Quantum loop effects to the power spectrum of primordial perturbations during ultra slow-roll inflation

Abstract

We examine the quantum loop effects on the single-field inflationary models in a spatially flat Friedmann-Robertson-Walker (FRW) cosmological space-time with a general self-interacting scalar field potential, which is modeled in terms of the Hubble flow parameters in the effective field theory approach. In particular, we focus on the scenarios in both slow-roll to ultra-slow-roll (SR-USR) and SR-USR-SR inflation, in which it is shown that density perturbations originated from quantum vacuum fluctuations can be enhanced at small-scales, and then potentially collapse into primordial black holes (PBHs). Here our estimates indicate significant one-loop corrections around the peak of the density power spectrum in both scenarios. The induced large quantum loop effects should be confirmed by a more formal quantum field theory, and, if so, should be treated in a self-consistent manner that will be discussed.