What can we learn from the stochastic gravitational wave background produced by oscillons?

TL;DR

This paper investigates how oscillons formed during preheating after inflation generate a distinctive stochastic gravitational wave background, revealing insights into early universe physics through semi-analytical and numerical methods.

Contribution

It introduces semi-analytical techniques to study GW production from oscillons and compares results with lattice simulations across different inflation models.

Findings

Good agreement between semi-analytical and numerical results.

Oscillon parameters significantly influence the GW spectrum.

Distinct spectral features can inform early universe physics.

Abstract

The stochastic gravitational wave (GW) background provides a fascinating window to the physics of the very early universe. Beyond the nearly scale-invariant primordial GW spectrum produced during inflation, a spectrum with a much richer structure is typically generated during the preheating phase after inflation (or after some other phase transition at lower energies). This raises the question of what one can learn from a future observation of the stochastic gravitational wave background spectrum about the underlying physics during preheating. Recently, it has been shown that during preheating non-perturbative quasi-stable objects like oscillons can act as strong sources for GW, leading to characteristic features such as distinct peaks in the spectrum. In this paper, we study the GW production from oscillons using semi-analytical techniques. In particular, we discuss how the GW spectrum is affected by the parameters that characterise a given oscillon system, e.g. by the background cosmology, the asymmetry of the oscillons and the evolution of the number density of the oscillons. We compare our semi-analytic results with numerical lattice simulations for a hilltop inflation model and a KKLT scenario, which differ strongly in some of these characteristics, and find very good agreement.