In this thesis we propose a curved spacetime version of the Dirac equation. Thernequation has been developed mainly to try and account in a natural way for thernsolution of the Dirac equation in curved spacetime in an open cosmological universernwith a partially horn topology in the presence of a time dependent magneticrn eld. Since the exact solution cannot be obtained explicitly for arbitrary timerndependence of the eld, we discuss the asymptotic behavior of the solutions withrnthe help of the relativistic Hamilton-Jacobi equation