Any negative value of the second slow-roll parameter can amplify the scalar power spectrum through sub-horizon growth, so the usual ultra-slow-roll requirement of epsilon2 <= -6 is not necessary.
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Sub-Horizon Amplification of Curvature Perturbations: A New Route to Primordial Black Holes and Gravitational Waves
Any negative value of the second slow-roll parameter can amplify the scalar power spectrum through sub-horizon growth, so the usual ultra-slow-roll requirement of epsilon2 <= -6 is not necessary.