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.