On stellar-mass black hole mergers in AGN disks detectable with LIGO
  Black hole mergers detectable with LIGO can occur in active galactic nucleus
(AGN) disks. Here we parameterize the merger rates, the mass spectrum and the
spin spectrum of black holes (BH) in AGN disks. The predicted merger rate spans
$\sim 10^{-4}-10^{4} \rm{Gpc}^{-1} \rm{yr}^{-1}$, so upper limits from LIGO
($<212\rm{Gpc}^{-1}\rm{yr}^{-1}$) already constrain it. The predicted mass
spectrum has the form of a broken power-law consisting of a pre-existing BH
powerlaw mass spectrum and a harder powerlaw mass spectrum resulting from
mergers. The predicted spin spectrum is multi-peaked with the evolution of
retrograde spin BH in the gas disk playing a key role. We outline the large
uncertainties in each of these LIGO observables for this channel and we discuss
ways in which they can be constrained in the future.
