Can the Ising critical behaviour survive in non-equilibrium synchronous cellular automata?

Universality classes of Ising-like phase transitions are investigated in a series of two-dimensional synchronously updated probabilistic cellular automata (PCAs), whose time evolution rules are either of Glauber type or of majority-vote type, and degrees of anisotropy are varied. Although early works showed that coupled map lattices and PCAs with synchronously updating rules belong to a universality class distinct from the Ising class, careful calculations reveal that synchronous Glauber PCAs should be categorized into the Ising class, regardless of the degree of anisotropy. Majority-vote PCAs for the system size considered yield exponents ν which are between those of the two classes, closer to the Ising value, with slight dependence on the anisotropy. The results indicate that Ising critical behaviour is robust with respect to anisotropy and synchronism for those types of non-equilibrium PCAs, and conclusions made in earlier studies on them should be reconsidered.