Gravitational Waves From the End of Inflation: Computational Strategies

TL;DR

This paper develops a numerical method to compute the gravitational wave spectrum produced during the post-inflationary preheating phase in various inflationary models, including hybrid models with inverted potentials.

Contribution

It introduces a computational algorithm for calculating gravitational wave spectra from preheating in scalar-field inflation models, including novel hybrid models with short, intense resonance periods.

Findings

Hybrid models with inverted potentials produce similar gravitational wave spectra as other models.

The algorithm effectively computes the gravitational wave background for different inflationary scenarios.

Preheating can generate a significant stochastic gravitational wave background.

Abstract

Parametric resonance or preheating is a plausible mechanism for bringing about the transition between the inflationary phase and a hot, radiation dominated universe. This epoch results in the rapid production of heavy particles far from thermal equilibrium and could source a significant stochastic background of gravitational radiation. Here, we present a numerical algorithm for computing the contemporary power spectrum of gravity waves generated in this post-inflationary phase transition for a large class of scalar-field driven inflationary models. We explicitly calculate this spectrum for both quartic and quadratic models of chaotic inflation, and low-scale hybrid models. In particular, we consider hybrid models with an ``inverted'' potential. These models have a very short and intense period of resonance which is qualitatively different from previous examples studied in this context, but we find that they lead to a similar spectrum of gravitational radiation.