English

Effective bounds for adelic Galois representations attached to elliptic curves over the rationals

Number Theory 2026-03-02 v3 Algebraic Geometry

Abstract

Given an elliptic curve EE defined over Q\mathbb{Q} without complex multiplication, we provide an explicit sharp bound on the index of the image of the adelic representation ρE\rho_E. In particular, if hF(E)\operatorname{h}_{\mathcal{F}}(E) is the stable Faltings height of EE, we show that [GL2(Z^):ImρE][\operatorname{GL}_2(\widehat{\mathbb{Z}}) : \operatorname{Im}\rho_E] is bounded above by 1021(hF(E)+40)4.4210^{21} (\operatorname{h}_{\mathcal{F}}(E)+40)^{4.42}, and, for hF(E)\operatorname{h}_{\mathcal{F}}(E) tending to infinity, by hF(E)3+o(1)\operatorname{h}_{\mathcal{F}}(E)^{3+o(1)}. We also classify the possible (conjecturally non-existent) images of the representations ρE,pn\rho_{E,p^n} whenever ImρE,p\operatorname{Im}\rho_{E,p} is contained in the normaliser of a non-split Cartan. This result improves previous work of Zywina and Lombardo.

Keywords

Cite

@article{arxiv.2412.10340,
  title  = {Effective bounds for adelic Galois representations attached to elliptic curves over the rationals},
  author = {Lorenzo Furio},
  journal= {arXiv preprint arXiv:2412.10340},
  year   = {2026}
}

Comments

55 pages. The numbering of the theorems has changed from previous versions