The automorphism group of the non-split Cartan modular curve of level 11

Valerio Dose, Julio Fernández, Josep González +1

We derive equations for the modular curve $X_{ns}(11)$ associated to a non-split Cartan subgroup of ${\mathrm{GL}}_2({\mathbf{F}}_{11})$. This allows us to compute the automorphism g…