Directional Entropies of Cellular Automaton-Maps

Consider a fixed lattice L in n -dimensional euclidean space, and a finite set K of symbols. A correspondence a which assigns a symbol a(x) ∈K to each lattice point x ∈ L will be called a configuration. An n -dimensional cellular automaton can be described as a map which assigns to each such configuration a some new configuration a′ = f (a) by a formula of the form $$ a'(x) = F(a(x + {v_l}),...,\,a(x + {v_{\tau }})) $$ a’(x) = F(a(x + v 1)), ⋯, a(x + v r)), where v 1, ⋯, v r are fixed vectors in the lattice L, and where F is a fixed function of r symbols in K. I will call f the cellular automaton-map which is associated with the local map F. If the alphabet K has k elements, then the number of distinct local maps F is equal to k k′ . This is usually an enormous number, so that it is not possible to examine all of the possible F. Depending on the particular choice of F and of the v 1, such an automaton may display behavior which is simple and convergent, or chaotic and random looking, or behavior which is very complex and difficult to describe. (Compare [Wolfram].)