Thermal and Non-Thermal Production of Gravitinos in the Early Universe

TL;DR

This paper examines both thermal and non-thermal mechanisms for gravitino production in the early universe, revealing that non-thermal processes can dominate and impose stricter constraints on the reheating temperature after inflation.

Contribution

It provides a detailed analysis of non-thermal gravitino production, including new tools for studying this process in dynamic backgrounds and initial numerical results for specific models.

Findings

Non-thermal gravitino production can surpass thermal production by several orders of magnitude.

Prolonged inflaton oscillations affect gravitino generation.

Numerical results demonstrate the significance of non-thermal processes in certain models.

Abstract

The excessive production of gravitinos in the early universe destroys the successful predictions of nucleosynthesis. The thermal generation of gravitinos after inflation leads to the bound on the reheating temperature, T_{RH}< 10^9 GeV. However, it has been recently realized that the non-thermal generation of gravitinos in the early universe can be extremely efficient and overcome the thermal production by several orders of magnitude, leading to much tighter constraints on the reheating temperature. In this paper, we first investigate some aspects of the thermal production of gravitinos, taking into account that in fact reheating is not instantaneous and inflation is likely to be followed by a prolonged stage of coherent oscillations of the inflaton field. We then proceed by further investigating the non-thermal generation of gravitinos, providing the necessary tools to study this process in a generic time-dependent background with any number of superfields. We also present the first numerical results regarding the non-thermal generation of gravitinos in particular supersymmetric models.