New initial condition of the new agegraphic dark energy model

The initial condition Ω_de(z_ini)=n²(1+z_ini)^-2/4 at z_ini=2000 widely used to solve the differential equation of the density of the new agegraphic dark energy (NADE) Ω_de, makes the NADE model be a single-parameter dark-energy cosmological model. However, we find that this initial condition is only applicable in a flat universe with only dark energy and pressureless matter. In fact, in order to obtain more information from current observational data, such as the cosmic microwave background (CMB) and the baryon acoustic oscillations (BAO), we need to consider the contribution of radiation. For this situation, the initial condition mentioned above becomes invalid. To overcome this shortage, we investigate the evolutions of dark energy in the matter-dominated and the radiation-dominated epochs, and obtain a new initial condition Ω_de(z_ini)=n²(1+z_ini)^-2(1+√F(z_ini)²/4 at z_ini=2000, where F(z)≡Ω_r0(1+z)/[Ω_m0+Ω_r0(1+z)] with Ω_r0 and Ω_m0 being the current density parameters of radiation and pressureless matter, respectively. This revised initial condition is applicable for the differential equation of Ω_de obtained in the standard Friedmann-Robertson-Walker (FRW) universe with dark energy, pressureless matter, radiation, and even spatial curvature, and can still keep the NADE model being a single-parameter model. With the revised initial condition and the observational data of type Ia supernova (SNIa), CMB, and BAO, we finally constrain the NADE model. The results show that the single free parameter n of the NADE model can be constrained tightly.     

Prospect for Cosmological Parameter Estimation Using Future Hubble Parameter Measurements

We constrain cosmological parameters using only Hubble parameter data and quantify the impact of future Hubble parameter measurements on parameter estimation for the most typical dark energy models. We first constrain cosmological parameters using 52 current Hubble parameter data including the Hubble constant measurement from the Hubble Space Telescope. Then we simulate the baryon acoustic oscillation signals from WFIRST(Wide-Field Infrared Survey Telescope) covering the redshift range of z ∈ [0.5, 2] and the redshift drift data from E-ELT(European Extremely Large Telescope) in the redshift range of z ∈ [2, 5]. It is shown that solely using the current Hubble parameter data could give fairly good constraints on cosmological parameters. Compared to the current Hubble parameter data, with the WFIRST observation the H(z) constraints on dark energy would be improved slightly, while with the E-ELT observation the H(z) constraints on dark energy is enormously improved.     

非平宇宙中的全息精质模型

提出了非平宇宙中的全息精质模型,构造出精质标量场,对全息暗能量的宇宙学演化进行有效描述.推导了全息暗能量在非平宇宙中的演化方程,进一步通过与正则标量场建立对应,构造出全息精质标量场模型,并讨论了空间曲率对模型的影响.结果表明,空间曲率对标量场演化的影响主要表现在高红移区域,而对于重构出的标量场势函数,在标量场值越小的区域空间曲率的影响越大.     

Statefinder Diagnosis for the Extended Holographic Ricci Dark Energy Model without and with Interaction

We apply the statefinder diagnostic to the extended holographic Ricci dark energy (ERDE) model without and with interaction to study their behaviors. We plot the trajectories of various parameters for different cases. It is shown that the non-interacting model does not reach the LCDM point {1, 0 } and the interacting one is favored, because the interaction makes the evolution of the statefinder pair r, s quite different.     

Reconstructing Quintom from WMAP 5-year Observations： Generalized Ghost Condensate

In the 5-year WMAP data analysis, a new parametrization form for dark energy equation-of-state was used, and it has been shown that the equation-of-state, w（z）, crosses the cosmological-constant boundary w = -1. Based on this observation, in this paper, we investigate the reconstruction of quintom dark energy model. As a single-real-sealarfield model of dark energy, the generalized ghost condensate model provides us with a successful mechanism for realizing the quintom-like behavior. Therefore, we reconstruct this scalar-field quintom dark energy model from the WMAP 5-year observational results. As a comparison, we also discuss the quintom reconstruction based on other specific dark energy ansatzs, such as the CPL parametrization and the holographic dark energy scenarios.     

Joint constraints on cosmological parameters using future multi-band gravitational wave standard siren observations

Gravitational waves(GWs) from compact binary coalescences can be used as standard sirens to explore the cosmic expansion history. In the next decades, it is anticipated that we could obtain the multi-band GW standard siren data(from nanohertz to a few hundred hertz), which are expected to play an important role in cosmological parameter estimation. In this work, we provide, for the first time to the best of our knowledge, joint constraints on cosmological parameters using the future multi-band G...