Moduli Backreaction on Inflationary Attractors

TL;DR

This paper explores how moduli fields interact with inflation in string-inspired models, showing that for $ extalpha$-attractors, inflation remains stable despite potential backreaction, and discusses implications for cosmological predictions.

Contribution

It demonstrates that $ extalpha$-attractor models are robust against moduli backreaction, ensuring stable inflation and consistent observational predictions without fine-tuning.

Findings

Moduli backreaction can destabilize inflation but generally does not for $ extalpha$-attractors.

The volume modulus can be stable or act as a waterfall field depending on the superpotential.

Inflationary predictions remain compatible with Planck data across scenarios.

Abstract

We investigate the interplay between moduli dynamics and inflation, focusing on the KKLT-scenario and cosmological $\alpha$-attractors. General couplings between these sectors can induce a significant backreaction and potentially destroy the inflationary regime; however, we demonstrate that this generically does not happen for $\alpha$-attractors. Depending on the details of the superpotential, the volume modulus can either be stable during the entire inflationary trajectory, or become tachyonic at some point and act as a waterfall field, resulting in a sudden end of inflation. In the latter case there is a universal supersymmetric minimum where the scalars end up, preventing the decompactification scenario. The gravitino mass is independent from the inflationary scale with no fine-tuning of the parameters. The observational predictions conform to the universal value of attractors, fully compatible with the Planck data, with possibly a capped number of e-folds due to the interplay with moduli.