Black Hole Spindown by Light Bosons
  The saturation mechanism for the fastest-growing instability of massive scalar field in Kerr metric is identified, assuming saturation by cubic or quartic nonlinearities of the field potential. The resulting spindown rate of the black hole is calculated. The (rather involved) saturation scenario is confirmed by numerical simulations. 
Andrei Gruzinov
astro-ph.HE gr-qc hep-ph