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 ck 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, ns, and sufficient reheating after inflation. In the case of chaotic
inflation we consider two models with large ck's resulting to ns=0.955 or 0.967
and tensor-to-scalar ratio r=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 ck=(0.015-0.078) with the relevant
coupling constants lambda=kappa and the symmetry breaking scale, M, confined in
the ranges (2x 10^{-7}-0.001) and (1-16.8)x10^{17} GeV, respectively.
