Spatially covariant theories of gravity: Disformal transformation, cosmological perturbations and the Einstein frame

Tomohiro Fujita, Xian Gao, Jun'ichi Yokoyama

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

We investigate the cosmological background evolution and perturbations in a general class of spatially covariant theories of gravity, which propagates two tensor modes and one scalar mode. We show that the structure of the theory is preserved under the disformal transformation. We also evaluate the primordial spectra for both the gravitational waves and the curvature perturbation, which are invariant under the disformal transformation. Due to the existence of higher spatial derivatives, the quadratic Lagrangian for the tensor modes itself cannot be transformed to the form in the Einstein frame. Nevertheless, there exists a one-parameter family of frames in which the spectrum of the gravitational waves takes the standard form in the Einstein frame.

Original languageEnglish
Article number014
JournalJournal of Cosmology and Astroparticle Physics
Volume2016
Issue number2
DOIs
Publication statusPublished - 2016 Feb 4
Externally publishedYes

Keywords

  • cosmological perturbation theory
  • modified gravity
  • primordial gravitational waves (theory)

ASJC Scopus subject areas

  • Astronomy and Astrophysics

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