On Orders in Number Fields: Picard Groups, Ring Class Fields and Applications

In this article, we focus on orders in arbitrary number fields, consider their Picard groups and finally obtain ring class fields corresponding to them. The Galois group of the ring class field is isomorphic to the Picard group. As an application, we give criteria of the solvability of the diophantine equation $p=x^2+n{y}^2$ over a class of imaginary quadratic fields where $p$ is a prime element.