Constraining the inflaton potential with gravitational waves from oscillons

TL;DR

This paper demonstrates how gravitational waves produced by oscillons formed after inflation can be used to constrain inflaton properties, offering new insights beyond traditional CMB observations.

Contribution

It introduces a novel method to constrain inflaton parameters using gravitational wave signals from oscillon decay, complementing existing observational techniques.

Findings

Enhanced gravitational wave production from oscillon decay saturates observational bounds.

Constraints on inflaton mass and self-couplings derived from gravitational wave data.

Provides new parameter space constraints inaccessible to CMB measurements.

Abstract

Under certain conditions, the oscillating inflaton condensate filling the Universe after inflation can fragment and form so-called oscillons. These long-lived soliton-like field configurations can dominate the Universe for several $e$-folds of expansion, leading to an early matter-dominated phase preceding the standard radiation era. In this paper we show how the rapid final decay of the oscillons leads to an enhanced production of induced gravitational waves, whose energy density can saturate the observational bound on the effective number of relativistic species. We leverage this bound to constrain the inflaton mass, cubic, and quartic self-coupling in generic models that admit oscillon formation, providing novel and complementary constraints in regions of parameter space that are inaccessible with cosmic microwave background observations alone.