Stochastic gravitational-wave background from spin loss of black holes

Understand

Although spinning black holes are shown to be stable in vacuum in general relativity, there exists exotic mechanisms that can convert the spin energy of black holes into gravitational waves.

• Such waves may be very weak in amplitude, since the spin-down could take a long time, and a direct search may not be feasible.
• We propose to search for the stochastic background associated with the spin-down, and we relate the level of this background to the formation rate of spinning black holes from the merger of binary black holes, as well as the energy spectrum of waves emitted by the spin-down process.
• We argue that current LIGO-Virgo observations are not inconsistent with the existence of a spin-down process, as long as it is slow enough.