Over the horizon: distinguishing the Schwarzschild spacetime and the ${\mathbb{RP}}^3$ spacetime using an Unruh-DeWitt detector

Keith K. Ng, Robert B. Mann, Eduardo Martin-Martinez

We show that a particle detector can distinguish the ${\mathbb{RP}}^3$ geon from the Schwarzschild black hole, even though they differ only by a topological identification beyond the…