A Covariant Path Amplitude Description of Flavour Oscillations: The   Gribov-Pontecorvo Phase for Neutrino Vacuum Propagation is Right
  An extended study is performed of geometrical and kinematical assumptions used in calculations of the neutrino oscillation phase. The almost universally employed `equal velocity' assumption, in which all neutrino mass eigenstates are produced at the same time, is shown to underestimate, by a factor of two, the neutrino propagation contribution to the phase. Taking properly into account, in a covariant path amplitude calculation, the incoherent nature of neutrino production as predicted by the Standard Model, results in an important source propagator contribution to the phase. It is argued that the commonly discussed Gaussian `wave packets' have no basis within quantum mechanics and are the result of a confused amalgam of quantum and classical wave concepts. 
J.H.Field (D\'epartement de Physique Nucl\'eaire et Corpusculaire   Universit\'e de Gen\`eve)