Primordial Anisotropies in the Gravitational Wave Background from Cosmological Phase Transitions

TL;DR

This paper demonstrates that gravitational wave backgrounds from early universe phase transitions inherently possess anisotropies similar to the CMB, which can be detected and used to probe primordial physics and hidden sectors.

Contribution

It establishes the existence of anisotropies in gravitational wave backgrounds from phase transitions and discusses their potential for revealing new physics.

Findings

Gravitational wave backgrounds from phase transitions have anisotropies.

These anisotropies can be correlated with CMB data.

Detection of these anisotropies can inform about early universe physics.

Abstract

Phase transitions in the early universe can readily create an observable stochastic gravitational wave background. We show that such a background necessarily contains anisotropies analogous to those of the cosmic microwave background (CMB) of photons, and that these too may be within reach of proposed gravitational wave detectors. Correlations within the gravitational wave anisotropies and their cross-correlations with the CMB can provide new insights into the mechanism underlying primordial fluctuations, such as multi-field inflation, as well as reveal the existence of non-standard ``hidden sectors" of particle physics in earlier eras.