In a recent paper, the authors established the uniqueness of photon spheres
in static vacuum asymptotically flat spacetimes by adapting Bunting and
Masood-ul-Alam's proof of static vacuum black hole uniqueness. Here, we
establish uniqueness of suitably defined sub-extremal photon spheres in static
electro-vacuum asymptotically flat spacetimes by adapting the argument of
Masood-ul-Alam. As a consequence of our result, we can rule out the existence
of electrostatic configurations involving multiple "very compact" electrically
charged bodies and sub-extremal black holes.Comment: 16 pages. This paper extends the photon sphere uniqueness result
obtained in arXiv:1504.05804 from the vacuum to the electro-vacuum setting.
While the general proof method is similar, a number of new nontrivial issues
aris
