Digging deeper: Observing primordial gravitational waves below the binary black hole produced stochastic background

TL;DR

This paper discusses how future ground-based gravitational wave detectors could distinguish primordial gravitational waves from the background created by black hole mergers, enabling detection of very faint signals.

Contribution

It demonstrates that next-generation detectors can subtract the black hole merger background to observe primordial gravitational waves at very low energy densities.

Findings

Next-generation detectors can observe black hole mergers across the universe.

Confusion background can be subtracted to reveal primordial signals.

Primordial background detection possible at $\, ext{Ω}_ ext{GW} \,\simeq 10^{-13}$ after five years.

Abstract

The merger rate of black hole binaries inferred from the detections in the first Advanced LIGO science run, implies that a stochastic background produced by a cosmological population of mergers will likely mask the primordial gravitational-wave background. Here we demonstrate that the next generation of ground-based detectors, such as the Einstein Telescope and Cosmic Explorer, will be able to observe binary black hole mergers throughout the universe with sufficient efficiency that the confusion background can potentially be subtracted to observe the primordial background at the level of $\Omega_{\mathrm{GW}} \simeq 10^{-13}$ after five years of observation.