The minimal F-term hybrid inflation model is defined by a unique renormalizable superpotential, fixed by a U(1) R-symmetry, and employs a minimal canonical Kaehler potential. The inflationary potential takes into account both radiative and supergravity corrections, as well as an important soft supersymmetry breaking term. With n_s in the vicinity of 0.96-0.97, as strongly indicated by the recent PLANCK and WMAP-9yr measurements, the model predicts that the tensor to scalar ratio r is extremely tiny, of order 10^-14 - 10^-11, and therefore well outside the reach of PLANCK and other contemporary experiments. It also predicts that |dn_s/dlnk|~ 4 x 10^-4. If inflation is associated with the spontaneous breaking of a local U(1) symmetry such as B-L, the symmetry breaking scale is predicted to be 1-2 x 10^15 GeV. Consequently, this scenario is naturally compatible with seesaw physics and non-thermal leptogenesis can be readily implemented. We also comment on the constraints that arise due to cosmic strings from the U(1) symmetry breaking.
Dr Konstantinus Pallis (University of Cyprus)