## 抄録

We study cosmology in a class of minimally modified gravity (MMG) with two local gravitational degrees of freedom. We classify modified gravity theories into type-I and type-II: theories of type-I have an Einstein frame and can be recast by change of variables as general relativity (GR) with a non-minimal matter coupling, while theories of type-II have no Einstein frame. Considering a canonical transformation of the lapse, the 3-dimensional induced metric and their conjugate momenta we generate type-I MMG. We then show that phenomenological deviations from GR, such as the speed of gravitational waves c
_{T}
and the effective gravitational constant for scalar perturbations G
_{eff}
, are characterized by two functions of an auxiliary variable. We study the phenomenology of several models all having c
_{T}
=1. We obtain a scenario with c
_{T}
=1 in which the effective equation-of-state parameter of dark energy is different from -1 even though the cosmic acceleration is caused by a bare cosmological constant, and we find that it is possible to reconstruct the theory on choosing a selected time-evolution for the effective dark energy component.

本文言語 | English |
---|---|

論文番号 | 017 |

ジャーナル | Journal of Cosmology and Astroparticle Physics |

巻 | 2019 |

号 | 1 |

DOI | |

出版ステータス | Published - 2019 1月 7 |

## ASJC Scopus subject areas

- 天文学と天体物理学