Motion of a Vector Particle in a Curved Spacetime. II First Order   Correction to a Geodesic in a Schwarzschild Background
  The influence of spin on a photon's motion in a Schwarzschild and FRW spacetimes is studied. The first order correction to the geodesic motion is found. It is shown that unlike the world-lines of spinless particles, the photons world-lines do not lie in a plane. 
Z. Turakulov, M. Safonova