Delocalization of brane gravity by a bulk black hole

TL;DR

This paper explores how the presence of a bulk black hole in a brane-world model affects gravity localization, showing that gravity becomes delocalized and is replaced by metastable modes, contrasting with the standard RS model.

Contribution

It demonstrates that a bulk black hole prevents stable gravity localization on the brane, introducing metastable quasinormal modes instead of a zero-mode, extending understanding of brane-world gravity.

Findings

No stable zero-mode in the presence of a bulk black hole

Gravity is delocalized by the 5D horizon

Existence of metastable quasinormal modes

Abstract

We investigate the analogue of the Randall-Sundrum brane-world in the case when the bulk contains a black hole. Instead of the static vacuum Minkowski brane of the RS model, we have an Einstein static vacuum brane. We find that the presence of the bulk black hole has a dramatic effect on the gravity that is felt by brane observers. In the RS model, the 5D graviton has a stable localized zero-mode that reproduces 4D gravity on the brane at low energies. With a bulk black hole, there is no such solution -- gravity is delocalized by the 5D horizon. However, the brane does support a discrete spectrum of metastable massive bound states, or quasinormal modes, as was recently shown to be the case in the RS scenario. These states should dominate the high frequency component of the bulk gravity wave spectrum on a cosmological brane. We expect our results to generalize to any bulk spacetime containing a Killing horizon.