English

Determining monogenity of pure cubic number fields using elliptic curves

Number Theory 2025-06-12 v2

Abstract

We study monogenity of pure cubic number fields by means of Selmer groups of certain elliptic curves. A cubic number field with discriminant DD determines a unique nontrivial F3\mathbb{F}_3-orbit in the first cohomology group of the elliptic curve ED:y2=4x3+DE^D: y^2 = 4x^3 + D with respect to a certain 3-isogeny ϕ\phi. Orbits corresponding to monogenic fields must lie in the soluble part of the Selmer group Sϕ(ED/Q)S^{\phi}(E^D/\mathbb{Q}), and this gives a criterion to discard monogenity. From this, we can derive bounds on the number of monogenic cubic fields in terms of the rank of the elliptic curve. We can also determine the monogenity of many concrete pure cubic fields assuming GRH.

Keywords

Cite

@article{arxiv.2505.06213,
  title  = {Determining monogenity of pure cubic number fields using elliptic curves},
  author = {Jordi Guàrdia and Francesc Pedret},
  journal= {arXiv preprint arXiv:2505.06213},
  year   = {2025}
}

Comments

Added the hypothesis that $\mathcal{O}_L$ is free over $\mathcal{O}_K$ to the main theorem, as this condition is necessary for our methods to apply. Since our primary focus is the case $K = \mathbb{Q}$, this correction does not impact our other results or computations

R2 v1 2026-06-28T23:27:30.895Z