Dark energy or modified gravity? An effective field theory approach

Jolyon Bloomfield, Éanna É Flanagan, Minjoon Park, Scott Watson

Research output: Contribution to journalArticlepeer-review

221 Scopus citations


We take an Effective Field Theory (EFT) approach to unifying existing proposals for the origin of cosmic acceleration and its connection to cosmological observations. Building on earlier work where EFT methods were used with observations to constrain the background evolution, we extend this program to the level of the EFT of the cosmological perturbations - following the example from the EFT of Inflation. Within this framework, we construct the general theory around an assumed background which will typically be chosen to mimic ΛCDM, and identify the parameters of interest for constraining dark energy and modified gravity models with observations. We discuss the similarities to the EFT of Inflation, but we also identify a number of subtleties including the relationship between the scalar perturbations and the Goldstone boson of the spontaneously broken time translations. We present formulae that relate the parameters of the fundamental Lagrangian to the speed of sound, anisotropic shear stress, effective Newtonian constant, and Caldwell's parameter, emphasizing the connection to observations. It is anticipated that this framework will be of use in constraining individual models, as well as for placing model-independent constraints on dark energy and modified gravity model building.

Original languageEnglish (US)
Article number010
JournalJournal of Cosmology and Astroparticle Physics
Issue number8
StatePublished - Aug 2013


  • dark energy theory
  • modified gravity

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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