Some sufficient conditions for cyclic trajectories in a two-dimensional analog of the 3x+1 problem

Abstract

The 3x+1 problem concerns the behavior of the iterates of the function defined by T(x) = (3x+1)/2 if x is odd, T(x) = x/2 if x is even. The 3x+1 Conjecture asserts that, starting from any positive integer alpha , repeated iteration of this function eventually produces the value 1. In this thesis we study the following extended version of the above problem. Let Z* be the set of all nonnegative integers. Let k be any fixed prime number and D=[k 0], D=[0 k] Let A be any 2x2 matrix of positive integers. For a fixed beta is an element of a set Z*2, let T: Z*2 -> Z*2 be defined by, for each alpha is an element of a set Z*2, T(alpha) = D-1 alpha if D-1 alpha is an element of a set Z*2, T(alpha) = A alpha + beta if D-1 alpha is not an element of a set Z*2. The research reported in this thesis concerns determining whether or not the trajectory [alpha, T(alpha), T2 (alpha), ...] is cyclic. For some forms of the matrix A it is proved that the trajectory cannot be cyclic for any choice of beta is an element of a set Z*2. In some other cases values of beta are given which ensure a cyclic trajectory.