Pseudoperiodicity and the $3x+1$ Conjugacy Function

Abstract

The 3x+1 function T is defined on the positive integers by $T(x) = \frac{3x+1}{2}$ for x odd and $T(x) = \frac{x}{2}$ for x even. The function T has a natural extension to the 2-adic integers, and there is a continuous function $\Phi$ which conjugates T to the 2-adic shift map $\sigma$. Bernstein and Lagarias conjectured that -1 and 1/3 are the only odd fixed points of $\Phi$. In this paper we investigate periodicity associated with $\Phi$, a property of the map which is a natural extention of solenoidality. We use it to show that there are nontrivial infinite families of 2-adics that are not fixed points of $\Phi$. In particular, we prove that three sequences of farPoints of 2-adic integers are finitely pseudoperiodic, providing more evidence supporting the $\Phi$ Fixed Point Conjecture.