English

Random walks on tori and normal numbers in self similar sets

Dynamical Systems 2022-08-03 v3 Number Theory Probability

Abstract

We study random walks on a dd-dimensional torus by affine expanding maps whose linear parts commute. Assuming an irrationality condition on their translation parts, we prove that the Haar measure is the unique stationary measure. We deduce that if KRdK \subset \mathbb{R}^d is an attractor of a finite iterated function system of n2n\geq 2 maps of the form xDrix+ti (i=1,,n)x \mapsto D^{-r_i} x + t_i \ (i=1, \ldots, n), where DD is an expanding d×dd\times d integer matrix, and is the same for all the maps, and riNr_{i} \in\mathbb{N}, under an irrationality condition on the translation parts tit_i, almost every point in KK (w.r.t. any Bernoulli measure) has an equidistributed orbit under the map xDxx\mapsto Dx (multiplication mod Zd\mathbb{Z}^{d}). In the one-dimensional case, this conclusion amounts to normality to base DD. Thus for example, almost every point in an irrational dilation of the middle-thirds Cantor set is normal to base 3.

Keywords

Cite

@article{arxiv.2002.00455,
  title  = {Random walks on tori and normal numbers in self similar sets},
  author = {Yiftach Dayan and Arijit Ganguly and Barak Weiss},
  journal= {arXiv preprint arXiv:2002.00455},
  year   = {2022}
}

Comments

The formulation of Theorem 4 was corrected. Some corrections were made in Section 5