Universal Gravitational Waves from Interacting and Clustered Solitons

TL;DR

This paper explores how interactions and clustering of primordial solitons like oscillons and Q-balls can significantly enhance the universal gravitational wave background, providing new observational probes of early Universe physics.

Contribution

It demonstrates that soliton interactions and clustering can amplify gravitational wave signals, expanding the potential for early Universe studies with upcoming GW detectors.

Findings

Soliton interactions increase GW background amplitude.

Clustering of solitons leads to correlated density fields.

Enhanced GW signals can probe early Universe physics.

Abstract

Causal soliton formation (e.g. oscillons, Q-balls) in the primordial Universe is expected to give rise to a universal gravitational wave (GW) background, at frequencies smaller than scales of nonlinearity. We show that modifications of the soliton density field, driven by soliton interactions or initial conditions, can significantly enhance universal GWs. Gravitational clustering of solitons naturally leads to generation of correlations in the large-scale soliton density field. As we demonstrate for axion-like particle (ALP) oscillons, the growing power spectrum amplifies universal GW signals, opening new avenues for probing the physics of the early Universe with upcoming GW experiments. Our results are applicable to variety of scenarios, such as solitons interacting through a long range Yukawa-like fifth force.