Adiabatic CMB perturbations in pre - big bang string cosmology

  title={Adiabatic CMB perturbations in pre - big bang string cosmology},
  author={Kari Enqvist and Martin S. Sloth},
  journal={Nuclear Physics},
Abstract We consider the pre-Big-Bang scenario with a massive axion field which starts to dominate energy density when oscillating in an instanton-induced potential and subsequently reheats the universe as it decays into photons, thus creating adiabatic CMB perturbations. We find that the fluctuations in the axion field can give rise to a nearly flat spectrum of adiabatic perturbations with a spectral tilt Δn in the range −0.1≲ Δn ≲1. 

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