Superconformal D-Term Inflation

TL;DR

This paper investigates superconformal supergravity models of hybrid inflation, finding D-term inflation viable for matching observed primordial spectra, while F-term inflation faces challenges due to large tachyonic masses.

Contribution

It demonstrates that D-term hybrid inflation within superconformal supergravity can successfully produce the observed primordial power spectrum and spectral index.

Findings

D-term hybrid inflation can match the amplitude of primordial fluctuations.

The model yields spectral index values down to approximately 0.96.

There is a tension between spectral index and cosmic string bounds, but current data can accommodate both within uncertainties.

Abstract

We study models of hybrid inflation in the framework of supergravity with superconformal matter. F-term hybrid inflation is not viable since the inflaton acquires a large tachyonic mass. On the contrary, D-term hybrid inflation can successfully account for the amplitude of the primordial power spectrum. It is a two-field inflation model which, depending on parameters, yields values of the scalar spectral index down to n_s ~ 0.96. Generically, there is a tension between a small spectral index and the cosmic string bound albeit, within 2-sigma uncertainty, the current observational bounds can be simultaneously fulfilled.