English

Primitive algebraic points on curves

Number Theory 2024-05-21 v4

Abstract

A number field KK is primitive if KK and Q\mathbb{Q} are the only subextensions of KK. Let CC be a curve defined over Q\mathbb{Q}. We call an algebraic point PC(Q)P\in C(\overline{\mathbb{Q}}) primitive if the number field Q(P)\mathbb{Q}(P) is primitive. We present several sets of sufficient conditions for a curve CC to have finitely many primitive points of a given degree dd. For example, let C/QC/\mathbb{Q} be a hyperelliptic curve of genus gg, and let 3dg13 \le d \le g-1. Suppose that the Jacobian JJ of CC is simple. We show that CC has only finitely many primitive degree dd points, and in particular it has only finitely many degree dd points with Galois group SdS_d or AdA_d. However, for any even d4d \ge 4, a hyperelliptic curve C/QC/\mathbb{Q} has infinitely many imprimitive degree dd points whose Galois group is a subgroup of S2Sd/2S_2 \wr S_{d/2}.

Keywords

Cite

@article{arxiv.2306.17772,
  title  = {Primitive algebraic points on curves},
  author = {Maleeha Khawaja and Samir Siksek},
  journal= {arXiv preprint arXiv:2306.17772},
  year   = {2024}
}

Comments

Theorem 2 and Corollary 5 are strengthened and are now more easily applicable to modular curves

R2 v1 2026-06-28T11:19:08.419Z