Non-perturbative non-Gaussianity and primordial black holes

We present a non-perturbative method for calculating the abundance of primordial black holes given an arbitrary one-point probability distribution function for the primordial curvature perturbation, P(ζ). A non-perturbative method is essential when considering nonGaussianities that cannot be treated using a conventional perturbative expansion. To determine the full statistics of the density field, we relate ζ to a Gaussian field by equating the cumulative distribution functions. We consider two examples: a specific local-type non-Gaussian distribution arising from ultra slow roll models, and a general piecewise model for P(ζ) with an exponential tail. We demonstrate that the enhancement of primordial black hole formation is due to the intermediate regime, rather than the far tail. We also show that non-Gaussianity can have a significant impact on the shape of the primordial black hole mass distribution.