GUT scale and leptogenesis from 5D inflation

We discuss a five-dimensional inflationary scenario based on a supersymmetric SO(10) model compactified on S1/(Z2×Z2′). Inflation is implemented through scalar potentials on four-dimensional branes, and a brane-localized Einstein–Hilbert term is essential to make both brane vacuum energies positive during inflation. The orbifold boundary conditions break the SO(10) gauge symmetry to SU(4)c×SU(2)L×SU(2)R (≡H). The inflationary scenario yields δT/T∝(M/MPlanck)2, which fixes M, the symmetry breaking scale of H to be close to the SUSY GUT scale of 1016 GeV. The scalar spectral index n is 0.98–0.99, while the gravitational wave contribution to the quadrupole anisotropy is negligible (≲1%). The inflaton decay into the lightest right-handed neutrinos yields the observed baryon asymmetry via leptogenesis.