Year: 2024
Type: article
Abstract: We discuss the issue of perturbativity in single-field inflationary models with a phase of ultraslow-roll (USR) tailor suited to generate an order-one abundance of primordial black holes (PBHs). More in detail, we impose the condition that loop corrections made up of short-wavelength modes enhanced by the USR dynamics do not alter the tree-level power spectrum of curvature perturbations. In our analysis, the USR phase is preceded and followed by two stages of ordinary slow-roll (SR), and we model the resulting SR/USR/SR dynamics using both instantaneous and smooth transitions. Focusing on scales relevant for cosmic microwave background observations, we find that it is not possible, with these arguments, to rule out the scenario of PBH formation via USR, not even in the limit of instantaneous transition. However, we also find that loop corrections of short modes on the power spectrum of long modes, even though not large enough to violate perturbativity requirements, remain appreciable and, most importantly, are not tamed in realistic realizations of smooth SR/USR/SR transitions. This makes perturbativity a powerful theoretical tool to constrain USR dynamics. We extend the analysis at any scale beyond those relevant for cosmic microwave background observations. We find that loop corrections of short modes remain within the few percent if compared to the tree-level power spectrum. However, we also find one notable exception of phenomenological relevance: we show that the so-called dip in the power spectrum of curvature perturbation is significantly reduced beyond the tree-level computation.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: Strong, Istituto Nazionale di Fisica Nucleare Sezione di Padova, European Commission, Ministero dell’Istruzione, dell’Università e della Ricerca, Istituto Nazionale di Fisica Nucleare, Horizon 2020 Framework Programme, Amaldi Research Center, H2020 European Research Council, HORIZON EUROPE Marie Sklodowska-Curie Actions
OpenAlex ID: W4400115032