Reversibility of Linear Cellular Automata on Cayley Trees with Periodic Boundary Condition

TL;DR

This paper investigates the reversibility of linear cellular automata on Cayley trees with periodic boundary conditions, providing explicit criteria and a potential approach for a generally undecidable problem.

Contribution

It offers explicit formulas and criteria for reversibility of linear cellular automata on Cayley trees, advancing understanding of an otherwise undecidable problem.

Findings

Derived explicit reversibility criteria for specific cases

Provided formulas for automata over  and 

Suggested a new approach for a generally undecidable problem

Abstract

While one-dimensional cellular automata have been well studied, there are relatively few results about multidimensional cellular automata; the investigation of cellular automata defined on Cayley trees constitutes an intermediate class. This paper studies the reversibility of linear cellular automata defined on Cayley trees with periodic boundary condition, where the local rule is given by $f(x_0, x_1, \ldots, x_d) = b x_0 + c_1 x_1 + \cdots + c_d x_d \pmod{m}$ for some integers $m, d \geq 2$. The reversibility problem relates to solving a polynomial derived from a recurrence relation, and an explicit formula is revealed; as an example, the complete criteria of the reversibility of linear cellular automata defined on Cayley trees over $\mathbb{Z}_2$, $\mathbb{Z}_3$, and some other specific case are addressed. Further, this study achieves a possible approach for determining the reversibility of multidimensional cellular automata, which is known as a undecidable problem.