Gravitational particle creation for dark matter and reheating
  The purely gravitational dark matter (PGDM) which interacts with the standard
model particles only by gravitational interaction has recently been discussed.
Due to its feeble interaction, PGDM may be produced mainly by the gravitational
particle creation, which plays an important role in the reheating after
kinetically driven inflation and some potential-driven inflation without
subsequent inflaton oscillating phase. Therefore, we consider the possibility
of the gravitational reheating model which can also explain the present PGDM
density at the same time. We consider a model where two massive scalar fields
are incorporated into the standard model besides the inflation sector. We show
that the gravitational particle creation prevails over the thermal creation ---
the freeze-in process --- and it can actually explain the reheating and the
present abundance of dark matter if one of the scalar particles is as heavy as
the Hubble parameter during inflation $\sim10^{13}$ GeV and finally decays into
radiation via sufficiently weak coupling, and the other is a stable PGDM with
its mass of the order of $10^3$ GeV.
