Linear Differential Operators for Polynomial Equations

Given a squarefree polynomial P k0[ x,y ], k0a number field, we construct a linear differential operator that allows one to calculate the genus of the complex curve defined by P = 0 (when P is absolutely irreducible), the absolute factorization of P over the algebraic closure of k0, and calculate information concerning the Galois group of P over ___ k0(x) as well as overk0 (x).