On scale-free extensions of massive (bi-)gravity

Giulia Cusin, Nima Khosravi, Johannes Noller

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We discuss a scale-free model of bigravity, in which the mass parameter of the standard bigravity potential is promoted to a dynamical scalar field. This modification retains the ghost-free bigravity structure, in particular it remains free of the Boulware-Deser ghost. We investigate the theory’s interaction structure, focusing on its consistent scaling limits and strong coupling scales. Furthermore we explore the model’s quadratic action, both around generic background configurations and paying special attention to cosmological backgrounds and to the associated background evolution. Finally we consider the possibility of realising a phase of late-time acceleration as well as a quasi-de Sitter inflationary stage at early times, when the promoted “mass scalar” becomes the inflaton.
Original languageEnglish
Article number98
Pages (from-to)1-35
Number of pages35
JournalJournal of High Energy Physics
Issue number2
Publication statusPublished - 20 Feb 2017


  • classical theories of gravity
  • space-time symmetries


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