Challenges for Large-Field Inflation and Moduli Stabilization

TL;DR

This paper explores the challenges of integrating large-field inflation with moduli stabilization in supergravity, revealing universal inflationary predictions and the necessity of high supersymmetry breaking scales.

Contribution

It demonstrates that supersymmetry breaking effects prevent decoupling of moduli during inflation, leading to a universal flattened inflaton potential across different stabilization models.

Findings

Inflation driven by a soft mass term related to supersymmetry breaking.

Universal flattened inflaton potential across models.

Lower bound on tensor-to-scalar ratio, r ≥ 0.05.

Abstract

We analyze the interplay between K\"ahler moduli stabilization and chaotic inflation in supergravity. While heavy moduli decouple from inflation in the supersymmetric limit, supersymmetry breaking generically introduces non-decoupling effects. These lead to inflation driven by a soft mass term, $m_\varphi^2 \sim m m_{3/2}$, where $m$ is a supersymmetric mass parameter. This scenario needs no stabilizer field, but the stability of moduli during inflation imposes a large supersymmetry breaking scale, $m_{3/2} \gg H$, and a careful choice of initial conditions. This is illustrated in three prominent examples of moduli stabilization: KKLT stabilization, K\"ahler Uplifting, and the Large Volume Scenario. Remarkably, all models have a universal effective inflaton potential which is flattened compared to quadratic inflation. Hence, they share universal predictions for the CMB observables, in particular a lower bound on the tensor-to-scalar ratio, $r \gtrsim 0.05$.