Reductions of points on algebraic groups
Abstract
Let be the product of an abelian variety and a torus defined over a number field . Fix some prime number . If is a point of infinite order, we consider the set of primes of such that the reduction is well-defined and has order coprime to . This set admits a natural density. By refining the method of R.~Jones and J.~Rouse (2010), we can express the density as an -adic integral without requiring any assumption. We also prove that the density is always a rational number whose denominator (up to powers of ) is uniformly bounded in a very strong sense. For elliptic curves, we describe a strategy for computing the density which covers every possible case.
Cite
@article{arxiv.1612.02847,
title = {Reductions of points on algebraic groups},
author = {Davide Lombardo and Antonella Perucca},
journal= {arXiv preprint arXiv:1612.02847},
year = {2023}
}
Comments
v2: we show that the densities we are interested in are rational numbers and prove results on the structure of their denominators. References updated to reflect small changes in https://arxiv.org/abs/1612.02845