English

Lower bounds for the modified Szpiro ratio

Number Theory 2023-06-21 v2

Abstract

Let E/QE/\mathbb{Q} be an elliptic curve. The modified Szpiro ratio of EE is the quantity σm(E)=logmax{c43,c62}/logNE\sigma_{m}(E) =\log\max\left\{ \left\vert c_{4}^{3}\right\vert ,c_{6}^{2}\right\} /\log N_{E} where c4c_{4} and c6c_{6} are the invariants associated to a global minimal model of EE, and NEN_{E} denotes the conductor of EE. In this article, we show that for each of the fifteen torsion subgroups TT allowed by Mazur's Torsion Theorem, there is a rational number lTl_{T} such that if TE(Q)torsT\hookrightarrow E(\mathbb{Q}) _{\text{tors}}, then σm(E)>lT\sigma_{m}(E) >l_{T}. We also show that this bound is sharp.

Keywords

Cite

@article{arxiv.2104.10817,
  title  = {Lower bounds for the modified Szpiro ratio},
  author = {Alexander J. Barrios},
  journal= {arXiv preprint arXiv:2104.10817},
  year   = {2023}
}

Comments

15 pages; incorporates referee's suggestions; sharpness of lower bounds is no longer conditional on the abc conjecture; final version to appear in Acta Arithmetica

R2 v1 2026-06-24T01:25:00.772Z