Scale invariance via a phase of slow expansion

@article{Joyce2011ScaleIV,
  title={Scale invariance via a phase of slow expansion},
  author={Austin Joyce and Justin Khoury},
  journal={Physical Review D},
  year={2011},
  volume={84},
  pages={023508}
}
We consider a cosmological scenario in which a scale-invariant spectrum of curvature perturbations is generated by a rapidly-evolving equation of state on a slowly expanding background. This scenario generalizes the "adiabatic ekpyrotic" mechanism proposed recently in arXiv:0910.2230. Whereas the original proposal assumed a slowly contracting background, the present work shows that the mechanism works equally well on an expanding background. This greatly expands the realm of broader… 
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