Black Hole Portal into Hidden Valleys

TL;DR

This paper explores how superradiant instabilities in rotating black holes coupled with a hidden gauge sector can induce phase transitions, releasing energy as electromagnetic bursts with specific frequencies.

Contribution

It introduces a novel mechanism where black hole superradiance causes a hidden sector phase transition, leading to observable electromagnetic signals.

Findings

Black hole superradiance can trigger hidden sector phase transitions.

Significant energy release as hidden mesons can produce electromagnetic bursts.

Burst frequencies range from 100 eV to 100 MeV.

Abstract

Superradiant instability turns rotating astrophysical black holes into unique probes of light axions. We consider what happens when a light axion is coupled to a strongly coupled hidden gauge sector. In this case superradiance results in an adiabatic increase of a hidden sector CP-violating $\theta$-parameter in a near horizon region. This may trigger a first order phase transition in the gauge sector. As a result a significant fraction of a black hole mass is released as a cloud of hidden mesons and can be later converted into electromagnetic radiation. This results in a violent electromagnetic burst. The characteristic frequency of such bursts may range approximately from 100 eV to 100 MeV.