Simplified Smooth Hybrid Inflation in Supersymmetric SU(5)

Abstract

A scheme of simplified smooth hybrid inflation is realized in the framework of supersymmetric $SU(5)$. The smooth model of hybrid inflation provides a natural solution to the monopole problem that appears in the breaking of $SU(5)$ gauge symmetry. The supergravity corrections with nonminimal Kähler potential are shown to play important role in realizing inflation with a red-tilted scalar spectral index $n_s<1$, within Planck's latest bounds. As compared to shifted model of hybrid inflation, relatively large values of the tensor-to-scalar ratio $r\lesssim 0.01$ are achieved here, with nonminimal couplings $-0.05\lesssim {\kappa }_S\lesssim 0.01$ and $-1\lesssim {\kappa }_{SS}\lesssim 1$ and the gauge symmetry-breaking scale $M\simeq (2.0-16.7)\times 10^{16}$ GeV.

Comments: 11 pages, 7 figures, minor revisions to match published version