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Ideal Classes of Order 2n in a Family of Totally Real Cubic Fields and Rational Points on Associated Elliptic Curves
Abstract
For every prime ℓ≥5 and integer n≥2, we construct a totally real cubic field in the family studied by Ennola with a specified prime ideal above ℓ whose class has exact order 2n. For parameters satisfying two square conditions and explicit congruences, the same squareclass obstructions give four independent rational points on the associated elliptic curves. A Pell equation describes all such parameters. A genus-one base change gives five independent sections that generate a subgroup saturated at two. It also yields infinitely many elliptic curves over ℚ, pairwise nonisomorphic over ℚ̅, with rank at least five.
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BibTeX
@misc{lu2026ideal,
title = {{Ideal Classes of Order $2^n$ in a Family of Totally Real Cubic Fields and Rational Points on Associated Elliptic Curves}},
author = {Junyu Lu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.04254},
eprint = {2610.04254},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.04254},
}
RIS
TY - UNPB
TI - Ideal Classes of Order 2^n in a Family of Totally Real Cubic Fields and Rational Points on Associated Elliptic Curves
AU - Junyu Lu
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.04254
UR - https://arxiv.org/abs/2610.04254
AB - For every prime ℓ≥5 and integer n≥2, we construct a totally real cubic field in the family studied by Ennola with a specified prime ideal above ℓ whose class has exact order 2^n. For parameters satisfying two square conditions and explicit congruences, the same squareclass obstructions give four independent rational points on the associated elliptic curves. A Pell equation describes all such parameters. A genus-one base change gives five independent sections that generate a subgroup saturated at two. It also yields infinitely many elliptic curves over ℚ, pairwise nonisomorphic over ℚ̅, with rank at least five.
ER -