Scalar cosmological perturbations from inflationary black holes

TL;DR

This paper investigates how small black holes formed before inflation could alter the scalar power spectrum in the early universe, potentially providing observable signatures to test cosmological models.

Contribution

It derives the correction to the scalar power spectrum caused by pre-inflationary black holes using the Keldysh propagator in Schwarzschild-de Sitter space, a novel approach.

Findings

Black holes can significantly modify the scalar power spectrum.

The correction might be detectable with current or future observations.

The effect could potentially rule out certain pre-inflationary scenarios.

Abstract

We study the correction to the scale invariant power spectrum of a scalar field on de Sitter space from small black holes that formed during a pre-inflationary matter dominated era. The formation probability of such black holes is estimated from primordial Gaussian density fluctuations. We determine the correction to the spectrum by first deriving the Keldysh propagator for a massless scalar field on Schwarzschild-de Sitter space. Our results suggest that the effect is strong enough to be tested -- and possibly even ruled out -- by observations.