Notes on "Surjective Two-Neighbor Cellular Automata on Prime Alphabets"

A simpler proof that such CA are always permutive

Reading Hedlund after writing the paper, I realized that there is an easier (completely trivial) way to extract the result about permutivitity from Hedlund's 1969 paper; at the time of writing we seem to have missed Section 17. Here's a proof. Theorems below refer to that paper.

Solutions to open cases and an open question

In the paper, doing manual constructions we found the binary case difficult. But computers are way smarter than us, and indeed there exist non-closing surjective binary CA with radius 5:

Last update: 8.9.2017