We use the Monte-Carlo Markov Chain method to explore the dark energy property and the cosmic curvature by fitting two popular dark energy parameterizations to the observational data. The new 182 gold supernova Ia data and the ESSENCE data both give good constraint on the DE parameters and the cosmic curvature for the dark energy model $w_0+w_a z/(1+z)$. The cosmic curvature is found to be $|Ω_k|\la 0.03$. For the dark energy model $w_0+w_a z/(1+z)^2$, the ESSENCE data gives better constraint on the cosmic curvature and we get $|Ω_k|\leq 0.02$.
Observational Constraints on Dark Energy and Cosmic Curvature
Current observational bounds on dark energy depend on assumptions about the curvature of the universe. We present a simple and efficient method for incorporating constraints from CMB anisotropy data, and use it to derive constraints on cosmic curvature and dark energy density as a free function of cosmic time using current data. We show that there are two CMB shift parameters, R=sqrt{Ω_m H_0^2} r( z_{CMB} ) (scaled distance to recombination) and l_a=πr( z_{CMB} )/r_s( z_{CMB} )(angular scale of the sound horizon at recombination), with measured values that are nearly uncorrelated with each oth…
Scale Factor Dependent Equations of State for Curvature Inspired Dark Energy, Phantom Barrier and Late Cosmic Acceleration
在这里，我们发现如果在Einstein-Hilbert拉氏量中加入标量曲率的非线性项，那么暗能量和暗物质将从引力扇区中产生。暗能量的状态方程，具有形式$p_{\rm de} = - ρ_{\rm de} + f(a) (with $ p_{\rm de}（ρ_{ \rm de}）$ being the pressure(density) for dark energy, $ f（a）$ being a function of scale feactor $ a（t）$ and $ t $ being the cosmic time) is explored. Interestingly, this equation of state leads to a phantom barrier $ {\rm w}_{ \rm de} = \rm MATHABMN/ρ_{ \rm de} =-1 $ at $ a = a_{\rm w} $. It is found that when $ a < a_{\rm w}，{ \rm w}_{\rm de} > - 1 $ and $ { \rm w}_{ \rm de} < - 1 $ for $ a >a_{\rm w}，$ showing a transition from non-phantom to phantom phas…
