Gravity waves and proton decay in a flipped SU(5) hybrid inflation model

We revisit supersymmetric hybrid inflation in the context of the flipped SU(5) model. With minimal superpotential and minimal Kahler potential, and soft supersymmetry (SUSY) masses of order (1-100) TeV, compatibility with the Planck data yields a symmetry breaking scale M of flipped SU(5) close to (2- 4) x 10(15) GeV. This disagrees with the lower limit M greater than or similar to 7 x 10(15) GeV set from proton decay searches by the Super-Kamiokande collaboration. We show how M close to the unification scale 2 x 10(16) GeV can be reconciled with SUSY hybrid inflation by employing a nonminimal Kahler potential. Proton decays into e(+)pi(0) with an estimated lifetime of order 10(36) years. The tensor to scalar ratio r in this case can approach observable values similar to 10(-4)-10(-3).