A particular universal cellular automaton

Abstract. Signals are a classical tool of cellular automata construc-tions that proved to be useful for language recognition or firing-squad synchronisation. Particles and collisions formalize this idea one step fur-ther, describing regular nets of colliding signals. In the present paper, we investigate the use of particles and collisions for constructions involving an infinite number of interacting particles. We obtain a high-level con-struction for a new smallest intrinsically universal cellular automaton with 4 states