLIP-IF-NOT-ALL-EQUAL but failed to prove the existence of the polynomial phase. In this paper, we prove the existence of a polynomial/exponential phase transition in a cellular automaton called FLIP-IF-NOT-ALL-0.