Classical mechanics and the propagation of the discontinuities of the quantum wave function

Geometrical optics can be regarded both as the short-wavelength approximation of the propagation of electromagnetic waves, and as the exact way in which propagate the surfaces of discontinuity of the classical electromagnetic field. In this work we translate this last idea to quantum mechanics (both relativistic and nonrelativistic). We find that the surfaces of discontinuity of the wave function propagate exactly following the classical trajectories determined by the Hamilton-Jacobi equation. As an example, we consider the lack of diffraction of abrupt wave fronts.