Reducing the Spectral Index in Supernatural Inflation

Abstract

Supernatural inflation is an attractive model based just on a flat direction with soft SUSY breaking mass terms in the framework of supersymmetry. The beauty of the model is inferred from its name that the model needs no fine-tuning. However, the prediction of the spectral index is $n_s\text{gae}1$, in contrast to experimental data. In this paper, we show that the beauty of supernatural inflation with the spectral index reduced to $n_s=0.96$ without any fine-tuning, by considering the general feature that a flat direction is lifted by a non-renormalizable term with an A-term.

Comments: 6 pages, 1 figure, to be published in Physical Review D