Dynamical Properties of Eccentric Nuclear Disks: Stability, Longevity,
  and Implications for Tidal Disruption Rates in Post-Merger Galaxies
  In some galaxies, the stars orbiting the supermassive black hole take the
form of an eccentric nuclear disk, in which every star is on a coherent,
apsidally-aligned orbit. The most famous example of an eccentric nuclear disk
is the double nucleus of Andromeda, and there is strong evidence for many more
in the local universe. Despite their apparent ubiquity however, a dynamical
explanation for their longevity has remained a mystery: differential precession
should wipe out large-scale apsidal-alignment on a short timescale. Here we
identify a new dynamical mechanism which stabilizes eccentric nuclear disks,
and explain for first time the negative eccentricity gradient seen in the
Andromeda nucleus. The stabilizing mechanism drives oscillations of the
eccentricity vectors of individual orbits, both in direction (about the mean
body of the disk) and in magnitude. Combined with the negative eccentricity
gradient, the eccentricity oscillations push some stars near the inner edge of
the disk extremely close to the black hole, potentially leading to tidal
disruption events. Order of magnitude calculations predict extremely high rates
in recently-formed eccentric nuclear disks ($\sim0.1 - 1$ ${\rm yr}^{-1} {\rm
gal}^{-1}$). Unless the stellar disks are replenished, these rates should
decrease with time as the disk depletes in mass. If eccentric nuclear disks
form during gas-rich major mergers, this may explain the preferential
occurrence of tidal disruption events in recently-merged and post-merger
(E+A/K+A) galaxies.
