Primordial black holes from sound speed resonance in the
  inflaton-curvaton mixed scenario
  We study sound speed resonance (SSR) mechanism for primordial black hole
(PBH) formation in an early universe scenario with inflaton and curvaton being
mixed. In this scenario, the total primordial density perturbations can be
contributed by the fluctuations from both the inflaton and curvaton fields, in
which the inflaton fluctuations lead to the standard adiabatic perturbations,
while the sound speed of the curvaton fluctuations are assumed to be
oscillating during inflation. Due to the narrow resonance effect of SSR
mechanism, we acquire the enhanced primordial density perturbations on small
scales and it remains nearly scale-invariant on large scales, which is
essential for PBH formation. Finally, we find that the PBHs with specific mass
spectrum can be produced with a sufficient abundance for dark matter in the
mixed scenario.
