Waterfall field in hybrid inflation and curvature perturbation

Jinn Ouk Gong, Misao Sasaki

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


We study carefully the contribution of the waterfall field to the curvature perturbation at the end of hybrid inflation. In particular we clarify the parameter dependence analytically under reasonable assumptions on the model parameters. After calculating the mode function of the waterfall field, we use the δN formalism and confirm the previously obtained result that the power spectrum is very blue with the index 4 and is absolutely negligible on large scales. However, we also find that the resulting curvature perturbation is highly non-Gaussian and hence we calculate the bispectrum. We find that the bispectrum is at leading order independent of momentum and exhibits its peak at the equilateral limit, though it is unobservably small on large scales. We also present the one-point probability distribution function of the curvature perturbation.

Original languageEnglish
Article number028
JournalJournal of Cosmology and Astroparticle Physics
Issue number3
StatePublished - Mar 2011


  • cosmological perturbation theory
  • inflation
  • physics of the early universe


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