Nonthermal Gravitino Production after Large Field Inflation

TL;DR

This paper investigates nonthermal gravitino production after inflation, highlighting how different inflation models with or without a stabilizer field affect gravitino abundance and cosmological safety.

Contribution

It provides a non-perturbative analysis of gravitino production in large field inflation models, especially those with a stabilizer superfield, which was previously unexplored.

Findings

Transverse gravitino production can be problematic in single-superfield models.

Production is suppressed in multi-superfield models with stabilizer fields.

The study clarifies the relation between background field and perturbative decay methods.

Abstract

We revisit the nonthermal gravitino production at the (p)reheating stage after inflation. Particular attention is paid to large field inflation models with a $\mathbb{Z}_2$ symmetry, for which the previous perturbative analysis is inapplicable; and inflation models with a stabilizer superfield, which have not been studied non-perturbatively. It is found that in single-superfield inflation models (without the stabilizer field), nonthermal production of the transverse gravitino can be cosmologically problematic while the abundance of the longitudinal gravitino is small enough. In multi-superfield inflation models (with the stabilizer field), production of the transverse and longitudinal gravitinos is significantly suppressed, and they are cosmologically harmless. We also clarify the relation between the background field method used in the preheating context and the standard perturbative decay method to estimate the gravitino abundance.