An Elliptic Curve Analogue of Pillai's Lower Bound on Primitive Roots

TL;DR

This paper establishes lower bounds on the smallest x-coordinate of a maximal order point on elliptic curves over finite fields, extending classical primitive root bounds to elliptic curve settings.

Contribution

It provides unconditional and GRH-assuming lower bounds for the minimal x-coordinate of points of maximal order on elliptic curves over finite fields, analogous to primitive root bounds.

Findings

Unconditional lower bound: r(E,p) > 0.72 log log p for infinitely many p.

Conditional lower bound under GRH: r(E,p) > 0.36 log p.

Extension of classical primitive root bounds to elliptic curve context.

Abstract

Let $E/\mathbb{Q}$ be an elliptic curve. For a prime $p$ of good reduction, let $r(E,p)$ be the smallest non-negative integer that gives the $x$-coordinate of a point of maximal order in the group $E(\mathbb{F}_p)$. We prove unconditionally that $r(E,p)> 0.72\log\log p$ for infinitely many $p$, and $r(E,p) > 0.36 \log p$ under the assumption of the Generalized Riemann Hypothesis. This can be viewed as elliptic curve analogues of classical lower bounds on the least primitive root of a prime.