Instabilities in Horndeski-Yang-Mills inflation

Jose Beltrán Jiménez, Lavinia Heisenberg, Ryotaro Kase, Ryo Namba, Shinji Tsujikawa

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16 Citations (Scopus)


A non-Abelian SU(2) gauge field with a nonminimal Horndeski coupling to gravity gives rise to a de Sitter solution followed by a graceful exit to a radiation-dominated epoch. In this Horndeski-Yang-Mills (HYM) theory we derive the second-order action for tensor perturbations on the homogeneous and isotropic quasi-de Sitter background. We find that the presence of the Horndeski nonminimal coupling to the gauge field inevitably introduces ghost instabilities in the tensor sector during inflation. Moreover, we also find Laplacian instabilities for the tensor perturbations deep inside the Hubble radius during inflation. Thus, we conclude that the HYM theory does not provide a consistent inflationary framework due to the presence of ghosts and Laplacian instabilities.

Original languageEnglish
Article number063533
JournalPhysical Review D
Issue number6
Publication statusPublished - 2017 Mar 31
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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