Can Star-Disk Collisions Explain the Missing Red Giants Problem in the
  Galactic Center?
  Observations have revealed a relative paucity of red giant (RG) stars within
the central 0.5pc in the Galactic Center (GC). Motivated by this finding we
investigate the hypothesis that collisions of stars with a fragmenting
accretion disk are responsible for the observed dearth of evolved stars. We use
3-dimensional hydrodynamic simulations to model a star with radius $10
R_{\odot}$ and mass $1 M_{\odot}$, representative of the missing population of
RGs, colliding with high density clumps. We find that multiple collisions with
clumps of column density $\gtrsim10^{8}\, {\rm g\,cm^{-2}}$ can strip a
substantial fraction of the star's envelope and in principle render it
invisible to observations. Simulations confirm that repeated impacts are
particularly efficient in driving mass loss as partially stripped RGs expand
and have increased cross sections for subsequent collisions. Because the
envelope is unbound on account of the kinetic energy of the star, any
significant amount of stripping of the RG population in the GC should be
mirrored by a systematic decay of their orbits and possibly by their enhanced
rotational velocity. To be viable, this scenario requires that the total mass
of the fragmenting disk has been several orders of magnitude higher than that
of the early type stars which now form the stellar disk in the GC.
