Realistic Hybrid Inflation in 5D Orbifold SO(10) GUT

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We discuss the smooth hybrid inflation scenario in the context of a simple supersymmetric SO(10) GUT in 5D orbifold. In this GUT model, the SO(10) gauge symmetry is broken down to the Pati-Salam (PS) gauge group, SU(4)c × SU(2)ₗ × SU(2)ᵣ, by orbifold boundary conditions and all matter and Higgs multiplets are placed only on the brane (PS brane) where only the PS symmetry is manifest. Further breaking of the Pati-Salam group to the Standard Model one is realized by VEVs of the Higgs multiplets (4, 1, 2) ⊕ (4, 1, 2). The gauge coupling unification is successfully realized at M GUT =4.6 × 10¹⁷ GeV after incorporating the threshold corrections of the Kaluza-Klein modes, with the compactification scale (assumed to be the same as the PS symmetry breaking scale) Mc = v PS= 1.2 × 10¹⁶ GeV. We show that this orbifold GUT model can naturally leads us to the smooth hybrid inflation, which tunes out to be consistent with the WMAP 5-year data with the predicted M GUT and vPS in the model.