Published online by Cambridge University Press: 20 November 2018
Consider a Shimura curve $X_{0}^{D}\left( N \right)$ over the rational numbers. We determine criteria for the twist by an Atkin–Lenher involution to have points over a local field. As a corollary we give a new proof of the theorem of Jordan and Livné on
${{\mathbf{Q}}_{p}}$ points when
$p|D$ and for the first time give criteria for
${{\mathbf{Q}}_{p}}$ points when
$p|N$. We also give congruence conditions for roots modulo
$p$ of Hilbert class polynomials.
The author was partially supported by NSF VIGRE grant DMS-0738586 and the University of Georgia Dissertation completion award.