Volume 2
Summer 2007
Number 1

Algebraic Dynamics of a One-Parameter Class

of Maps over $\Bbb Z_2$

Luba Lidman and Diana M. Thomas

Abstract: Motivated by the Ducci Map and Wolfram's Rule 90, this paper studies the relationship of the period lengths of the maps $W(n,k)=I_n+T_n^k$ as a function of $n$ and $k$, where $I_n$ is the identity map and $T_n$ is the left shift map on $\Bbb Z_2^n$. It is found that $W(n,k)$ is conjugate to $W(n,1)$ for $(n,k)=1$. A closed form expression for the minimal polynomial of $W(n,k)$ is obtained. In addition, using the language of minimal polynomials, we find that when $(n,k) \ne 1$,the period lengths of $W(n,k)$ are equal to the period lengths of $W(s,1)$ where $s\cdot(n,k) =n$.