Primordial black holes in excursion set theory: Formation probabilities, mass functions, and window functions

TL;DR

This paper analyzes how different window functions and correlated noises in excursion-set theory influence the formation probabilities and mass functions of primordial black holes, highlighting deviations from Carr's formula especially at low masses.

Contribution

It introduces a detailed study of PBH mass functions considering colored noises and various window functions within excursion-set theory, revealing deviations from traditional formulas.

Findings

Low-mass tail of the mass function differs from Carr's formula.

Correlated noises affect the degeneracy of formation probabilities.

Carr's formula remains practical near the characteristic mass with smooth Fourier window functions.

Abstract

We study the mass function of primordial black holes (PBHs) within the excursion-set theory, in which the response of the stochastic density contrast to the variation of the coarse-graining scale is described by colored noises. For several window functions often used in the literature, we investigate how this choice affects the formation probability as well as the resultant mass function of PBHs. It is found that the low-mass tail of the mass function differs from the one predicted from Carr's formula. The difference comes from the prevalence of correlated noises, by which degeneracy of the formation probabilities ceases to exist. Nevertheless, Carr's formula still provides a practical estimation in the vicinity of the characteristic mass scale, as long as a smooth window function in Fourier space is used.