Do the Spirits Rise?
  A nonlocal gravity model based on $\frac1{\square} R$ achieves the
phenomenological goals of generating cosmic acceleration without dark energy
and of suppressing the growth of perturbations compared to the $\Lambda$CDM
model. Although the localized version of this model possesses a scalar ghost,
the nonlocal version does not suffer from any obvious problem with ghosts. Here
we study the possibility that the scalar ghost mode might be excited through
time evolution, even though it is initially absent. We present strong evidence
that this does not happen.
