Nonlocal star as a blackhole mimicker
  In the context of ghost-free, infinite derivative gravity, we will provide a
quantum mechanical framework in which we can describe astrophysical objects
devoid of curvature singularity and event horizon. In order to avoid ghosts and
singularity, the gravitational interaction has to be nonlocal, therefore, we
call these objects as nonlocal stars. Quantum mechanically a nonlocal star is a
self-gravitational bound system of many gravitons interacting nonlocally.
Outside the nonlocal star the spacetime is well described by the Schwarzschild
metric, while inside we have a non-vacuum spacetime metric which tends to be
conformally flat at the origin. Remarkably, in the most compact scenario the
radius of a nonlocal star is of the same order of the Buchdahl limit, therefore
slightly larger than the Schwarzschild radius, such that there can exist a
photosphere. These objects live longer than a Schwarzschild blackhole and they
are very good absorbers, due to the fact that the number of available states is
larger than that of a blackhole. As a result nonlocal stars, not only can be
excellent blackhole mimickers, but can also be considered as dark matter
candidates. In particular, nonlocal stars with masses below $10^{14}$g can be
made stable compared to the age of the Universe.
