Ergoregion instability and echoes for braneworld black holes: Scalar, electromagnetic and gravitational perturbations

Understand

In the context of higher dimensional braneworld scenario, we have argued that the occurrence of horizonless exotic compact objects, as an alternative to classical black holes, are more natural.

• These exotic compact objects carry a distinctive signature of the higher dimension, namely a tidal charge parameter, inherited from the projection of the higher dimensional Weyl tensor onto the four dimensional spacetime we live in.
• Due to the absence of any horizon, rotating exotic compact objects are often unstable because of superradiance.
• Interestingly, these higher dimensional exotic compact objects, in the presence of the tidal charge, are more stable than their four dimensional counterpart.