Abstract :
We consider the cosmological and astrophysical constraints on the decay of massive E8 × E8′ superstring axions associated with the hidden sector. We find that decay lifetimes greater than 1 s are ruled out by limits from nucleosynthesis, by limits on the distortion of the cosmic microwave and gamma ray backgrounds and by closure arguments. We conclude that Λ > 1.2 × 1013 GeV, where Λ is the scale of gaugino condensation in the hidden sector. This implies that the scale of supersymmetry breaking is greater than 1010 GeV. Significantly, our result agrees with the value of 5 x 1013 GeV for Λ obtained independently by setting supersymmetric scalar masses equal to mw.
