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

TL;DR

This paper examines supersymmetric hybrid inflation within the flipped SU(5) model, addressing the tension between the symmetry breaking scale and proton decay limits, and explores how non-minimal Kähler potentials can reconcile these issues while predicting observable gravitational wave signals.

Contribution

It demonstrates how non-minimal Kähler potentials can reconcile the inflationary scale with proton decay constraints in flipped SU(5) models.

Findings

Symmetry breaking scale M close to 2-4 x 10^{15} GeV compatible with Planck data.

Proton decay lifetime estimated around 10^{36} years.

Tensor-to-scalar ratio r can reach observable levels ~10^{-4} - 10^{-3}.

Abstract

We revisit supersymmetric hybrid inflation in the context of flipped $SU(5)$ model. With minimal superpotential and minimal K\"ahler 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 K\"ahler 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 $\sim 10^{-4} - 10^{-3}$.