Non-Gaussian inflationary shapes in G3 theories beyond Horndeski

Matteo Fasiello, Sébastien Renaux-Petel

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We consider the possible signatures of a recently introduced class of healthy theories beyond Horndeski models on higher-order correlators of the inflationary curvature fluctuation. Despite the apparent large number and complexity of the cubic interactions, we show that the leading-order bispectrum generated by the Generalized Horndeski (also called G3) interactions can be reduced to a linear combination of two well known k-inflationary shapes. We conjecture that said behavior is not an accident of the cubic order but a consequence dictated by the requirements on the absence of Ostrogradski instability, the general covariance and the linear dispersion relation in these theories.
Original languageEnglish
Article number037
JournalJournal of Cosmology and Astroparticle Physics
Issue number10
Publication statusPublished - 15 Oct 2014


  • astro-ph.CO
  • gr-qc
  • hep-th


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