Black Hole Portal into Hidden Valleys

Understand

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.