Uniqueness of equipotential photon surfaces in 4-dimensional static vacuum asymptotically flat spacetimes for positive, negative, and zero mass -- and a new partial proof of the Willmore inequality

Carla Cederbaum, Albachiara Cogo, Axel Fehrenbach

We present different proofs of the uniqueness of 4-dimensional static vacuum asymptotically flat spacetimes containing a connected equipotential photon surface or in particular a c…