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Main Authors: Pratsiovytyi, M. V., Ratushniak, S. P., Vovk, Yu. Yu., Goncharenko, Ya. V.
Format: Preprint
Published: 2026
Subjects:
Online Access:https://arxiv.org/abs/2601.18610
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author Pratsiovytyi, M. V.
Ratushniak, S. P.
Vovk, Yu. Yu.
Goncharenko, Ya. V.
author_facet Pratsiovytyi, M. V.
Ratushniak, S. P.
Vovk, Yu. Yu.
Goncharenko, Ya. V.
contents For fixed natural numbers $r$ and $s$, where $2\leq s \leq r$, we consider a representation of numbers from the interval $[0;\frac{r}{s-1}]$ obtained by encoding numbers by means of the alphabet $A=\{0,1,...,r\}$ via the expansion $x=\sum\limits_{n=1}^{\infty}s^{-n}α_n=Δ^{r_s}_{α_1α_2...α_n...}.$ The algorithm for expanding a number into such a series is justified in the paper. The geometry of this representation is studied, including the geometric meaning of digits, properties of cylinder sets -- particularly the specificity of their overlaps -- and metric relations, as well as the connection between the representation and partial sums of the corresponding series. The paper also presents results on the study of a function $f$ defined by $f(x=\sum\limits_{n=1}^{\infty}\frac{α_n}{(r+1)^n})=Δ^{r_s}_{α_1α_2...α_n...}, α_n\in A.$ It is proved that the function $f$ is continuous at every point that has a unique representation in the classical numeration system with base $r+1$, and discontinuous at points having two representations. The function has unbounded variation and a self-affine graph. For $r<2s-1$, the function possesses singleton, finite, countable, and continuum level sets, including fractal ones; for $r>2s-2$, every level set is a continuum, and moreover it is fractal or anomalously fractal.
format Preprint
id arxiv_https___arxiv_org_abs_2601_18610
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Fractal functions defined in terms of number representations in systems with a redundant alphabet
Pratsiovytyi, M. V.
Ratushniak, S. P.
Vovk, Yu. Yu.
Goncharenko, Ya. V.
Number Theory
Functional Analysis
Primary: 11K55, Secondary: 26A30
For fixed natural numbers $r$ and $s$, where $2\leq s \leq r$, we consider a representation of numbers from the interval $[0;\frac{r}{s-1}]$ obtained by encoding numbers by means of the alphabet $A=\{0,1,...,r\}$ via the expansion $x=\sum\limits_{n=1}^{\infty}s^{-n}α_n=Δ^{r_s}_{α_1α_2...α_n...}.$ The algorithm for expanding a number into such a series is justified in the paper. The geometry of this representation is studied, including the geometric meaning of digits, properties of cylinder sets -- particularly the specificity of their overlaps -- and metric relations, as well as the connection between the representation and partial sums of the corresponding series. The paper also presents results on the study of a function $f$ defined by $f(x=\sum\limits_{n=1}^{\infty}\frac{α_n}{(r+1)^n})=Δ^{r_s}_{α_1α_2...α_n...}, α_n\in A.$ It is proved that the function $f$ is continuous at every point that has a unique representation in the classical numeration system with base $r+1$, and discontinuous at points having two representations. The function has unbounded variation and a self-affine graph. For $r<2s-1$, the function possesses singleton, finite, countable, and continuum level sets, including fractal ones; for $r>2s-2$, every level set is a continuum, and moreover it is fractal or anomalously fractal.
title Fractal functions defined in terms of number representations in systems with a redundant alphabet
topic Number Theory
Functional Analysis
Primary: 11K55, Secondary: 26A30
url https://arxiv.org/abs/2601.18610