Modified Chaplygin gas as a unified dark matter and dark energy model and cosmic constraints

Abstract

A modified Chaplygin gas model (MCG), ρMCG/ρMCG0 = [Bs + (1 − Bs)a −3(1+B)(1+α) ] 1/(1+α) , as a unified dark matter model and dark energy model is constrained by using current available cosmic observational data points which include type Ia supernovae, baryon acoustic oscillation and the seventh year full WMAP data points. As a contrast to the consideration in the literatures, we do not separate the MCG into two components, i.e. dark mater and dark energy component, but we take it as a whole energy component-a unified dark sector. By using Markov Chain Monte Carlo method, a tight constraint is obtained: α = 0.000727 +0.00142+0.00391 −0.00140−0.00234 , B = 0.000777 +0.000201+0.000915 −0.000302−0.000697 and Bs = 0.782 +0.0163+0.0307 −0.0162−0.0329 .

Constraints on the dark matter sound speed from galactic scales: The cases of the modified and extended Chaplygin gas

“…(10) is much more stringent than those obtained using the CMB or BAO (see, e.g., [32]). Here we shall explain why.…”

“…This model incorporates an extra parameter which is associated to a lower bound on the sound speed of the effective DM component. The MCG has been observationally constrained using the redshift dependence of the apparent magnitude of type Ia supernovae, the Cosmic Microwave Background (CMB) anisotropies, and the matter power spectrum, including Baryonic Acoustic Oscillations (BAO) [25][26][27][28][29][30][31][32][33][34]. Further extensions incorporating additional terms accounting for a possible growth of the comoving Jeans length with cosmic density have also been proposed in the literature (see, e.g., [35]).…”

Stability of effective thin-shell wormholes under Lorentz symmetry breaking supported by dark matter and dark energy

“…(3, 5, 7). Now, we use the EOS of MCG as a unified DE and DM, which is known as a dark sector, can be cast into [36,61,62] …”

“…The MCG model has two components: DM is presented by a −3 and the remaining part is DE. The best-fit values for this model according to the seventh-year Wilkinson microwave anisotropy probe (WMAP) and the sloan digital sky survey (SDSS)'s baryon oscillation spectroscopic survey (BAO) are as follows: B s = 0.822, α = 1.724 and B = −0.085 [36,78]. There are further constraints from the cosmic microwave background (CMB) shift parameters (BAO, type Ia supernova data (SN Ia)), observational Hubble data, and cluster X-ray gas mass fraction (CBF) as follows: B s = 0.7788 −0.00915 (2σ).…”

Testing the Interacting Dark Energy Model with Cosmic Microwave Background Anisotropy and Observational Hubble Data

“…In [16][17][18], the unified dark fluid with constant adiabatic sound speed α was tested by the cosmic microwave background (CMB) from WMAP7 (WMAP 7-year data) [19], baryon acoustic oscillation (BAO), type Ia supernovae (SNIa), the results showed a very small value of adiabatic sound speed, the order was about 10 −3 in 1σ region. Another kind of unified model is the Chaplygin gas model and its generalized model, such as generalized Chaplygin gas, modified Chaplygin gas and so on, several work have been done to constrain the model parameter space of series of Chaplygin gas models [20][21][22][23], in [22], the model parameters of generalized Chaplygin gas were shown, α = 0.00126 not favor the phenomenon of fast transition of equation of state for the unified dark fluid model [24]. Moreover, when one considered the viscous effects in the Chaplygin gas model, the bulk viscosity coefficient parameter was constrained in the order of 10 −5 [25,26].…”