Möbius inversion and coprime summation for error-sum functions of continued fractions

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Main Author: Ahn, Min Woong
Format: Preprint
Published: 2025
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author Ahn, Min Woong
author_facet Ahn, Min Woong
contents We study the unweighted error-sum function $\mathcal{E}(x) \coloneqq \sum_{n \geq 0} ( x- p_n(x)/q_n(x) )$, where $p_n(x)/q_n(x)$ is the $n$th convergent of the continued fraction expansion of $x \in \mathbb{R}$. We prove that the Hausdorff dimension of the graph of $\mathcal{E}$ is exactly equal to $1$. Our proof is number-theoretic in nature and involves Möbius inversion, summation over coprime convergent denominators, and precise upper bounds derived via continued fraction recurrence relations. As a supplementary result, we rederive the known upper bound of $3/2$ for the Hausdorff dimension of the graph of the relative error-sum function $P(x) \coloneqq \sum_{n \geq 0} (q_n(x)x-p_n(x))$.
format Preprint
id arxiv_https___arxiv_org_abs_2507_16536
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Möbius inversion and coprime summation for error-sum functions of continued fractions
Ahn, Min Woong
Number Theory
Classical Analysis and ODEs
Primary 11A55, 11K50, Secondary 26A18, 28A80, 37E05, 33E20
We study the unweighted error-sum function $\mathcal{E}(x) \coloneqq \sum_{n \geq 0} ( x- p_n(x)/q_n(x) )$, where $p_n(x)/q_n(x)$ is the $n$th convergent of the continued fraction expansion of $x \in \mathbb{R}$. We prove that the Hausdorff dimension of the graph of $\mathcal{E}$ is exactly equal to $1$. Our proof is number-theoretic in nature and involves Möbius inversion, summation over coprime convergent denominators, and precise upper bounds derived via continued fraction recurrence relations. As a supplementary result, we rederive the known upper bound of $3/2$ for the Hausdorff dimension of the graph of the relative error-sum function $P(x) \coloneqq \sum_{n \geq 0} (q_n(x)x-p_n(x))$.
title Möbius inversion and coprime summation for error-sum functions of continued fractions
topic Number Theory
Classical Analysis and ODEs
Primary 11A55, 11K50, Secondary 26A18, 28A80, 37E05, 33E20
url https://arxiv.org/abs/2507.16536