The Origin and Detection of High-Redshift Supermassive Black Holes
  Supermassive black holes (SMBHs) are common in local galactic nuclei, and
SMBHs as massive as several billion solar masses already exist at redshift z=6.
These earliest SMBHs may arise by the combination of Eddington-limited growth
and mergers of stellar-mass seed BHs left behind by the first generation of
metal-free stars, or by the rapid direct collapse of gas in rare special
environments where the gas can avoid fragmenting into stars. In this
contribution, I review these two competing scenarios. I also briefly mention
some more exotic ideas and how the different models may be distinguished in the
future by LISA and other instruments.
