Ruling Out Primordial Black Hole Formation From Single-Field Inflation

Jason Kristiano and Jun'ichi Yokoyama

Submitted on 7 November 2022


The most widely studied formation mechanism of a primordial black hole (PBH) is collapse of large-amplitude perturbation on small scales generated in single-field inflation. In this Letter, we calculate one-loop correction to the large-scale power spectrum in such a model. We find models producing appreciable amount of PBHs generically induce too large one-loop correction on large scale probed by cosmic microwave background radiation. We therefore conclude that PBH formation from single-field inflation is ruled out.


Subjects: High Energy Physics - Theory; Astrophysics - Cosmology and Nongalactic Astrophysics


Schematic picture of the inflaton potential realizing PBH formation. When the inflaton is around $\phi_\mathrm{CMB}$, scales probed by CMB observations leave horizon and it is in the SR regime. It enters an extremely flat region at $t=t_s$  undergoing an USR period. It enters SR period again at $t=t_e$ until $\phi_\mathrm{end}$, the end of inflation.