Abstract
We study second-order cosmological perturbations in scalar-tensor models of dark energy that satisfy local gravity constraints, including f(R) gravity. We derive equations for matter fluctuations under a sub-horizon approximation and clarify conditions under which first-order perturbations in the scalar field can be neglected relative to second-order matter and velocity perturbations. We also compute the skewness of the matter density distribution and find that the difference from the ΛCDM (CDM: cold dark matter) model is less than a few per cent even if the growth rate of first-order perturbations is significantly different from that in the ΛCDM model. This shows that the skewness provides a model-independent test for the picture of gravitational instability from Gaussian initial perturbations including scalar-tensor modified gravity models.
Original language | English |
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Article number | 009 |
Journal | Journal of Cosmology and Astroparticle Physics |
Volume | 2008 |
Issue number | 9 |
DOIs | |
Publication status | Published - 2008 Sep 1 |
Externally published | Yes |
Keywords
- Cosmological perturbation theory
- Dark energy theory
ASJC Scopus subject areas
- Astronomy and Astrophysics