<p>We consider Cantor real numeration system as a frame in which every non-negative real number has a positional representation. The system is defined using a bi-infinite sequence <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10474_2025_1535_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="89" /> </InlineMediaObject> <EquationSource Format="TEX">\(B=(\beta_n)_{n\in\mathbb{Z}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>B</mi> <mo>=</mo> <msub> <mrow> <mo stretchy="false">(</mo> <msub> <mi>β</mi> <mi>n</mi> </msub> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>n</mi> <mo>∈</mo> <mi mathvariant="double-struck">Z</mi> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation> of real numbers greater than one. We introduce the set of <i>B</i>-integers and code the sequence of gaps between consecutive <i>B</i>-integers by a symbolic sequence in general over the alphabet <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10474_2025_1535_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathbb{N}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">N</mi> </math></EquationSource> </InlineEquation>. We show that this sequence is <i>S</i>-adic. We focus on alternate base systems, where the sequence <i>B</i> of bases is periodic, and characterize alternate bases <i>B</i> in which <i>B</i>-integers can be coded by using a symbolic sequence <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10474_2025_1535_Article_IEq3.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">\(\bf{v}_{\it B}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="bold">v</mi> <mi mathvariant="italic">B</mi> </msub> </math></EquationSource> </InlineEquation> over a finite alphabet. With these so-called Parry alternate bases we associate some morphisms and show that <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10474_2025_1535_Article_IEq3.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">\(\bf{v}_{\it B}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="bold">v</mi> <mi mathvariant="italic">B</mi> </msub> </math></EquationSource> </InlineEquation> is a fixed point of their composition. We then provide two classes of Parry alternate bases <i>B</i> generating sturmian fixed points. The paper generalizes results of Fabre and Burdík et al. obtained for the Rényi numerations systems, i.e., in the case when the Cantor base <i>B</i> is a constant sequence.</p>

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Substitutions and Cantor real numeration systems

  • É. Charlier,
  • C. Cisternino,
  • Z. Masáková,
  • E. Pelantová

摘要

We consider Cantor real numeration system as a frame in which every non-negative real number has a positional representation. The system is defined using a bi-infinite sequence \(B=(\beta_n)_{n\in\mathbb{Z}}\) B = ( β n ) n Z of real numbers greater than one. We introduce the set of B-integers and code the sequence of gaps between consecutive B-integers by a symbolic sequence in general over the alphabet \(\mathbb{N}\) N . We show that this sequence is S-adic. We focus on alternate base systems, where the sequence B of bases is periodic, and characterize alternate bases B in which B-integers can be coded by using a symbolic sequence \(\bf{v}_{\it B}\) v B over a finite alphabet. With these so-called Parry alternate bases we associate some morphisms and show that \(\bf{v}_{\it B}\) v B is a fixed point of their composition. We then provide two classes of Parry alternate bases B generating sturmian fixed points. The paper generalizes results of Fabre and Burdík et al. obtained for the Rényi numerations systems, i.e., in the case when the Cantor base B is a constant sequence.