Counting elliptic curves over $\mathbb{Q}$ with bounded naive height

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Auteurs principaux: Barquero-Sanchez, Adrian, Mora-Mora, Daniel
Format: Preprint
Publié: 2025
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author Barquero-Sanchez, Adrian
Mora-Mora, Daniel
author_facet Barquero-Sanchez, Adrian
Mora-Mora, Daniel
contents In this paper, we give exact and asymptotic formulas for counting elliptic curves $ E_{A,B} \colon y^2 = x^3 + Ax + B $ with $ A, B \in \mathbb{Z} $, ordered by naive height. We study the family of all such curves and also several natural subfamilies, including those with fixed $ j $-invariant and those with complex multiplication (CM). In particular, we provide formulas for two commonly used normalizations of the naive height appearing in the literature: the calibrated naive height, defined by \[ H^{\mathrm{cal}}(E_{A,B}) := \max\{ 4|A|^3, 27B^2 \}, \] and the uncalibrated naive height, defined by \[ H^{\mathrm{ncal}}(E_{A,B}) := \max\{ |A|^3, B^2 \}. \] In fact, we prove our theorems with respect to the more general naive height $H_{α, β}(E_{A,B}) := \max\{ α|A|^3, βB^2 \}$, defined for arbitrary positive real numbers $α, β\in \mathbb{R}_{> 0}$. As part of our approach, we give a completely explicit parametrization of the set of curves $ E_{A,B} $ with fixed $ j $-invariant and bounded naive height, describing them as twists of the curve $ E_{A_j, B_j} $ of minimal naive height for the given $ j $-invariant. We also include tables comparing and verifying our theoretical predictions with exact counts obtained via exhaustive computer searches, and we compute data for CM elliptic curves of naive height up to $ 10^{30} $. Code in SageMath is provided to compute all exact and asymptotic formulas appearing in the paper.
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id arxiv_https___arxiv_org_abs_2506_18874
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Counting elliptic curves over $\mathbb{Q}$ with bounded naive height
Barquero-Sanchez, Adrian
Mora-Mora, Daniel
Number Theory
Algebraic Geometry
11G05 (Primary) 11G15, 11N45 (Secondary)
In this paper, we give exact and asymptotic formulas for counting elliptic curves $ E_{A,B} \colon y^2 = x^3 + Ax + B $ with $ A, B \in \mathbb{Z} $, ordered by naive height. We study the family of all such curves and also several natural subfamilies, including those with fixed $ j $-invariant and those with complex multiplication (CM). In particular, we provide formulas for two commonly used normalizations of the naive height appearing in the literature: the calibrated naive height, defined by \[ H^{\mathrm{cal}}(E_{A,B}) := \max\{ 4|A|^3, 27B^2 \}, \] and the uncalibrated naive height, defined by \[ H^{\mathrm{ncal}}(E_{A,B}) := \max\{ |A|^3, B^2 \}. \] In fact, we prove our theorems with respect to the more general naive height $H_{α, β}(E_{A,B}) := \max\{ α|A|^3, βB^2 \}$, defined for arbitrary positive real numbers $α, β\in \mathbb{R}_{> 0}$. As part of our approach, we give a completely explicit parametrization of the set of curves $ E_{A,B} $ with fixed $ j $-invariant and bounded naive height, describing them as twists of the curve $ E_{A_j, B_j} $ of minimal naive height for the given $ j $-invariant. We also include tables comparing and verifying our theoretical predictions with exact counts obtained via exhaustive computer searches, and we compute data for CM elliptic curves of naive height up to $ 10^{30} $. Code in SageMath is provided to compute all exact and asymptotic formulas appearing in the paper.
title Counting elliptic curves over $\mathbb{Q}$ with bounded naive height
topic Number Theory
Algebraic Geometry
11G05 (Primary) 11G15, 11N45 (Secondary)
url https://arxiv.org/abs/2506.18874