Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-09-24
Phys.Rev.D80:121301,2009
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
references added, accepted for publication in PRD, 5 pages, 4 figures
Scientific paper
10.1103/PhysRevD.80.121301
We present a cosmological model with a solution that self-accelerates at late-times without signs of ghost instabilities on small scales. The model is a natural extension of the Brans-Dicke (BD) theory including a non-linear derivative interaction, which appears in a theory with the Galilean shift symmetry. The existence of the self-accelerating universe requires a negative BD parameter but, thanks to the non-linear term, small fluctuations around the solution are stable on small scales. General relativity is recovered at early times and on small scales by this non-linear interaction via the Vainshtein mechanism. At late time, gravity is strongly modified and the background cosmology shows a phantom-like behaviour and the growth rate of structure formation is enhanced. Thus this model leaves distinct signatures in cosmological observations and it can be distinguished from standard $\Lambda$CDM cosmology.
Koyama Kazuya
Silva Fabio P.
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