Reheating After Quintessential Inflation and Gravitational Waves

TL;DR

This paper studies how different reheating processes after quintessential inflation affect the spectrum of primordial gravitational waves, especially around 100 MHz, providing insights into the early universe's thermal history.

Contribution

It compares two extreme reheating scenarios and demonstrates their distinct impacts on gravitational wave spectra, highlighting the potential of high-frequency gravitational wave detection to probe reheating.

Findings

Gravitational wave spectrum at ~100 MHz is highly sensitive to reheating details.

Detection of high-frequency gravitational waves can reveal reheating mechanisms.

Reheating effects are applicable across various inflation models.

Abstract

We investigate the dependence of the gravitational wave spectrum from quintessential inflation on the reheating process. We consider two extreme reheating processes. One is the gravitational reheating by particle creation in the expanding universe in which the beginning of the radiation dominated epoch is delayed due to the presence of the epoch of domination of the kinetic energy of the inflaton (kination). The other is the instant preheating considered by Felder et al. in which the Universe becomes radiation dominated soon after the end of inflation. We find that the spectrum of the gravitational waves at $\sim 100$ MHz is quite sensitive to the reheating process. This result is not limited to quintessential inflation but applicable to various inflation models. Conversely, the detection or non-detection of primordial gravitational waves at $\sim$100 MHz would provide useful information regarding the reheating process in inflation.