Gravitino Production Suppressed by Dynamics of Sgoldstino

TL;DR

This paper demonstrates that the early dynamics of the sgoldstino field can significantly suppress gravitino production in the early Universe, potentially resolving the gravitino problem and allowing higher reheat temperatures compatible with leptogenesis.

Contribution

It introduces a mechanism where the early evolution of the sgoldstino field reduces gravitino abundance, relaxing the traditional reheat temperature constraints in supersymmetric cosmology.

Findings

Gravitino production is suppressed by large initial sgoldstino field values.

Reheat temperature bounds can be relaxed, enabling thermal leptogenesis.

The cosmological evolution of the sgoldstino is crucial for early Universe dynamics.

Abstract

In supersymmetric theories, the gravitino is abundantly produced in the early Universe from thermal scattering, resulting in a strong upper bound on the reheat temperature after inflation. We point out that the gravitino problem may be absent or very mild due to the early dynamics of a supersymmetry breaking field, i.e. a sgoldstino. In models of low scale mediation, the field value of the sgoldstino determines the mediation scale and is in general different in the early Universe from the present one. A large initial field value since the era of the inflationary reheating suppresses the gravitino production significantly. We investigate in detail the cosmological evolution of the sgoldstino and show that the reheat temperature may be much higher than the conventional upper bound, restoring the compatibility with thermal leptogenesis.