Enhanced Gravitational Waves from Inflaton Oscillons

TL;DR

This paper shows that oscillons formed after inflation can produce distinctive gravitational wave signals, which could be detected by future observatories, providing a new way to test inflationary models.

Contribution

It demonstrates that matter-dominance and decay of inflaton oscillons significantly enhance primordial gravitational waves, offering observable signatures independent of CMB constraints.

Findings

Oscillon-induced GWs are distinct and potentially detectable.

These GWs can be orders of magnitude lower in frequency than previous signals.

Detection prospects with Einstein Telescope, Cosmic Explorer, and DECIGO are promising.

Abstract

In broad classes of inflationary models the period of accelerated expansion is followed by fragmentation of the inflaton scalar field into localized, long-lived and massive oscillon excitations. We demonstrate that matter-dominance of oscillons, followed by their rapid decay, significantly enhances the primordial gravitational wave (GW) spectrum. These oscillon-induced GWs, sourced by second-order perturbations, are distinct and could be orders of magnitude lower in frequency than the previously considered GWs associated with oscillon formation. We show that detectable oscillon-induced GW signatures establish direct tests independent from cosmic microwave background radiation (CMB) for regions of parameter space of monodromy, logarithmic and pure natural (plateau) potential classes of inflationary models, among others. We demonstrate that oscillon-induced GWs in a model based on pure natural inflation could be directly observable with the Einstein Telescope, Cosmic Explorer and DECIGO. These signatures offer a new route for probing the underlying inflationary physics.