Phenomenology in type-I minimally modified gravity

Katsuki Aoki, Antonio De Felice, Chunshan Lin, Shinji Mukohyama, Michele Oliosi

    Research output: Contribution to journalArticle

    5 Citations (Scopus)

    Abstract

    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.

    Original languageEnglish
    Article number017
    JournalJournal of Cosmology and Astroparticle Physics
    Volume2019
    Issue number1
    DOIs
    Publication statusPublished - 2019 Jan 7

    ASJC Scopus subject areas

    • Astronomy and Astrophysics

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