Counting Imaginary Quadratic Fields with an Ideal Class Group of 5-rank at least 2

Fuente: arXiv
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Auteurs principaux: Bartz, Kollin, Levin, Aaron, Thamminana, Aman Dhruva
Format: Preprint
Publié: 2025
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author Bartz, Kollin
Levin, Aaron
Thamminana, Aman Dhruva
author_facet Bartz, Kollin
Levin, Aaron
Thamminana, Aman Dhruva
contents We prove that there are $\gg\frac{X^{\frac{1}{3}}}{(\log X)^2}$ imaginary quadratic fields $k$ with discriminant $|d_k|\leq X$ and an ideal class group of $5$-rank at least $2$. This improves a result of Byeon, who proved the lower bound $\gg X^{\frac{1}{4}}$ in the same setting. We use a method of Howe, Leprévost, and Poonen to construct a genus $2$ curve $C$ over $\mathbb{Q}$ such that $C$ has a rational Weierstrass point and the Jacobian of $C$ has a rational torsion subgroup of $5$-rank $2$. We deduce the main result from the existence of the curve $C$ and a quantitative result of Kulkarni and the second author.
format Preprint
id arxiv_https___arxiv_org_abs_2502_00845
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Counting Imaginary Quadratic Fields with an Ideal Class Group of 5-rank at least 2
Bartz, Kollin
Levin, Aaron
Thamminana, Aman Dhruva
Number Theory
11R29, 11R11
We prove that there are $\gg\frac{X^{\frac{1}{3}}}{(\log X)^2}$ imaginary quadratic fields $k$ with discriminant $|d_k|\leq X$ and an ideal class group of $5$-rank at least $2$. This improves a result of Byeon, who proved the lower bound $\gg X^{\frac{1}{4}}$ in the same setting. We use a method of Howe, Leprévost, and Poonen to construct a genus $2$ curve $C$ over $\mathbb{Q}$ such that $C$ has a rational Weierstrass point and the Jacobian of $C$ has a rational torsion subgroup of $5$-rank $2$. We deduce the main result from the existence of the curve $C$ and a quantitative result of Kulkarni and the second author.
title Counting Imaginary Quadratic Fields with an Ideal Class Group of 5-rank at least 2
topic Number Theory
11R29, 11R11
url https://arxiv.org/abs/2502.00845