Production of gravitational waves during preheating in the Starobinsky inflationary model

TL;DR

This paper investigates gravitational wave production during preheating in the Starobinsky inflation model with a nonminimal scalar field, revealing how the coupling parameter influences the GW spectrum and its observational constraints.

Contribution

It provides the first lattice simulation analysis of GW production in the Starobinsky model with a nonminimally coupled scalar field, highlighting the impact of the coupling parameter on GW spectra.

Findings

GW spectrum grows rapidly with increasing |ξ|

Maximum GW amplitude occurs at specific negative and positive ξ values

Produced GWs are consistent with current and future CMB observational limits

Abstract

The production of GWs during preheating in the Starobinsky model with a nonminimally coupled auxiliary scalar field is studied through the lattice simulation in this paper. We find that the GW spectrum $\Omega_{\rm gw}$ grows fast with the increase of the absolute value of coupling parameter $\xi$. This is because the resonant bands become broad with the increase of $|\xi|$. When $\xi<0$, $\Omega_{\rm gw}$ begins to grow once the inflation ends and grows faster than the case of $\xi>0$. $\Omega_{\rm gw}$ reaches the maximum at $\xi=-20$ ($\xi=42$ for the case $\xi>0$) and then decreases with slight oscillation. Furthermore we find that the GWs produced in the era of preheating satisfy the limits from the Planck and next-generation CMB experiments.