Excitable medium

A group of spectators at a sporting event are an excitable medium, as can be observed in a Mexican wave (so-called from its initial appearance in the 1986 World Cup in Mexico).

Cellular automata provide a simple model to aid in the understanding of excitable media.

Each cell of the automaton is made to represent some section of the medium being modelled (for example, a patch of trees in a forest, or a segment of heart tissue).

In the forest fire example the simple rules given in Greenberg-Hastings cellular automaton[1] might be modified as follows: This function can be refined according to the particular medium.

Spiral waves constitute one of the mechanisms of fibrillation when they organize in long-lasting reentrant activities named rotors.