Covariant second-order perturbations in generalized two-field inflation

Eleftheria Tzavara, Shuntaro Mizuno, Bartjan Van Tent

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


We examine the covariant properties of generalized models of two-field inflation, with non-canonical kinetic terms and a possibly non-trivial field metric. We demonstrate that kinetic-term derivatives and covariant field derivatives do commute in a proper covariant framework, which was not realized before in the literature. We also define a set of generalized slow-roll parameters, using a unified notation. Within this framework, we study the most general class of models that allows for well-defined adiabatic and entropic sound speeds, which we identify as the models with parallel momentum and field velocity vectors. For these models we write the exact cubic action in terms of the adiabatic and isocurvature perturbations. We thus provide the tool to calculate the exact non-Gaussianity beyond slow-roll and at any scale for these generalized models. We illustrate our general results by considering their long-wavelength limit, as well as with the example of two-field DBI inflation.

Original languageEnglish
Article number027
JournalJournal of Cosmology and Astroparticle Physics
Issue number7
Publication statusPublished - 2014 Jul 1
Externally publishedYes


  • cosmological applications of theories with extra dimensions
  • cosmological perturbation theory
  • inflation
  • non-gaussianity

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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