Space missions to detect the cosmic gravitational-wave background

TL;DR

Detecting the cosmic gravitational-wave background (CGB) could reveal insights about the universe's formation, but requires advanced space-based interferometers and careful analysis of weak signals amidst astrophysical foregrounds.

Contribution

We developed a general formalism for calculating detector responses applicable to any configuration, aiding the design of future space-based interferometers for CGB detection.

Findings

A coordinate-free formalism for detector response

Identification of promising GABI mission designs

Detection of CGB is feasible with current technology

Abstract

It is thought that a stochastic background of gravitational waves was produced during the formation of the universe. A great deal could be learned by measuring this Cosmic Gravitational-wave Background (CGB), but detecting the CGB presents a significant technological challenge. The signal strength is expected to be extremely weak, and there will be competition from unresolved astrophysical foregrounds such as white dwarf binaries. Our goal is to identify the most promising approach to detect the CGB. We study the sensitivities that can be reached using both individual, and cross-correlated pairs of space based interferometers. Our main result is a general, coordinate free formalism for calculating the detector response that applies to arbitrary detector configurations. We use this general formalism to identify some promising designs for a GrAvitational Background Interferometer (GABI) mission. Our conclusion is that detecting the CGB is not out of reach.