Grand unified inflation confronts WMAP

In a class of realistic four and five dimensional supersymmetric grandunified models, the scalar spectral index is found to be $n_s=0.98 (\pm 0.01)$,in excellent agreement with the values determined by several previousexperiments and most recently by the Wilkinson Microwave Anisotropy Probe(WMAP). The models predict $dn_s/d{\rm ln}k\sim 10^{-3}$ and a negligibletensor-to-scalar ratio $r\sim 10^{-8}$. A new five dimensional supersymmetricSO(10) model along these is presented in which inflation is associated with thebreaking of SO(10) to SU(5) at scale $M$, with $\delta T/T\propto (M/M_{\rmPlanck})^2$, so that $M\simeq 10^{16}$ GeV. The inflaton decay leads to theobserved baryon asymmetry via leptogenesis. We also discuss how the monopoleproblem is solved without the use of non-renormalizable terms.Comment: A new resolution of the monopole problem proposed. 1+9 page