Modified gravity models of dark energy

S. Tsujikawa*

*この研究の対応する著者

研究成果査読

256 被引用数 (Scopus)

抄録

We review the recent progress for modified gravity models of dark energy - including f(R) gravity, scalar-tensor theories, and braneworld models. In f(R) gravity, where the Lagrangian density f is a function of the Ricci scalar R, the coupling strength between dark energy and non-relativistic matter is of order 1 ( ) in the Einstein frame. Even in this situation it is possible for f(R) models to be consistent with local gravity constraints under the chameleon mechanism, while at the same time satisfying conditions for the cosmological viability. We present a number of viable f(R) models that satisfy cosmological and local gravity constraints. We also study a class of scalar-tensor dark energy models based on Brans-Dicke theory with a scalar-field potential. The action in the Einstein frame can be viewed as a coupled quintessence scenario with a constant coupling Q that is related to a Brans-Dicke parameter via . We show that, even when is of the order of 1, it is possible for these models to be consistent with cosmological and local gravity constraints as long as the field potential is designed in a suitable way. We investigate the evolution of matter density perturbations for f(R) and scalar-tensor models and show that model parameters as well as the strength of the coupling Q can be constrained from matter/CMB power spectra due to the enhanced growth rate of perturbations compared to the ΛCDM model. Finally, we discuss the DGP braneworld model as a candidate for dark energy. While the late-time cosmic acceleration is possible, this model is under strong pressure from joint constraints using the data of SNLS, BAO, and the CMB shift parameter. Moreover, a ghost mode is present for such a self-accelerating universe. Thus the original DGP model is effectively ruled out from observational constraints as well as from the ghost problem.

本文言語English
ページ(範囲)99-145
ページ数47
ジャーナルLecture Notes in Physics
800
DOI
出版ステータスPublished - 2010
外部発表はい

ASJC Scopus subject areas

  • 物理学および天文学(その他)

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