• DOI:10.1103/PhysRevD.83.123502
• Corpus ID: 8096506

Generating Scale-Invariant Perturbations from Rapidly-Evolving Equation of State

@article{Khoury2011GeneratingSP,
  title={Generating Scale-Invariant Perturbations from Rapidly-Evolving Equation of State},
  author={Justin Khoury and Paul J. Steinhardt},
  journal={Physical Review D},
  year={2011},
  volume={83},
  pages={123502}
}

• J. Khoury, P. Steinhardt
• Published 18 January 2011
• Physics
• Physical Review D

Recently, we introduced an ekpyrotic model based on a single, canonical scalar field that generates nearly scale-invariant curvature fluctuations through a purely ''adiabatic mechanism'' in which the background evolution is a dynamical attractor. Despite the starkly different physical mechanism for generating fluctuations, the two-point function is identical to inflation. In this paper, we further explore this concept, focusing in particular on issues of non-Gaussianity and quantum corrections. We find that the degeneracy with inflation is broken at three-point level: for the simplest case of an exponential potential, the three-point amplitude is strongly scale dependent, resulting in a breakdown of perturbation theory on small scales. However, we show that the perturbative breakdown can be circumvented--and all issues raised in Linde et al. (arXiv:0912.0944) can be addressed--by altering the potential such that power is suppressed on small scales. The resulting range of nearly scale-invariant, Gaussian modes can be as much as 12 e-folds, enough to span the scales probed by microwave background and large-scale structure observations. On smaller scales, the spectrum is not scale invariant but is observationally acceptable.