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

We examine the quantum loop effects on the single-field inflationary models in a spatially flat Friedmann-Robertson-Walker 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 (SR) to ultra-slow-roll (USR) and SR-USR-SR inflation, in which it is shown that density perturbations originating from quantum vacuum fluctuations can be enhanced at small scales and then potentially collapse into primordial black holes. 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.