SUGRA chaotic inflation and moduli stabilisation

TL;DR

This work analyzes the viability of embedding chaotic inflation in ${\mathcal N}=1$ supergravity with a stabilised modulus sector, comparing KKLT and Kallosh–Linde (KL) constructions. It shows that generic KKLT moduli destabilise large-field inflation because achieving $H^2\ll m_{\rm mod}^2$ conflicts with keeping soft inflaton corrections small; KL can work, but only under a fine-tuned modulus potential and for a specific Kähler form. Critically, treating the modulus as a dynamical field during inflation reveals potential tachyonic instabilities unless the inflaton-sector superpotential is arranged so that $(W_{\rm inf})_i=0$ for all inflaton fields; among tested setups, only model 1 with a Kähler potential that keeps the spectator field outside the logarithm yields a viable inflation with small moduli backreaction and nearly quadratic predictions ($n_s\approx0.967$) while allowing possible small deviations or isocurvature signals depending on parameters. The results provide concrete criteria for constructing consistent SUGRA chaotic inflation models with stabilized moduli and highlight potential observational signatures that could reveal modulus dynamics in the early universe.

Abstract

Chaotic inflation predicts a large gravitational wave signal which can be tested by the upcoming Planck satellite. We discuss a SUGRA implementation of chaotic inflation in the presence of moduli fields, and find that inflation does not work with a generic KKLT moduli stabilisation potential. A viable model can be constructed with a fine-tuned moduli sector, but only for a very specific choice of Kahler potential. Our analysis also shows that inflation models satisfying \partial_{i} W_{\rm inf}=0 for all inflation sector fields φ_i can be combined successfully with a fine-tuned moduli sector.

Figures (2)

• Figure 1: $V(\varphi_1,\varphi_2)$ (in rescaled units) with $\sigma$ at instantaneous minimum for model 1 (left) and model 2 (right top).
• Figure 2: Results for model 1 with parameters $A=1,\,B=1.4,\,a=0.2,\,b=0.3,\, \delta = 10^{-8}$. Left plot shows field evolution of $\varphi_1$ (rescaled), $\varphi_2$ and $\delta T = T - T_0$ during inflation. Right plot shows the inflaton mass eigenstates as function of time $N$.