GUT Scale And Leptogenesis From 5D Inflation

We discuss a five dimensional inflationary scenario based on a supersymmetric SO(10) model compactified on $S^1\mathrm{/}(Z_2\times Z_2^{\mathrm{\prime }})$. 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 $SU(4{)}_c\times SU(2{)}_L\times SU(2{)}_R$ ($\equiv H$). The inflationary scenario yields $\delta T\mathrm{/}T\propto (M\mathrm{/}{M}_{\mathrm{P}\mathrm{l}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{k}}{)}^2$, which fixes $M$, the symmetry breaking scale of $H$ to be close to the SUSY GUT scale of ${10}^{16}$ GeV. The scalar spectral index $n$ is $0.98-0.99$, while the gravitational wave contribution to the quadrupole anisotropy is negligible (\lapproxeq 1 {%}). The inflaton decay into the lightest right handed neutrinos yields the observed baryon asymmetry via leptogenesis.