Rational Preperiodic Points of Quadratic Rational Maps over $\mathbb{Q}$ with Nonabelian Automorphism Groups

Fuente: arXiv
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Main Authors: Bilgili, Hasan, Sadek, Mohammad
Format: Preprint
Published: 2026
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author Bilgili, Hasan
Sadek, Mohammad
author_facet Bilgili, Hasan
Sadek, Mohammad
contents Let $f:\mathbb{P}^1\rightarrow\mathbb{P}^1$ be a quadratic rational map defined over the rational field $\mathbb{Q}$ with nonabelian automorphism group. We prove that no such map has a $\mathbb{Q}$-rational periodic point with exact period $N\ge 4$. We also give an explicit parametrization of such maps that have $\mathbb{Q}$-rational periodic points of period $1$, $2$, and $3$. Consequently, we show that the number of $\mathbb{Q}$-rational preperiodic points of such a map is at most $6$; establishing Morton-Silverman Uniform Boundedness Conjecture for this family of quadratic rational maps. As a result, we completely classify all portraits of $\mathbb{Q}$-rational preperiodic points for such $f$ showing that there are exactly $5$ such portraits.
format Preprint
id arxiv_https___arxiv_org_abs_2603_06203
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Rational Preperiodic Points of Quadratic Rational Maps over $\mathbb{Q}$ with Nonabelian Automorphism Groups
Bilgili, Hasan
Sadek, Mohammad
Number Theory
Dynamical Systems
37P05, 37P15
Let $f:\mathbb{P}^1\rightarrow\mathbb{P}^1$ be a quadratic rational map defined over the rational field $\mathbb{Q}$ with nonabelian automorphism group. We prove that no such map has a $\mathbb{Q}$-rational periodic point with exact period $N\ge 4$. We also give an explicit parametrization of such maps that have $\mathbb{Q}$-rational periodic points of period $1$, $2$, and $3$. Consequently, we show that the number of $\mathbb{Q}$-rational preperiodic points of such a map is at most $6$; establishing Morton-Silverman Uniform Boundedness Conjecture for this family of quadratic rational maps. As a result, we completely classify all portraits of $\mathbb{Q}$-rational preperiodic points for such $f$ showing that there are exactly $5$ such portraits.
title Rational Preperiodic Points of Quadratic Rational Maps over $\mathbb{Q}$ with Nonabelian Automorphism Groups
topic Number Theory
Dynamical Systems
37P05, 37P15
url https://arxiv.org/abs/2603.06203