Wormholes as Black Hole Foils

TL;DR

Damour and Solodukhin investigate whether a globally static wormhole with a small parameter $\lambda$ can mimic many observational features of Schwarzschild black holes. By comparing geodesics, no-hair properties, QNM ringing, dissipative responses, and quantum throat modes, they show that several hallmark BH phenomena can be reproduced without an event horizon, provided $\lambda$ is exponentially small; Hawking radiation remains the principal, albeit impractical, discriminator. They also identify a spectrum of throat-bound quantum states that could encode information, drawing a loose parallel to black hole microstates. The work highlights that many aspects of black hole phenomenology do not strictly require horizons, offering a valuable conceptual foil for interpreting strong-gravity observations and the role of horizons in information puzzles.

Abstract

We study to what extent wormholes can mimic the observational features of black holes. It is surprisingly found that many features that could be thought of as ``characteristic'' of a black hole (endowed with an event horizon) can be closely mimicked by a globally static wormhole, having no event horizon. This is the case for: the apparently irreversible accretion of matter down a hole, no-hair properties, quasi-normal-mode ringing, and even the dissipative properties of black hole horizons, such as a finite surface resistivity equal to 377 Ohms. The only way to distinguish the two geometries on an observationally reasonable time scale would be through the detection of Hawking's radiation, which is, however, too weak to be of practical relevance for astrophysical black holes. We point out the existence of an interesting spectrum of quantum microstates trapped in the throat of a wormhole which could be relevant for storing the information ``lost'' during a gravitational collapse.