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Journal articles

Boundary of central tiles associated with Pisot beta-numeration and purely periodic expansions

Shigeki Akiyama 1 Guy Barat 2 Valerie Berthe 3 Anne Siegel 4
3 ARITH - Arithmétique informatique
LIRMM - Laboratoire d'Informatique de Robotique et de Microélectronique de Montpellier
4 SYMBIOSE - Biological systems and models, bioinformatics and sequences
IRISA - Institut de Recherche en Informatique et Systèmes Aléatoires, Inria Rennes – Bretagne Atlantique
Abstract : This paper studies tilings and representation sapces related to the β-transformation when β is a Pisot number (that is not supposed to be a unit). The obtained results are applied to study the set of rational numbers having a purely periodic β-expansion. We indeed make use of the connection between pure periodicity and a compact self-similar representation of numbers having no fractional part in their β-expansion, called central tile: for elements x of the ring , so-called x-tiles are introduced, so that the central tile is a finite union of x-tiles up to translation. These x-tiles provide a covering (and even in some cases a tiling) of the space we are working in. This space, called complete representation space, is based on Archimedean as well as on the non-Archimedean completions of the number field TeX corresponding to the prime divisors of the norm of β. This representation space has numerous potential implications. We focus here on the gamma function γ(β) defined as the supremum of the set of elements v in [0, 1] such that every positive rational number p/q, with p/q ≤ v and q coprime with the norm of β, has a purely periodic β-expansion. The key point relies on the description of the boundary of the tiles in terms of paths on a graph called "boundary graph". The paper ends with explicit quadratic examples, showing that the general behaviour of γ(β) is slightly more complicated than in the unit case.
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Contributor : Anne Siegel Connect in order to contact the contributor
Submitted on : Tuesday, October 14, 2008 - 6:06:58 PM
Last modification on : Friday, February 4, 2022 - 3:09:40 AM

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Shigeki Akiyama, Guy Barat, Valerie Berthe, Anne Siegel. Boundary of central tiles associated with Pisot beta-numeration and purely periodic expansions. Monatshefte für Mathematik, Springer Verlag, 2008, 155 (3-4), pp.377-419. ⟨10.1007/s00605-008-0009-7⟩. ⟨inria-00330567⟩



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