Primordial Black Hole Formation in Non-Minimal Curvaton Scenario
  In the curvaton scenario, the curvature perturbation is generated after
inflation at the curvaton decay, which may have a prominent non-Gaussian
effect. For a model with a non-trivial kinetic term, an enhanced curvature
perturbation on a small scale can be realized, which can lead to copious
production of primordial black holes (PBHs) and induce secondary gravitational
waves (GWs). Using the probability distribution function which takes full
nonlinear effects into account, we calculate the PBH formation. We find that
under the assumption that thus formed PBHs would not overclose the universe,
the non-Gaussianity of the curvature perturbation can be well approximated by
the local quadratic form, which can be used to calculate the induced GWs. In
this model the limit of large non-Gaussianity can be reached when the curvaton
energy fraction $r$ is small at the moment of curvaton decay. We also show that
the $r\to1$ limit of non-Gaussianity coincides with that of ultra-slow-roll
inflation.
