Generating ekpyrotic curvature perturbations before the big bang

Jean Luc Lehners, Paul McFadden, Neil Turok, Paul J. Steinhardt

Research output: Contribution to journalArticlepeer-review

174 Scopus citations


We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, which can be entirely described using 4D effective field theory. The mechanism, based on first producing entropic perturbations and then converting them to curvature perturbations, can be naturally incorporated in cyclic and ekpyrotic models in which the big bang is modeled as a brane collision, as well as other types of cosmological models with a pre-big bang phase. We show that the correct perturbation amplitude can be obtained and that the spectral tilt ns tends to range from slightly blue to red, with 0.97<ns<1.02 for the simplest models, a range compatible with current observations but shifted by a few percent towards the blue compared to the prediction of the simplest, large-field inflationary models.

Original languageEnglish (US)
Article number103501
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number10
StatePublished - Nov 1 2007

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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