Neutrino oscillations in nonuniform matter

We examine the effect of flavor-dependent elastic scattering upon neutrino flavor vacuum oscillations. The results are derived from a first-principles Dirac equation for the phenomenon. The conjecture of Wolfenstein is validated (with a correction G→ √2 G as noted in more recent literature) for a homogeneous medium. While the differential equation obtained for the extension to a non- homogeneous case appears to differ significantly from that which has been used in the literature heretofore, we are able to show that they are equivalent for densities that vary little over the neutrino's de Broglie wavelength