分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： The possibility of reconstructing a spherically symmetric inhomogeneous Lemaitre-Tolman-Bondi (LTB) model with Lambda CDM observations has drawn much attention. Recently, an inhomogeneous LTB model having the same luminosity-distance and light-cone mass density of the homogeneous Lambda CDM model was reconstructed. From the Wilkinson microwave anisotropy probe 7-year measurements together with other cosmological observations, we calculate the cosmic age at our position in this LTB model, and obtain a constraint t(LTB) < 11.7 Gyr at 1 sigma confidence level. We find that this result is, although 2 Gyr younger compared with the age of the homogeneous Lambda CDM model, still within 1 sigma agreement with the constraint of cosmic age given by current astronomical measurements. We expect that in the future, with the help of more advanced observations, we can distinguish the reconstructed inhomogeneous LTB model from the homogeneous Lambda CDM model.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： We investigate the cosmic age problem associated with 9 extremely old globular clusters in M31 galaxy and 1 very old high-z quasar automatic plate-measuring machine 08279 + 5255 at z = 3.91. These 9 globular clusters have not been used to study the cosmic age problem in the previous literature. By evaluating the age of the Universe in the Lambda cold dark matter model with the observational constraints from the Type Ia supernovae, the baryon acoustic oscillations, the cosmic microwave background, and the independent H-0 measurements, we find that the existence of 5 globular clusters and 1 high-z quasar are in tension (over 2 sigma confidence level) with the current cosmological observations. So if the age estimates of these objects are correct, the cosmic age puzzle still remains in the standard cosmology. Moreover, we extend our investigations to the cases of the interacting dark energy models. It is found that although the introduction of the interaction between dark sectors can give a larger cosmic age, the interacting dark energy models still have difficulty to pass the cosmic age test.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： In this paper we investigate the possible direct, non-gravitational interaction between holographic dark energy (HDE) and dark matter. Firstly, we start with two simple models with the interaction terms Q proportional to rho(dm) and Q proportional to rho(de), and then we move on to the general form Q proportional to rho(alpha)(m)rho(beta)(de). The cosmological constraints of the models are obtained from the joint analysis of the present Union 2.1+BAO+CMB+H-0 data. We find that the data slightly favor an energy flow from dark matter to dark energy, although the original HDE model still lies in the 95.4% confidence level (CL) region. For all models we find c -1. We show that this solution cannot be accomplished in the two simple models, while for the general model such a solution can be achieved with a large beta, and the big rip may be avoided at the 95.4% CL.
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