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Periodicity and pure periodicity in alternate base systems

Zuzana Masáková, Edita Pelantová

Abstract

We study the Cantor real base numeration system which is a common generalization of two positional systems, namely the Cantor system with a sequence of integer bases and the Rényi system with one real base. We focus on the so-called alternate base $B$ given by a purely periodic sequence of real numbers greater than 1. We answer an open question of Charlier et al. on the set of numbers with eventually periodic $B$-expansions. We also investigate for which bases all sufficiently small rationals have a purely periodic $B$-expansion.

Periodicity and pure periodicity in alternate base systems

Abstract

We study the Cantor real base numeration system which is a common generalization of two positional systems, namely the Cantor system with a sequence of integer bases and the Rényi system with one real base. We focus on the so-called alternate base given by a purely periodic sequence of real numbers greater than 1. We answer an open question of Charlier et al. on the set of numbers with eventually periodic -expansions. We also investigate for which bases all sufficiently small rationals have a purely periodic -expansion.
Paper Structure (7 sections, 15 theorems, 72 equations)

This paper contains 7 sections, 15 theorems, 72 equations.

Key Result

Theorem 1

Let $\boldsymbol{\mathcal{B}}=(\beta_1,\dots,\beta_{p})$ be an alternate base and set $\delta=\prod_{i=1}^p \beta_i$.

Theorems & Definitions (30)

  • Theorem 1: CCK23
  • Theorem A
  • Theorem 2: A98
  • Theorem B
  • Theorem C
  • Theorem 3: CC21
  • Definition 4
  • Lemma 5
  • proof
  • Lemma 6
  • ...and 20 more