English

Structure formation in the DGP cosmological model

Astrophysics 2009-11-13 v1 General Relativity and Quantum Cosmology High Energy Physics - Theory

Abstract

The DGP brane-world model provides an alternative to the standard LCDM cosmology, in which the late universe accelerates due to a modification of gravity rather than vacuum energy. The cosmological constant Λ\Lambda in LCDM is replaced by a single parameter, the crossover scale rcr_c, in DGP. The Supernova redshift observations can be fitted by both models, with ΛH02\Lambda\sim H_0^2 and rcH01r_c \sim H_0^{-1}. This degeneracy is broken by structure formation, which is suppressed in different ways in the two models. There is some confusion in the literature about how the standard linear growth factor is modified in DGP. While the luminosity distance can be computed purely from the modified 4-dimensional Friedman equation, the evolution of density perturbations requires an analysis of the 5-dimensional gravitational field. We show that if the 5-dimensional effects are inappropriately neglected, then the 4-dimensional Bianchi identities are violated and the computed growth factor is incorrect. By using the 5-dimensional equations, we derive the correct growth factor.

Keywords

Cite

@article{arxiv.astro-ph/0511634,
  title  = {Structure formation in the DGP cosmological model},
  author = {Kazuya Koyama and Roy Maartens},
  journal= {arXiv preprint arXiv:astro-ph/0511634},
  year   = {2009}
}

Comments

6 pages, 2 figures