Distribution of integers with digit restrictions via Markov chains

TL;DR

This paper introduces a Markov chain-based method to analyze the distribution of integers with digit restrictions, providing new conditions for uniform distribution in residue classes and extending previous results to more general sets.

Contribution

It presents a novel Markov chain approach to study digit-restricted integer distributions, extending uniformity results to multiplicatively invariant sets and addressing open questions.

Findings

Derived a necessary and sufficient condition for uniform distribution of missing digit sets.

Extended distribution results to a broader class of multiplicatively invariant sets.

Provided a new analytical framework avoiding Fourier analysis.

Abstract

In this paper, we introduce a new technique to study the distribution in residue classes of sets of integers with digit and sum-of-digits restrictions. From our main theorem, we derive a necessary and sufficient condition for integers with missing digits to be uniformly distributed in arithmetic progressions, extending previous results going back to the work of Erd\H{o}s, Mauduit and S\'ark\"ozy. Our approach utilizes Markov chains and does not rely on Fourier analysis as many results of this nature do. Our results apply more generally to the class of multiplicatively invariant sets of integers. This class, defined by Glasscock, Moreira and Richter using symbolic dynamics, is an integer analogue to fractal sets and includes all missing digits sets. We address uniform distribution in this setting, partially answering an open question posed by the same authors.