Primordial Black Holes from Inflation with a Spectator Field
The study investigates adding a spectator field to single-field inflation models featuring ultra-slow roll (USR) evolution to see its effect on primordial black hole (PBH) production. The inclusion of this field maintains or enhances PBH production, despite changing the background dynamics. This enhancement occurs by replacing USR with a transient tachyonic instability and subsequent power transfer to curvature perturbations, while remaining consistent with CMB observations.