How well do we know the primordial black hole abundance? The crucial role of nonlinearities when approaching the horizon

TL;DR

This paper examines how nonlinear effects in radiation transfer and horizon crossing calculations impact primordial black hole abundance estimates, suggesting current methods may overestimate their numbers and affect related gravitational wave interpretations.

Contribution

It highlights the importance of nonlinear corrections in primordial black hole abundance calculations and questions the reliability of standard estimation techniques.

Findings

Nonlinear corrections significantly affect PBH abundance estimates.

Current methods may overpredict the number of primordial black holes.

Implications for interpreting pulsar timing array data are discussed.

Abstract

We discuss the non-linear corrections entering in the calculation of the primordial black hole abundance from the non-linear radiation transfer function and the determination of the true physical horizon crossing. We show that the current standard techniques to calculate the abundance of primordial black holes suffer from uncertainties and argue that the primordial black hole abundance may be much smaller than what routinely considered. This would imply, among other consequences, that the interpretation of the recent pulsar timing arrays data from scalar-induced gravitational waves may not be ruled out because of an overproduction of primordial black holes.