2025/02/14 by Hassan Firouzjahi, Firouzjahi, Hassan, Bahar Nikbakht +1 · 7 citations
Physics and Astronomy · #Atomic and Molecular Physics #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Phenomenology (hep-ph) #High Energy Physics - Theory (hep-th) #High-Energy Particle Collisions Research #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2502.10287
openalex publication_date 2025/02/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We calculate the action and the interaction Hamiltonians to all orders in perturbation theory in the model of single field inflation with a transient ultra slow-roll phase. Employing the formalism of EFT of inflation, we obtain a compact non-perturbative expression for the interaction Hamiltonian in terms of the Goldstone field π in the decoupling limit. In addition, we also present a non-linear relation between π and the curvature perturbations to all orders in perturbation theory. These are powerful results which enable us to calculate the cosmological correlators and loop corrections to any order in perturbation theory. As a non-trivial example, we calculate the L-loop corrections on long CMB scale perturbations in the USR models which are used for PBHs formation. We show that the loop corrections scale like (ΔN \cal Pe L) L in which \cal Pe is the peak of the power spectrum and ΔN is the duration of the USR phase. This indicates that the loop corrections grow quickly out of perturbative control for large values of L. In the conventional USR setup for PBHs formation with ΔN ≃ 2.5, this happens at L=4.