Published online by Cambridge University Press: 20 November 2018
Let $k$ be a global field,
$\bar{k}$ a separable closure of
$k$, and
${{G}_{k}}$ the absolute Galois group Gal
$(\bar{k}/k)$ of
$\bar{k}$ over
$k$. For every
$\sigma \,\in \,{{G}_{K}}$, let
${{\bar{k}}^{\sigma }}$ be the fixed subfield of
$\bar{k}$ under
$\sigma$. Let
$E/k$ be an elliptic curve over
$k$. It is known that the Mordell–Weil group
$E({{\bar{k}}^{\sigma }})$ has infinite rank. We present a new proof of this fact in the following two cases. First, when
$k$ is a global function field of odd characteristic and
$E$ is parametrized by a Drinfeld modular curve, and secondly when
$k$ is a totally real number field and
$E/k$ is parametrized by a Shimura curve. In both cases our approach uses the non-triviality of a sequence of Heegner points on
$E$ defined over ring class fields.