Influence of large local and non-local bispectra on primordial black hole abundance

TL;DR

This paper investigates how different types of non-Gaussian bispectra influence primordial black hole abundance constraints, revealing that local and equilateral shapes significantly affect these constraints, unlike the orthogonal shape.

Contribution

It extends previous analyses by considering arbitrary magnitudes of various bispectrum shapes and their impact on primordial black hole constraints.

Findings

Skewness accurately estimates non-Gaussian effects on constraints.

Orthogonal bispectrum shape has a weaker impact compared to local and equilateral shapes.

Non-Gaussianity can significantly alter primordial black hole abundance constraints.

Abstract

Primordial black holes represent a unique probe to constrain the early universe on small scales - providing the only constraints on the primordial power spectrum on the majority of scales. However, these constraints are strongly dependent on even small amounts of non-Gaussianity, which is unconstrained on scales significantly smaller than those visible in the CMB. This paper goes beyond previous considerations to consider the effects of a bispectrum of the equilateral, orthogonal and local shapes with arbitrary magnitude upon the abundance of primordial black holes. Non-Gaussian density maps of the early universe are generated from a given bispectrum and used to place constraints on the small scale power spectrum. When small, we show that the skewness provides an accurate estimate for how the constraint depends on non-Gaussianity, independently of the shape of the bispectrum. We show that the orthogonal template of non-Gaussianity has an order of magnitude weaker effect on the constraints than the local and equilateral templates.