GUT scale and leptogenesis from 5D inflation

We discuss a five-dimensional inflationary scenario based on a supersymmetric <f>SO(10)</f> model compactified on <f>S1/(Z2×Z2′)</f>. 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 <f>SO(10)</f> gauge symmetry to <f>SU(4)c×SU(2)L×SU(2)R</f> (<f>≡H</f>). The inflationary scenario yields <f>δT/T∝(M/MPlanck)2</f>, which fixes <f>M</f>, the symmetry breaking scale of <f>H</f> to be close to the SUSY GUT scale of <f>1016</f> GeV. The scalar spectral index <f>n</f> is <f>0.98</f>–<f>0.99</f>, while the gravitational wave contribution to the quadrupole anisotropy is negligible (<f>&lsim;1%</f>). The inflaton decay into the lightest right-handed neutrinos yields the observed baryon asymmetry via leptogenesis. [Copyright &y& Elsevier]