Gravitational Waves from Oscillon Preheating

TL;DR

This paper investigates the gravitational wave background generated during oscillon formation after inflation, revealing that the process imprints multiple peaks on the spectrum, despite individual oscillons not radiating gravitational waves.

Contribution

It demonstrates that the stochastic gravitational wave background from oscillon preheating has distinct spectral features linked to oscillon size, advancing understanding of early Universe signals.

Findings

Gravitational waves are mainly produced during oscillon formation, not from individual oscillons.

The gravitational wave spectrum exhibits multiple peaks corresponding to oscillon sizes.

Oscillon-dominated phases can leave detectable imprints in the gravitational wave background.

Abstract

Oscillons are long-lived, localized excitations of nonlinear scalar fields which may be copiously produced during preheating after inflation, leading to a possible oscillon-dominated phase in the early Universe. For example, this can happen after axion monodromy inflation, on which we run our simulations. We investigate the stochastic gravitational wave background associated with an oscillon-dominated phase. An isolated oscillon is spherically symmetric and does not radiate gravitational waves, and we show that the flux of gravitational radiation generated between oscillons is also small. However, a significant stochastic gravitational wave background may be generated during preheating itself (i.e, when oscillons are forming), and in this case the characteristic size of the oscillons is imprinted on the gravitational wave power spectrum, which has multiple, distinct peaks.