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Revisiting non-Gaussianity in multifield inflation with curved field space

  • Sebastian Garcia-Saenz
  • Lucas Pinol
  • Sébastien Renaux-PetelEmail author
Open Access
Regular Article - Theoretical Physics

Abstract

Recent studies of inflation with multiple scalar fields have highlighted the importance of non-canonical kinetic terms in novel types of inflationary solutions. This motivates a thorough analysis of non-Gaussianities in this context, which we revisit here by studying the primordial bispectrum in a general two-field model. Our main result is the complete cubic action for inflationary fluctuations written in comoving gauge, i.e. in terms of the curvature perturbation and the entropic mode. Although full expressions for the cubic action have already been derived in terms of fields fluctuations in the flat gauge, their applicability is mostly restricted to numerical evaluations. Our form of the action is instead amenable to several analytical approximations, as our calculation in terms of the directly observable quantity makes manifest the scaling of every operator in terms of the slow-roll parameters, what is essentially a generalization of Maldacena’s single-field result to non-canonical two-field models. As an important application we derive the single-field effective field theory that is valid when the entropic mode is heavy and may be integrated out, underlining the observable effects that derive from a curved field space.

Keywords

Cosmology of Theories beyond the SM Effective Field Theories Sigma Models 

Notes

Open Access

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited

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Copyright information

© The Author(s) 2020

Authors and Affiliations

  • Sebastian Garcia-Saenz
    • 1
  • Lucas Pinol
    • 1
  • Sébastien Renaux-Petel
    • 1
    Email author
  1. 1.Institut d’Astrophysique de Paris, GReCO, UMR 7095 du CNRS et de Sorbonne UniversitéParisFrance

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