Open AccessLarge‐scale structure in non‐standard cosmologies
Author(s) -
Multamäki Tuomas,
Gaztañaga Enrique,
Manera Marc
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06880.x
Subject(s) - physics , cosmic microwave background , dark energy , polytropic process , skewness , redshift , astrophysics , amplitude , cosmic variance , cosmology , metric expansion of space , statistical physics , statistics , quantum mechanics , galaxy , mathematics , anisotropy
We study the growth of large‐scale structure in two recently proposed non‐standard cosmological models: the ‘brane’ induced gravity model of Dvali, Gabadadze and Porrati (DGP) and the ‘Cardassian’ models of Freese and Lewis. A general formalism for calculating the growth of fluctuations in models with a non‐standard Friedman equation and a normal continuity equation of energy density is discussed. Both linear and non‐linear growth are studied, together with their observational signatures on higher‐order statistics and abundance of collapsed objects. In general, models that show similar cosmic acceleration at z ≃ 1 can produce quite different normalization for large‐scale density fluctuations, i.e. σ 8 , cluster abundance or higher‐order statistics, such as the normalized skewness S 3 , which is independent of the linear normalization. For example, for a flat universe with Ω M ≃ 0.22 , DGP and standard Cardassian cosmologies predict about two and three times more clusters respectively than the standard Λ model at z = 1.5 . When normalized to cosmic microwave background fluctuations, the σ 8 amplitude turns out to be lower by a few tens of per cent. We also find that, for a limited redshift range, the linear growth rate can be faster in some models (e.g. modified polytropic Cardassian with q > 1 ) than in the Einstein–de Sitter universe. The value of the skewness S 3 is found to have up to ≃10 per cent variations (up or down) from model to model.