GUT Scale And Leptogenesis From 5D Inflation

Abstract

We discuss a five dimensional inflationary scenario based on a supersymmetric SO(10) model compactified on $S^1/(Z_2\times Z_2^{\prime })$. 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 $\delta T/T\propto (M/M_{\mathrm{Planck}}{)}^2$, 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.

Comments: 1+16 pages, comments and references added, version to appear in PLB