### Abstract

We construct a family of viable scalar-tensor models of dark energy (DE) which possess a phase of late-time acceleration preceded by a standard matter era, while at the same time satisfying the local gravity constraints (LGC). The coupling Q between the scalar field and the nonrelativistic matter in the Einstein frame is assumed to be constant in our scenario, which is a generalization of f(R) gravity theories corresponding to the coupling Q=-1/6. We find that these models can be made compatible with local gravity constraints even when |Q| is of the order of unity through a chameleon mechanism, if the scalar-field potential is chosen to have a sufficiently large mass in the high-curvature regions. We show that these models generally lead to the divergence of the equation of state of DE, which occurs at smaller redshifts as the deviation from the ΛCDM model becomes more significant. We also study the evolution of matter density perturbations and employ them to place bounds on the coupling |Q| as well as model parameters of the field potential from observations of the matter power spectrum and the cosmic microwave background (CMB) anisotropies. We find that, as long as |Q| is smaller than the order of unity, there exist allowed parameter regions that are consistent with both observational and local gravity constraints.

Original language | English |
---|---|

Article number | 103009 |

Journal | Physical Review D - Particles, Fields, Gravitation and Cosmology |

Volume | 77 |

Issue number | 10 |

DOIs | |

Publication status | Published - 2008 May 21 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Physics and Astronomy(all)
- Nuclear and High Energy Physics
- Mathematical Physics

### Cite this

*Physical Review D - Particles, Fields, Gravitation and Cosmology*,

*77*(10), [103009]. https://doi.org/10.1103/PhysRevD.77.103009

**Constraints on scalar-tensor models of dark energy from observational and local gravity tests.** / Tsujikawa, Shinji; Uddin, Kotub; Mizuno, Shuntaro; Tavakol, Reza; Yokoyama, Jun'Ichi.

Research output: Contribution to journal › Article

*Physical Review D - Particles, Fields, Gravitation and Cosmology*, vol. 77, no. 10, 103009. https://doi.org/10.1103/PhysRevD.77.103009

}

TY - JOUR

T1 - Constraints on scalar-tensor models of dark energy from observational and local gravity tests

AU - Tsujikawa, Shinji

AU - Uddin, Kotub

AU - Mizuno, Shuntaro

AU - Tavakol, Reza

AU - Yokoyama, Jun'Ichi

PY - 2008/5/21

Y1 - 2008/5/21

N2 - We construct a family of viable scalar-tensor models of dark energy (DE) which possess a phase of late-time acceleration preceded by a standard matter era, while at the same time satisfying the local gravity constraints (LGC). The coupling Q between the scalar field and the nonrelativistic matter in the Einstein frame is assumed to be constant in our scenario, which is a generalization of f(R) gravity theories corresponding to the coupling Q=-1/6. We find that these models can be made compatible with local gravity constraints even when |Q| is of the order of unity through a chameleon mechanism, if the scalar-field potential is chosen to have a sufficiently large mass in the high-curvature regions. We show that these models generally lead to the divergence of the equation of state of DE, which occurs at smaller redshifts as the deviation from the ΛCDM model becomes more significant. We also study the evolution of matter density perturbations and employ them to place bounds on the coupling |Q| as well as model parameters of the field potential from observations of the matter power spectrum and the cosmic microwave background (CMB) anisotropies. We find that, as long as |Q| is smaller than the order of unity, there exist allowed parameter regions that are consistent with both observational and local gravity constraints.

AB - We construct a family of viable scalar-tensor models of dark energy (DE) which possess a phase of late-time acceleration preceded by a standard matter era, while at the same time satisfying the local gravity constraints (LGC). The coupling Q between the scalar field and the nonrelativistic matter in the Einstein frame is assumed to be constant in our scenario, which is a generalization of f(R) gravity theories corresponding to the coupling Q=-1/6. We find that these models can be made compatible with local gravity constraints even when |Q| is of the order of unity through a chameleon mechanism, if the scalar-field potential is chosen to have a sufficiently large mass in the high-curvature regions. We show that these models generally lead to the divergence of the equation of state of DE, which occurs at smaller redshifts as the deviation from the ΛCDM model becomes more significant. We also study the evolution of matter density perturbations and employ them to place bounds on the coupling |Q| as well as model parameters of the field potential from observations of the matter power spectrum and the cosmic microwave background (CMB) anisotropies. We find that, as long as |Q| is smaller than the order of unity, there exist allowed parameter regions that are consistent with both observational and local gravity constraints.

UR - http://www.scopus.com/inward/record.url?scp=44349135049&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=44349135049&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.77.103009

DO - 10.1103/PhysRevD.77.103009

M3 - Article

AN - SCOPUS:44349135049

VL - 77

JO - Physical review D: Particles and fields

JF - Physical review D: Particles and fields

SN - 0556-2821

IS - 10

M1 - 103009

ER -