On lower bounded orbits of the times-q map

TL;DR

This paper investigates the Hausdorff dimension of certain non-dense orbits of the times-q map on the unit interval, providing spectral radius calculations and asymptotic behavior as q increases.

Contribution

It characterizes the characteristic polynomials of transition matrices for these orbits and analyzes the spectral radius, offering new asymptotic insights as q approaches infinity.

Findings

Spectral radius of transition matrices explicitly characterized.

Hausdorff dimension map is continuous and constant almost everywhere.

Asymptotic behavior of the dimension map as q tends to infinity analyzed.

Abstract

In this paper we consider the times-q map on the unit interval as a subshift of finite type by identifying each number with its base q expansion, and we study certain non-dense orbits of this system where no element of the orbit is smaller than some fixed parameter c. The Hausdorff dimension of these orbits can be calculated using the spectral radius of the transition matrix of the corresponding subshift, and using simple methods based on Euclidean division in the integers, we completely characterize the characteristic polynomials of these matrices as well as give the value of the spectral radius for certain values of c. It is known through work of Urbanski and Nilsson that the Hausdorff dimension of the orbits men- tioned above as a map of c is continuous and constant almost everywhere, and as a new result we give some asymptotic results on how this map behaves as q goes to infinity,