Non-Perturbative Hamiltonian and Higher Loop Corrections in USR Inflation
This paper utilizes the EFT of inflation in the decoupling limit to derive a non-perturbative Hamiltonian for single-field ultra slow-roll (USR) inflation, revealing that instantaneous transitions to the slow-roll phase cause higher-order loop corrections on long CMB scales to grow rapidly, potentially pushing the model out of perturbative control.