Fast computation of bispectrum features with generalized slow roll

Peter Adshead, Wayne Hu, Cora Dvorkin, Hiranya V. Peiris

Research output: Contribution to journalArticlepeer-review


We develop a fast technique based on the generalized slow-roll (GSR) approach for computing the curvature bispectrum of inflationary models with features. We show that all triangle configurations can be expressed in terms of three simple integrals over the inflationary background with typical accuracy of better than ∼20%. With a first-order GSR approach the typical accuracy can be improved to better than the ∼5% level. We illustrate this technique with the step potential model that has been invoked to explain the WMAP temperature power spectrum glitches at ℓ∼20-40 and show that the maximum likelihood model falls short of observability by more than a factor of 100 in amplitude. We also explicitly demonstrate that the bispectrum consistency relation with the local slope of the power spectrum is satisfied for these models. In the GSR approach, the bispectrum arises from integrals of nearly the same function of the background slow-roll parameters as the power spectrum but with a stronger weight to the epoch before horizon crossing. Hence this technique enables reverse engineering of models with large bispectrum but small power spectrum features.

Original languageEnglish (US)
Article number043519
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number4
StatePublished - Aug 12 2011
Externally publishedYes

ASJC Scopus subject areas

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


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