Scale invariance without inflation?

C. Armendáriz-Picón, Eugene A. Lim

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


We propose a new alternative mechanism to seed a scale invariant spectrum of primordial density perturbations that does not rely on inflation. In our scenario, a perfect fluid dominates the early stages of an expanding, non-inflating universe. Because the speed of sound of the fluid decays, perturbations are left frozen behind the sound horizon, with a spectral index that depends on the fluid equation of state. We explore here a toy model that realizes this idea. Although the model can explain an adiabatic, Gaussian, scale invariant spectrum of primordial perturbations, it turns out that in its simplest form it cannot account for the observed amplitude of the primordial density perturbations.

Original languageEnglish (US)
Pages (from-to)15-25
Number of pages11
JournalJournal of Cosmology and Astroparticle Physics
Issue number12
StatePublished - Dec 2003


  • Cosmological perturbation theory
  • Inflation

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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