A renormalization scheme for semi-regular continued fractions

Niels Langeveld, David Ralston

Research output: Contribution to journalArticleResearchpeer-review

Abstract

In this article we study a renormalization scheme with which we find all semi-regular continued fractions of a number in a natural way. We define two maps, T^ slow and T^ fast: these maps are defined for (x,y)∈[0,1], where x is the number for which a semi- regular continued fraction representation is developed by T^ slow according to the parameter y. The set of all possible semi-regular continued fraction representations of x are bijectively constructed as the parameter y varies. The map T^ fast is a “sped up" version of the map T^ slow, and we show that T^ fast is ergodic with respect to a probability measure which is mutually absolutely continuous with Lebesgue measure. In contrast, T^ slow preserves no such measure, but does preserve an infinite, σ-finite measure mutually absolutely continuous with Lebesgue measure. Furthermore, we generate a sequence of substitutions which generate a symbolic coding of the orbit of y under rotation by x modulo one. In the last section we highlight how our scheme can be used to generate semi-regular continued fractions explicitly for specific continued fraction algorithms such as Nakada’s α-continued fractions.

Original languageEnglish
Number of pages36
JournalMonatshefte für Mathematik
Volume??? Stand: 12. November 2024
DOIs
Publication statusPublished - 30 Oct 2024

Bibliographical note

Publisher Copyright: © The Author(s) 2024.

Keywords

  • 11A55
  • 11J70
  • 37A44
  • 37B10
  • 37E05
  • Approximating sequences
  • Circle rotations
  • Renormalization
  • Semi-regular continued fractions
  • Symbolic encodings

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