Smooth μ-Hybrid and Non-Minimal Higgs Inflation in $SU(4)C× SU(2)L× SU(2)R$ With Observable Gravitational Waves

We propose to study a smooth variant of the μ-hybrid inflation model and a non-minimal Higgs model of inflation with quartic non-minimal coupling between the Higgs field and gravity within the context of a realistic GUT gauge group based on supersymmetric SU(4)C× SU(2)L× SU(2)R. These models are incorporated with a realistic scenario of reheating and non-thermal leptogenesis, compatible with the constraints from the baryon asymmetry of the universe. Notably, both models successfully address the MSSM μ-problem and avoid the issue of primordial magnetic monopoles. Our analysis reveals that both models predict a scalar spectral index nₛ that closely aligns with the central observationally favored value of Planck2018 + BICEP2/Keck Array (BK15) data and yield a large tensor-to-scalar ratio (r > 10⁻³), potentially detectable in forthcoming CMB experiments.