Lower Bounds for Heights in Relative Galois Extensions

Abstract

The goal of this paper is to obtain lower bounds on the height of an algebraic number in a relative setting, extending previous work of Amoroso and Masser. Specifically, in our first theorem we obtain an effective bound for the height of an algebraic number $α$ when the base field $\mathbb{K}$ is a number field and $\mathbb{K}(α)/\mathbb{K}$ is Galois. Our second result establishes an explicit height bound for any non-zero element $α$ which is not a root of unity in a Galois extension $\mathbb{F}/\mathbb{K}$, depending on the degree of $\mathbb{K}/\mathbb{Q}$ and the number of conjugates of $α$ which are multiplicatively independent over $\mathbb{K}$. As a consequence, we obtain a height bound for such $α$ that is independent of the multiplicative independence condition.