The maximal abelian extension contained in a division field of an elliptic curve over $\mathbb{Q}$ with complex multiplication (2408.16164v1)

Abstract: Let $K$ be an imaginary quadratic field, and let $\mathcal{O}{K,f}$ be an order in $K$ of conductor $f\geq 1$. Let $E$ be an elliptic curve with CM by $\mathcal{O}{K,f}$, such that $E$ is defined by a model over $\mathbb{Q}(j_{K,f})$, where $j_{K,f}=j(E)$. It has been shown by the author and Lozano-Robledo that $\operatorname{Gal}(\mathbb{Q}(j_{K,f},E[N])/\mathbb{Q}(j_{K,f}))$ is only abelian for $N=2,3$, and $4$. Let $p$ be a prime and let $n\geq 1$ be an integer. In this article, we bound the commutator subgroups of $\operatorname{Gal}(\mathbb{Q}(E[p^n])/\mathbb{Q})$ and classify the maximal abelian extensions contained in $\mathbb{Q}(E[p^n])/\mathbb{Q}$.