Constraints on supersymmetric grand unified theories from cosmology

Abstract

Within the context of SUSY GUTs, cosmic strings are generically formed at the end ofhybrid inflation. However, the WMAP CMB measurements strongly constrain the possiblecosmic strings contribution to the angular power spectrum of anisotropies. We investigatethe parameter space of SUSY hybrid (F- and D-term) inflation, to get the conditionsunder which theoretical predictions are in agreement with data. The predictions ofF-term inflation are in agreement with data only if the superpotential couplingκ is small. Inparticular, for SUSY SO(10), the upper bound is . This fine tuning problem can be lifted if we employ the curvaton mechanism, in whichcase ; higher values are not allowed by the gravitino constraint. The constraint onκ is equivalent to a constraint on the SSB mass scaleM, namely GeV.The study of D-term inflation shows that the inflaton field is of the order of the Planck scale;one should therefore consider SUGRA. We find that the cosmic strings contribution to theCMB anisotropies is not constant, but it is strongly dependent on the gauge couplingg and on thesuperpotential coupling λ. We obtain and . SUGRA corrections also induce a lower limit forλ. Equivalently, theFayet–Iliopoulos term ξ must satisfy GeV. This constraint holds for all allowed values ofg.