Flipped SU(5) Predicts $\delta T/T$

Abstract

We discuss hybrid inflation in supersymmetric flipped SU(5) model such that the cosmic microwave anisotropy $\delta T/T$ is essentially proportional to $(M/M_P{)}^2$, where $M$ denotes the symmetry breaking scale and $M_P$ ($=2.4\times 10^{18}$ GeV) is the reduced Planck mass. The magnitude of $M$ determined from $\delta T/T$ measurements can be consistent with the value inferred from the evolution of SU(3) and SU(2) gauge couplings. In other words, one could state that flipped SU(5) predicts (more precisely `postdicts') $\delta T/T$. The scalar spectral index $n_s=0.993\pm 0.007$, the scalar to tensor ratio satisfies $r\text{lapproxeq}10^{-6}$, while $d{n}_s/d\ln k\text{lapproxeq}4\times 10^{-4}$.

Comments: 1+15 pages, 6 figures, version to appear in Phys. Lett. B