Reheating and preheating in the simplest extension of Starobinsky inflation

TL;DR

This paper investigates how an $R^2$ correction in a simple extension of Starobinsky inflation influences reheating and preheating, affecting expansion rates, decay processes, and particle production, which are crucial for matching theory with observations.

Contribution

It demonstrates that gravitational corrections due to the $R^2$ term significantly impact reheating and preheating dynamics in extended Starobinsky models.

Findings

Reheating temperature and duration are slightly affected by $R^2$ corrections.

Gravitational effects can alter the decay of the second scalar field during preheating.

Particle production is strongly influenced for certain parameter values.

Abstract

The epochs of reheating and preheating are studied in a simple extension of the Starobinsky inflationary model, which consists of an $R^2$--correction to the Einstein--Hilbert action and an additional scalar field. We find that if the $R^2$--correction at the end of inflation is dynamically important, it affects the expansion rate and as a consequence the reheating and preheating processes. While we find that the reheating temperature and duration of reheating are only slightly affected, the effect has to be taken into account when comparing the theory to data. In the case of preheating, the gravitational corrections can significantly affect the decay of the second field. Particle production is strongly affected for certain values of the parameters in the theory.