
New initial condition of the new agegraphic dark energy model
Li YunHe (李云鹤), Zhang JingFei (张敬飞), Zhang Xin (张鑫)
Chin. Phys. B, 2013, 22 (3):
039501.
DOI: 10.1088/16741056/22/3/039501
The initial condition Ω_{de}(z_{ini})=n^{2}(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 singleparameter darkenergy 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 matterdominated and the radiationdominated epochs, and obtain a new initial condition Ω_{de}(z_{ini})=n^{2}(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 singleparameter 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.
