Generating PBHs and small-scale GWs in two-field models of inflation
  Primordial black holes (PBHs) generated by gravitational collapse of large
primordial overdensities can be a fraction of the observed dark matter. In this
paper, we introduce a mechanism to produce a large peak in the primordial power
spectrum (PPS) in two-field inflationary models characterized by two stages of
inflation based on a large non-canonical kinetic coupling. This mechanism is
generic to several two-field inflationary models, due to a temporary tachyonic
instability of the isocurvature perturbations at the transition between the two
stages of inflation. We numerically compute the primordial perturbations from
largest scales to the small scales corresponding to that of PBHs using an
extension of BINGO (BI-spectra and Non-Gaussianity Operator). Moreover we
numerically compute the stochastic background of gravitational waves (SBGW)
produced by second order scalar perturbations within frequencies ranging from
nano-Hz to KHz that covers the observational scales corresponding to Pulsar
Timing Arrays, Square Kilometer Array to that of Einstein telescope. We discuss
the prospect of its detection by these proposed and upcoming gravitational
waves experiments.
