Non-Gaussianity from the Cross-correlation of the Astrophysical Gravitational Wave Background and the Cosmic Microwave Background

TL;DR

This paper investigates how cross-correlating the astrophysical gravitational wave background with the CMB can reveal primordial non-Gaussianity, using future space-based detectors to assess detection prospects.

Contribution

It introduces a novel method to probe primordial non-Gaussianity through the cross-correlation of GW and CMB anisotropies, highlighting the potential of next-generation detectors.

Findings

Cross-correlation is sensitive to primordial non-Gaussianity.

Next-generation detectors can potentially detect the cross-correlation signal.

Constraints on primordial non-Gaussianity can be improved through this method.

Abstract

Since the first LIGO/Virgo detection, Gravitational Waves (GWs) have been very promising as a new complementary probe to understand our Universe. One of the next challenges of GW search is the detection and characterization of the stochastic gravitational wave background (SGWB), that is expected to open a window on the very early Universe (cosmological background) and to provide us new information on astrophysical source populations (astrophysical background). One way to characterize the SGWB and to extract information about its origin is through the cross-correlation with other cosmological probes. To this aim, in this paper, we explore the cross-correlation between the astrophysical background anisotropies and the Cosmic Microwave Background (CMB) ones. Such a signal is sensitive to primordial non-Gaussianity (nG) through the GW bias. Thus, we study the capability of next generation space-based interferometers to detect such a cross-correlation signal and to constrain primordial nG.