Reducing the spectral index in F-term hybrid inflation

Understand

We consider a class of well motivated supersymmetric models of F-term hybrid inflation (FHI) which can be linked to the supersymmetric grand unification.

• The predicted scalar spectral index n_s cannot be smaller than 0.97 and can exceed unity including corrections from minimal supergravity, if the number of e-foldings corresponding to the pivot scale k_*=0.002/Mpc is around 50.
• These results are marginally consistent with the fitting of the three-year Wilkinson microwave anisotropy probe data by the standard power-law cosmological model with cold dark matter and a cosmological constant.
• However, n_s can be reduced by applying two mechanisms: (i) The utilization of a quasi-canonical Kahler potential with a convenient choice of a sign and (ii) the restriction of the number of e-foldings that k_* suffered during FHI.