Primordial Non-Gaussianity in Models with Dark Matter Isocurvature
  Fluctuations
  We investigate primordial non-Gaussianity and dark matter isocurvature
fluctuations in the modulated reheating and the curvaton scenarios. In these
scenarios, large non-Gaussianity can be generated, on the other hand, depending
on how dark matter is produced, too large isocurvature fluctuations can also
arise, which is inconsistent with current observations. In this paper, we study
this issue in a mixed scenario where the curvature fluctuations can also be
produced from the inflaton fluctuations as well as those from a light scalar
field such as the modulus and the curvaton. We show that primordial
fluctuations can be highly non-Gaussian without conflicting the current
constraint on isocurvature fluctuations for such mixed scenarios. However, if
the constraint on isocurvature fluctuations becomes severer as expected by the
Planck satellite, $f_{\rm NL}$, a nonlinearity parameter for adiabatic
fluctuations, should be very small as $f_{\rm NL} \lesssim 3$, which would give
interesting implications for the generation mechanism of dark matter.
Non-Gaussianity from isocurvature fluctuations is also discussed in these
scenarios.
