Wormholes versus black holes: quasinormal ringing at early and late times

TL;DR

This paper investigates the quasinormal ringing of traversable wormholes, especially the Bronnikov-Ellis type, comparing their spectral features to black holes, and explores how asymmetry affects superradiance and observational distinguishability.

Contribution

It analyzes the quasinormal modes of non-thin-shell Bronnikov-Ellis wormholes and examines the effects of asymmetry on superradiance and black hole mimicry.

Findings

Wormholes can ring as black holes or differently depending on parameters.

Superradiance occurs only in non-symmetric wormholes with different rotation parameters.

Symmetric wormholes cannot mimic black hole ringing at multiple multipoles.

Abstract

Recently it has been argued that the phantom thin-shell wormholes matched with the Schwarzschild space-time near the Schwarzschild radius ring like Schwarzschild black holes at early times, but differently at late times (arXiv:1602.07309). Here we consider perturbations of the wormhole which was constructed without thin-shells: the Bronnikov-Ellis wormhole supported by the phantom matter and electromagnetic field. This wormhole solution is known to be stable under specific equation of state of the phantom matter. We show that if one does not use the above thin-shell matching, the wormhole, depending on the values of its parameters, either rings as the black hole at all times or rings differently also at all times. The wormhole's spectrum, investigated here, posses a number of distinctive features. In the final part we have considered general properties of scattering around arbitrary rotating traversable wormholes. We have found that symmetric and non-symmetric (with respect to the throat) wormholes are qualitatively different in this respect: First, superradiance is allowed only if for those non-symmetric wormholes for which the asymptotic values of the rotation parameters are different on both sides from the throat. Second, the symmetric wormholes cannot mimic effectively the ringing of a black hole at a few various dominant multipoles at the same time, so that the future observations of various events should easily tell the symmetric wormhole from a black hole.