Hybrid Inflation Revisited in Light of WMAP5
  We study the effects of including one-loop radiative corrections in a
non-supersymmetric hybrid inflationary model. These corrections can arise from
Yukawa couplings between the inflaton and right-handed neutrinos, and induce a
maximum in the potential which admits hilltop-type solutions in addition to the
standard hybrid solutions. We obtain a red-tilted spectral index $n_s$,
consistent with WMAP5 data, for sub-Planckian values of the field. This is in
contrast to the tree level hybrid analysis, in which a red-tilted spectrum is
achieved only for trans-Planckian values of the field. Successful reheating is
obtained at the end of the inflationary phase via conversion of the inflaton
and waterfall fields into right-handed neutrinos, whose subsequent decay can
explain the observed baryon asymmetry via leptogenesis.
