  Galactic nuclei should contain a cluster of stars and compact objects in the
vicinity of the central supermassive black hole due to stellar evolution, minor
mergers and gravitational dynamical friction. By analogy with protoplanetary
migration, nuclear cluster objects (NCOs) can migrate in the accretion disks
that power active galactic nuclei by exchanging angular momentum with disk gas.
Here we show that an individual NCO undergoing runaway outward migration
comparable to Type III protoplanetary migration can generate an accretion rate
corresponding to Seyfert AGN or quasar luminosities. Multiple migrating NCOs in
an AGN disk can dominate traditional viscous disk accretion and at large disk
radii, ensemble NCO migration and accretion could provide sufficient heating to
prevent the gravitational instability from consuming disk gas in star
formation. The magnitude and energy of the X-ray soft excess observed at
~0.1-1keV in Seyfert AGN could be explained by a small population of
~10^{2}-10^{3} accreting stellar mass black holes or a few ULXs. NCO migration
and accretion in AGN disks are therefore extremely important mechanisms to add
to realistic models of AGN disks.
