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Auteurs principaux: Abramson, Heather, Chesebro, Eric, Cummins, Vivian, Emlen, Cory, Ke, Kenton, Grady, Ryan
Format: Preprint
Publié: 2023
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Accès en ligne:https://arxiv.org/abs/2308.04654
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author Abramson, Heather
Chesebro, Eric
Cummins, Vivian
Emlen, Cory
Ke, Kenton
Grady, Ryan
author_facet Abramson, Heather
Chesebro, Eric
Cummins, Vivian
Emlen, Cory
Ke, Kenton
Grady, Ryan
contents This paper concerns the relationships between continued fractions and the geometry of the Stern-Brocot diagram. Each rational number can be expressed as a continued fraction $[a_0; a_1, \ldots, a_n]$ whose terms $a_i$ are integers and are positive if $i \geq 1$. Select an index $i \in \{ 1, \ldots, n \}$ and replace $a_i$ with an integer $m$ to obtain a continued fraction expansion for an extended rational $α_m \in \mathbb{Q} \cup \{ \infty \}$. This paper shows that the vertices of the Stern-Brocot diagram corresponding to the numbers $\{ α_m \}_{m \in \mathbb{Z}}$ lie on a pair of (extended) Euclidean lines across the diagram. The slopes of these two lines differ only by a sign change and they meet at the point $L=\left([a_0; a_1, \ldots, a_{i-1}], 0\right) \in \mathbb{R}^2$. Moreover, as $\lvert m \rvert \to \infty$, the associated vertices move down these lines and converge to $L$. This paper concludes with a discussion which interprets this result in the context of 2-bridge link complements and Thurston's work on hyperbolic Dehn surgery.
format Preprint
id arxiv_https___arxiv_org_abs_2308_04654
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Continued fractions and lines across the Stern--Brocot diagram
Abramson, Heather
Chesebro, Eric
Cummins, Vivian
Emlen, Cory
Ke, Kenton
Grady, Ryan
Geometric Topology
Combinatorics
57M50, 11B57
This paper concerns the relationships between continued fractions and the geometry of the Stern-Brocot diagram. Each rational number can be expressed as a continued fraction $[a_0; a_1, \ldots, a_n]$ whose terms $a_i$ are integers and are positive if $i \geq 1$. Select an index $i \in \{ 1, \ldots, n \}$ and replace $a_i$ with an integer $m$ to obtain a continued fraction expansion for an extended rational $α_m \in \mathbb{Q} \cup \{ \infty \}$. This paper shows that the vertices of the Stern-Brocot diagram corresponding to the numbers $\{ α_m \}_{m \in \mathbb{Z}}$ lie on a pair of (extended) Euclidean lines across the diagram. The slopes of these two lines differ only by a sign change and they meet at the point $L=\left([a_0; a_1, \ldots, a_{i-1}], 0\right) \in \mathbb{R}^2$. Moreover, as $\lvert m \rvert \to \infty$, the associated vertices move down these lines and converge to $L$. This paper concludes with a discussion which interprets this result in the context of 2-bridge link complements and Thurston's work on hyperbolic Dehn surgery.
title Continued fractions and lines across the Stern--Brocot diagram
topic Geometric Topology
Combinatorics
57M50, 11B57
url https://arxiv.org/abs/2308.04654