Jianbo Lu

Constraints on modified Chaplygin gas from recent observations and a comparison of its status with other models

Abstract In this Letter, a modified Chaplygin gas (MCG) model of unifying dark energy and dark matter with the exotic equation of state p MCG = B ρ MCG − A ρ MCG α is constrained from recently observed data: the 182 Gold SNe Ia, the 3-year WMAP and the SDSS baryon acoustic peak. It is shown that the best fit value of the three parameters ( B , B s , α ) in MCG model are ( − 0.085 , 0.822 , 1.724 ). Furthermore, we find the best fit w ( z ) crosses −1 in the past and the present best fit value w ( 0 ) = − 1.114 − 1 , and the 1σ confidence level of w ( 0 ) is − 0.946 ⩽ w ( 0 ) ⩽ − 1.282 . Finally, we find that the MCG model has the smallest χ min 2 value in all eight given models. According to the Akaike Information Criterion (AIC) of model selection, we conclude that recent observational data support the MCG model as well as other popular models.

Observational constraints on holographic dark energy with varying gravitational constant

We use observational data from Type Ia Supernovae (SN), Baryon Acoustic Oscillations (BAO), Cosmic Microwave Background (CMB) and observational Hubble data (OHD), and the Markov Chain Monte Carlo (MCMC) method, to constrain the cosmological scenario of holographic dark energy with varying gravitational constant. We consider both flat and non-flat background geometry, and we present the corresponding constraints and contour-plots of the model parameters. We conclude that the scenario is compatible with observations. In 1σ we find ΩΛ0 = 0.72+0.03−0.03, Ωk0 = −0.0013+0.0130−0.0040, c = 0.80+0.19−0.14 and ΔG≡G/G = −0.0025+0.0080−0.0050, while for the present value of the dark energy equation-of-state parameter we obtain w0 = −1.04+0.15−0.20.

Holographic dark energy in Brans–Dicke theory

AbstractIn this paper, the holographic dark-energy model is considered in Brans–Dicke theory, where the holographic dark-energy density ρΛ=3c2Mpl2L−2 is replaced by ρh=3c2Φ(t)L−2. Here n

Observational constraint on generalized Chaplygin gas model

varPhi (t)=frac{1}{8pi G}

Cosmic Constraint on Ricci Dark Energy Model

nis the time-variable Newton constant. With this replacement, it is found that no accelerated expansion for the universe will be achieved when the Hubble horizon is taken to play the role of an IR cut-off. When the event horizon is adopted as the IR cut-off, accelerated expansion for the universe is obtained. In this case, the equation of state of holographic dark energy, wh, takes the modified form n

Cosmological constraints on generalized Chaplygin gas model: Markov Chain Monte Carlo approach

w_{mathrm{h}}=-frac{1}{3}(1+alpha+frac{2}{c}sqrt{ varOmega _{mathrm{h}}})

Constraints on kinematic model from recent cosmic observations: SN Ia, BAO and observational Hubble data

n. In the limit α→0, the ‘standard’ holographic dark energy is recovered. In the holographic dark-energy dominated epoch, power-law and de Sitter time-space solutions are obtained.

Constraints on accelerating universe using ESSENCE and Gold supernovae data combined with other cosmological probes

We investigate observational constraints on the generalized Chaplygin gas (GCG) model as the unification of dark matter and dark energy from the latest observational data: the Union SNe Ia data, the observational Hubble data, the SDSS baryon acoustic peak and the five-year WMAP shift parameter. The result is obtained that the best-fit values of the GCG model parameters with their confidence level are As=0.73−0.06+0.06 (1σ) −0.09+0.09 (2σ), α=−0.09−0.12+0.15 (1σ) −0.19+0.26 (2σ). Furthermore, in this model, we can see that the evolution of equation of state (EOS) for dark energy is similar to quiessence, and its current best-fit value is w0de=−0.96 with the 1σ confidence level −0.91≥w0de≥−1.00.

The influence of free quintessence on gravitational frequency shift and deflection of light with 4D momentum

In this paper, a holographic dark energy model, dubbed Ricci dark energy, is confronted with cosmological observational data from type Ia Supernovae (SN Ia), baryon acoustic oscillations (BAO) and cosmic microwave background (CMB). By using maximum likelihood method, we found that Ricci dark energy model is a viable candidate of dark energy model with the best fit parameters: Ωm0 = 0.34 ± 0.04, α = 0.38 ± 0.03 with 1σ error. Here, α is a dimensionless parameter related to Ricci dark energy ρR and Ricci scalar R, i.e. ρR ∝ αR.

Holographic p-wave superfluid

We use the Markov Chain Monte Carlo method to investigate a global constraints on the generalized Chaplygin gas (GCG) model as the unification of dark matter and dark energy from the latest observational data: the Constitution dataset of type supernovae Ia (SNIa), the observational Hubble data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the cosmic microwave background (CMB) data. In a non-flat universe, the constraint results for GCG model are, Ωbh2 = 0.0235+0.0021−0.0018 (1σ) +0.0028−0.0022 (2σ), Ωk = 0.0035+0.0172−0.0182 (1σ) +0.0226−0.0204 (2σ), As = 0.753+0.037−0.035 (1σ) +0.045−0.044 (2σ), α = 0.043+0.102−0.106 (1σ) +0.134−0.117 (2σ), and H0 = 70.00+3.25−2.92 (1σ) +3.77−3.67 (2σ), which is more stringent than the previous results for constraint on GCG model parameters. Furthermore, according to the information criterion, it seems that the current observations much support ΛCDM model relative to the GCG model.