Inflation, the scale of supersymmetry breaking, and moduli stabilization

TL;DR

This paper reviews how heavy scalar fields in supergravity models influence inflation dynamics, highlighting backreaction effects that can alter inflationary potentials, especially when these fields break supersymmetry, with implications for model building.

Contribution

It provides a detailed analysis of backreaction effects of heavy scalars on inflation, emphasizing the impact of supersymmetry breaking in moduli stabilization scenarios.

Findings

Heavy scalars cause backreactions that modify inflation potentials.

Backreactions can flatten or spoil the inflationary plateau.

Supersymmetry breaking in heavy fields is a key factor in these effects.

Abstract

We review the effects of heavy scalar fields during inflation in the framework of $\mathcal N = 1$ supergravity. Such heavy scalars can be geometric moduli from string compactifications or stabilizer fields from a different sector of the theory. Even when these fields are heavier than the Hubble scale during inflation, they generically cause backreactions which alter the dynamics of the system. Severe problems may arise when the heavy fields break supersymmetry, which is quite generic for K\"ahler moduli. We illustrate these effects in two examples, chaotic inflation and Starobinsky-like inflation. In chaotic inflation the backreaction of heavy K\"ahler moduli causes a flattening of the quadratic potential. In many setups of Starobinsky-like inflation, however, backreactions spoil the flatness of the plateau.