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A one-parameter family of fractal functions related with the $Q_s$-representation of real numbers
Pratsiovytyi Mykola 1,2 , Nazarchuk Valentyna 1 , Vasylenko Natalya Anatolyivna 1
1 Department of dynamic systems and fractal analysis, Institute of Mathematics of the National Academy of Sciences of Ukraine, Kyiv, 01001, Ukraine
2 Department of Higher Mathematics, National Pedagogical Dragomanov University, Kyiv, 01001, Ukraine
Keywords: $Q_s$-representation of numbers, $Q_s$-binary number, $Q_s$-unary number, cylinder, Cantor type set, Hausdorff-Besicovitch dimension, fractal function, singular function, inversor of $Q_2$-representation of numbers
Abstract

In the paper we consider a continuum class functions defined by terms of the $Q_s$-representation of real numbers on the segment $[0;1]$, which generalizes the classical $s$-adic representation. The dependence of the $n$-th digit of the $Q_s$-representation of the function value is specified by a finite function $\varphi_n(a_n,\alpha_n)$ of two variables, whose arguments are the corresponding $Q_s$-digits $\alpha_n(x)$ and $a_n(a)$ of the input
$x$ and the parameter $a$, respectively.

We prove continuity of each function in this class at every $Q_s$-unary number, i.e., at points possessing a unique $Q_s$-representation. Necessary and sufficient conditions for continuity on the entire domain are established. Conditions involving the digits of the parameter $a$ and the sequence of defining functions $(\varphi_n)$, under which the function $f_a$ admits finite or continuum cardinality level sets are obtained.

For particular cases ($s=2$), we study integral and differential properties, as well as the fractal properties of the sets of values. Using the self-similarity properties of the function graph and the established connection between the functions under consideration and the inversor of digits of the $Q_2$-representation of numbers, we compute the Lebesgue integral of these functions. Furthermore, we identify a subclass of functions that are piecewise singular or singular on intervals; that is, continuous non-constant functions whose derivative is zero almost everywhere in the sense of Lebesgue measure.

References

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Published Online 12/12/2025
Cite
ACS Style
Pratsiovytyi, M.; Nazarchuk, V.; Vasylenko, N.A. A one-parameter family of fractal functions related with the $Q_s$-representation of real numbers. Bukovinian Mathematical Journal. 2025, 13 https://doi.org/https://doi.org/10.31861/bmj2025.02.10
AMA Style
Pratsiovytyi M, Nazarchuk V, Vasylenko NA. A one-parameter family of fractal functions related with the $Q_s$-representation of real numbers. Bukovinian Mathematical Journal. 2025; 13(2). https://doi.org/https://doi.org/10.31861/bmj2025.02.10
Chicago/Turabian Style
Mykola Pratsiovytyi, Valentyna Nazarchuk, Natalya Anatolyivna Vasylenko. 2025. "A one-parameter family of fractal functions related with the $Q_s$-representation of real numbers". Bukovinian Mathematical Journal. 13 no. 2. https://doi.org/https://doi.org/10.31861/bmj2025.02.10
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