Dissipation, anisotropy, and the stabilization of computationally complex states of homogeneous media

The unbounded complexity exhibited by homogeneous media such as cellular automata is ordinarily quite unstable with respect to noise, with an arbitrarily small generic probabilistic perturbation causing the medium instead to relax to a unique, finitely complicated state independent of the initial conditions. We survey recent results on how irreversibility and spatial anisotropy allow unboundedly complex behavior to persist in spite of such noise. © 1990.