Gravitational Waves from Density Perturbations in an Early Matter Domination Era

TL;DR

This paper calculates the gravitational wave background generated by density perturbations during an early matter domination era, which could be detectable by future gravitational wave observatories.

Contribution

It introduces a novel calculation of gravitational waves produced from non-linear density perturbations leading to primordial black holes in an early matter era.

Findings

Gravitational wave background from early matter era perturbations is potentially detectable.

Black hole formation from perturbations produces a stochastic gravitational wave signal.

Asymmetrical collapse of matter generates a measurable gravitational wave imprint.

Abstract

We calculate the gravitational wave background produced from density perturbations in an early matter domination era where primordial black holes form. The formation of black holes requires perturbations out of the linear regime. Space with such perturbations reach a maximum expansion before it collapses asymmetrically forming a Zel'dovich pancake which depending on the parameters can either lead to a black hole or a virialized halo. In both cases and due to the asymmetry of the collapsing matter, a quadrupole moment generates gravitational waves which leave an imprint in the form of a stochastic background that can be detectable by near future gravitational interferometers.