TY - JOUR
T1 - Spatially covariant theories of gravity
T2 - Disformal transformation, cosmological perturbations and the Einstein frame
AU - Fujita, Tomohiro
AU - Gao, Xian
AU - Yokoyama, Jun'ichi
N1 - Funding Information:
T.F. acknowledges the supported by JSPS Postdoctoral fellowship for Research Abroad (Grant No. 27-154). X.G. was supported by JSPS Grant-in-Aid for Scientific Research No. 25287054 and 26610062. The work of J.Y. was supported by JSPS Grant-in-Aid for Scientific Research No. 15H02082, and the JSPS Grant-in-Aid for Scientific Research on Innovative Areas No. 15H05888.
Publisher Copyright:
© 2016 IOP Publishing Ltd and Sissa Medialab srl.
PY - 2016/2/4
Y1 - 2016/2/4
N2 - 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.
AB - 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.
KW - cosmological perturbation theory
KW - modified gravity
KW - primordial gravitational waves (theory)
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U2 - 10.1088/1475-7516/2016/02/014
DO - 10.1088/1475-7516/2016/02/014
M3 - Article
AN - SCOPUS:84960116954
SN - 1475-7516
VL - 2016
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
IS - 2
M1 - 014
ER -