If fluctuations from inflation on relevant scales reach an amplitude of order one, they can serve as a precursor for the formation of primordial black holes (PBHs), once they reenter the horizon after inflation. Most of the inflationary scenarios that try to accommodate such enhancement mechanisms, run into difficulties with the Effective Field Theory (EFT) criteria. In this talk, I unravel a new mechanism of enhancing the power spectrum during inflation, which is based on this observation in the formalism of Extended EFT of inflation (EEFToI) with the sixth order polynomial dispersion relation, that if the quartic coefficient in the dispersion relation is negative and smaller than a threshold, the amplitude of the power spectrum can be enhanced substantially. The instability mechanism needs to be arranged to kick in at the scales of interest which is related to the mass of the PBHs one would like to produce. This can be accommodated within the EEFToI by endowing timedependence to the coefficients of the dispersion relation, or in turn, to the couplings in the unitary gauge action. We argue that for the range of parameters that the mechanism enhances the amplitude of the power spectrum with the required amount, the EFT criteria are well respected. The mechanism can be used to produce PBHs in various mass ranges, including tens of solar mass PBHs, which are useful to explain the LIGO events, or 10^1310^17 solar mass, which can comprise the whole dark matter energy density.
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