Non-minimally gravity-coupled inflationary models

We consider the non-supersymmetric models of chaotic (driven by a quadratic potential) and hybrid inflation, taking into account the minimal possible radiative corrections to the inflationary potential. We show that two simple coupling functions f (sigma) (with a parameter c(R) involved) between the inflaton field sigma and the Ricci scalar curvature ensure, for sub-Planckian values of the inflaton field, observationally acceptable values for the spectral index, n(s), and sufficient reheating after inflation. In the case of chaotic inflation we consider two models with large c(R)'s resulting to n(s) similar or equal to 0.955 or 0.967 and tensor-to-scalar ratio r similar or equal to 0.2 or 0.003. respectively. In the case of hybrid inflation, the selected f (sigma) assists us to obtain hilltop-type inflation. For values of the relevant mass parameter, m, less than 10(6) TeV and the observationally central value of ns, we find c(R) similar or equal to (0.015-0.078) with the relevant coupling constants lambda = K and the symmetry breaking scale, M, confined in the ranges (2 . 10(-7)-0.001) and (1-16.8) . 10(17) GeV, respectively. (C) 2010 Elsevier B.V. All rights reserved.