Realistic hybrid inflation in five-dimensional orbifoldSO(10) grand unified theory

Abstract

We discuss the smooth hybrid inflation scenario in the context of a simple supersymmetricSO(10) grand unified theory (GUT) in a 5D orbifold. In this GUT model, theSO(10) gauge symmetry is broken down to the Pati–Salam (PS) gauge group,SU(4)c × SU(2)L × SU(2)R, by means of orbifold boundary conditions, and all matter and Higgs multiplets are placedonly on the brane (PS brane) where only the PS symmetry is manifest. Furtherbreaking of the Pati–Salam group to the standard model one is realized by meansof vacuum expectation values of the Higgs multiplets . The gauge coupling unification is successfully realized atMGUT = 4.6 × 1017 GeV after incorporating the threshold corrections of the Kaluza–Klein modes, with thecompactification scale (assumed to be the same as the PS symmetry breaking scale)Mc = vPS = 1.2 × 1016 GeV. We show that this orbifold GUT model can naturally lead us to smooth hybrid inflation, whichturns out to be consistent with the Wilkinson Microwave Anisotropy Probe five-year data, with theMGUT and vPS predicted within the model.