t-periodic light rays in conformally stationary spacetimes via Finsler geometry

In this paper we prove several multiplicity results of t-periodic light rays in conformally stationary spacetimes using the Fermat metric and the extensions of the classical theorems of Gromoll-Meyer and Bangert- Hingston to Finsler manifolds. Moreover, we exhibit some stationary spacetimes with a nite number of t-periodic light rays and compute a lower bound for the period of the light rays when the ag curvature of the Fermat metric is -pinched.