Uniqueness of static vacuum asymptotically flat black holes and equipotential photon surfaces in n+1 dimensions \`a la Robinson

In this paper, we generalize to higher dimensions Robinson's approach to proving the uniqueness of connected (3+1) -dimensional static vacuum asymptotically flat black hole spacetimes. In consequence, we prove geometric inequalities for connected (n+1) -dimensional static vacuum asymptotically flat black holes, recovering results by Agostiniani and Mazzieri. We also obtain similar geometric inequalities for connected (n+1) -dimensional static vacuum asymptotically flat equipotential photon surfaces and in particular photon spheres. Assuming a natural upper bound on the total scalar curvature, we recover the well-known uniqueness results for such black holes and equipotential photon surfaces. We also extend the known equipotential photon surface uniqueness results to spacetimes with negative mass. In order to replace the role of the Cotton tensor in Robinson's proof, we introduce techniques inspired by the analysis of Ricci solitons.