The constraint of a fixed spatial periodicity on a cellular automaton produces an assortment of time periods, into one of which the evolution must eventually fall. The converse problem would be to select a time interval, with the intention of enumerating the lengths of all the possible rings whose evolution would regenerate after the given delay.

- Characteristics of cycles
- Overlapping of neighborhoods
- The de Bruijn matrix
- Periods and other properties
- Superluminal configurations for Rule 22
- Periods for Rule 22
- The gap theorems

E-mail:mcintosh@servidor.unam.mx