Gravitational Production of Spin-3/2 Particles During Reheating

TL;DR

This paper calculates the gravitational production of spin-3/2 particles, called raritrons, during reheating after inflation, showing it exceeds thermal production and setting constraints on their mass and stability.

Contribution

It provides the first detailed computation of gravitational raritron production during reheating, including the effects of a inflaton condensate and comparison with gravitino production.

Findings

Raritron production surpasses thermal bath contributions.

A minimum mass for stable raritrons is established based on relic abundance.

Comparison with gravitino production mechanisms highlights differences in early universe particle generation.

Abstract

We compute the density of a spin-$\frac32$ particle, the raritron, produced at the end of inflation due to gravitational interactions. We consider a background inflaton condensate as the source of this production, mediated by the exchange of a graviton. This production greatly exceeds the gravitational production from the emergent thermal bath during reheating. The relic abundance limit sets an absolute minimum mass for a stable raritron, though there are also model dependent constraints imposed by unitarity. We also examine the case of gravitational production of a gravitino, taking into account the goldstino evolution during reheating. We compare these results with conventional gravitino production mechanisms.