Uniqueness of photon sphere for Reissner-Nordström electric-magnetic system

Abstract: Uniqueness of static, asymptotically flat, non-extremal {\it photon sphere} in Einstein-Maxwell spacetime with electric and magnetic charges has been proved. Using conformal positive energy theorem, as well as, the positive mass theorem and adequate conformal transformations, we envisage the two alternative ways of proving that the exterior region of a certain radius of the studied static {\it photon sphere}, is characterized by ADM mass, electric and magnetic charges.