Gravity Waves and Proton Decay in Flipped SU(5) Hybrid Inflation Model

Abstract

We revisit supersymmetric hybrid inflation in the context of flipped $SU(5)$ model. With minimal superpotential and minimal Kähler potential, and soft SUSY masses of order $(1-100)$ TeV, compatibility with the Planck data yields a symmetry breaking scale $M$ of flipped $SU(5)$ close to $(2-4)\times 10^{15}$ GeV. This disagrees with the lower limit $M\gtrsim 7\times 10^{15}$ GeV set from proton decay searches by the Super-Kamiokande collaboration. We show how $M$ close to the unification scale $2\times 10^{16}$ GeV can be reconciled with SUSY hybrid inflation by employing a non-minimal Kähler 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 $\sim 10^{-4}-10^{-3}$.

Comments: 15 pages, 12 figures