Constraints on modified Chaplygin gas from large scale structure

Abstract

We study cosmological models with modified Chaplygin gas (in short, MCG) to determine observational constraints on its EoS parameters. The observational data of the background and the growth tests are employed. The background test data namely, H(z) − z data, CMB shift parameter, Baryonic acoustic oscillations (BAO) peak parameter, SN Ia data are considered to study the dynamical aspects of the universe. The growth test data we employ here consists of the linear growth function for the large scale structures of the universe, models are explored assuming MCG as a candidate for dark energy. Considering the observational growth data for a given range of redshift from the Wiggle-Z measurements and rms mass fluctuations from Ly-α measurements, cosmological models are analyzed numerically to determine constraints on the MCG parameters. In this case, the Wang-Steinhardt ansatz for the growth index γ and growth function f (defined as f = Ω γ m (a)) are also taken into account for the numerical analysis. The best-fit values of the equation of state parameters obtained here are used to study the variation of the growth function (f ), growth index (γ), equation of state parameter (ω), squared sound speed c 2 s and deceleration parameter with redshift z. The observational constraints on the MCG parameters obtained here are then compared with those of the GCG model for viable cosmology. It is noted that MCG models satisfactorily accommodate an accelerating phase followed by a matter dominated phase of the universe. The permitted range of values of the EoS parameters and the associated parameters (f , γ, ω, Ω, c 2 s , q) are compared with those obtained earlier using other observations.

On the concordance of cosmological data in the case of the generalized Chaplygin gas

“…−0.25 [26] and the 1σ interval α ∈ [0.08, 0.31] [27], should be of the order of those expected in the generalised Chaplygin gas. Their CMB analysis also makes use of the shift parameter R.…”

“…As a modification of the generalised Chaplygin gas, the equation of state p = βρ − A/ρ α is proposed, but it is found in [26,27] that β has to be very small. Thus, both the energy density and the equation of state approach those of the generalised Chaplygin gas.…”

“…This generated again a large interest in the Chaplygin cosmologies and its variants, see e. g. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Most papers assume a flat universe when the allowed parameter space is estimated according to various cosmological data.…”

Impact of generalized dissipative coefficient on warm inflationary dynamics in the light of latest Planck data

“…(6), the energy density of the MCG is characterized by three parameters, B s (or equivalently B), A, and λ. Particularly, in [84] by using a joint analysis of several tests at background as well as perturbative level, as the differential age of old galaxies, given by H (z), baryonic acoustic oscillations (BAO) peak parameter, CMB shift parameter, SN Ia data, and growth index, the values for the best fit (with χ 2 /d.o. f ∼ 1.0296) are given by B s = 0.8252, A = 0.0046, and λ = 0.1905.…”

“…1 show the ratios T /H and /3H as a functions of the scalar spectral index n s for the case m = 3, i.e., (φ, T ) = C φ T 3 /φ 2 , respectively. To obtain both plots we used three different values for C φ parameter and considered the following values characterizing the MCG: A = 0.0046, B = 0.8289 (by fixing ρ mcg0 = 1), and λ = 0.1905 [84], and C γ = 70. In order to obtain numerical values for T /H and /H , for each value of C φ we solve numerically Eqs.…”