Hidden Dark Matter from Starobinsky Inflation
  The Starobinsky inflation model is one of the simplest inflation models that
is consistent with the cosmic microwave background observations. In order to
explain dark matter of the universe, we consider a minimal extension of the
Starobinsky inflation model with introducing the dark sector which communicates
with the visible sector only via the gravitational interaction. In Starobinsky
inflation model, a sizable amount of dark-sector particle may be produced by
the inflaton decay. Thus, a scalar, a fermion or a vector boson in the dark
sector may become dark matter. We pay particular attention to the case with
dark non-Abelian gauge interaction to make a dark glueball a dark matter
candidate. In the minimal setup, we show that it is difficult to explain the
observed dark matter abundance without conflicting observational constraints on
the coldness and the self-interaction of dark matter. We propose scenarios in
which the dark glueball, as well as other dark-sector particles, from the
inflaton decay become viable dark matter candidates. We also discuss
possibilities to test such scenarios.
