The phase of a quantum mechanical particle in curved spacetime

We investigate the quantum mechanical wave equations for free particles of spin 0, 1/2, 1 in the background of an arbitrary static gravitational field in order to explicitly determine if the phase of the wavefunction is S/(h) over bar = integral p(mu) dx(mu)/(h) over bar, as is often quoted in the l iterature. We work in isotropic coordinates where the wave equations have a simple manageable form and do not make a weak gravitational field approxim ation. We interpret these wave equations in terms of a quantum mechanical p article moving in medium with a spatially varying effective index of refrac tion. Due to the first order spatial derivative structure of the Dirac equa tion in curved spacetime, only the spin 1/2 particle has exactly the quantu m mechanical phase as indicated above. The second order spatial derivative structure of the spin 0 and spin I wave equations yield the above phase onl y to lowest order in (h) over bar. We develop a WKB approximation for the s olution of the spin 0 and spin 1 wave equations and explore amplitude and p hase corrections beyond the lowest order in (h) over bar, For the spin 1/2 particle we calculate the phase appropriate for neutrino flavor oscillation s.