科研之友
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摘要
Motivated by the increasing evidence for the need of a geometry that resembles Bianchi morphology to explain the observed anisotropy in the WMAP data, we have discussed some features of the Bianchi type universes in the presence of a fluid that wields an anisotropic equation of state (EoS) parameter in general relativity. Such models are of great interest in cosmology in favor of constructing more realistic models than FLRW models with maximally symmetric spatial geometry. Additionally, the interest in such models was promoted in recent years due to the debate that going on the analysis and the interpretation of the WMAP [21, 111, 112] data, whether they need a Bianchi type morphology to be explained successfully [7, 103, 118, 117]. The LLC-WMAP data maps show seven axes well aligned with one another and the direction Virgo. For this reason Bianchi models are important in the study of anisotropies. In the present study of Bianchi type-I, II, III, V and VI (0) space-times, we observe that the EoS for dark energy omega is found to be time-dependent and its existing range for derived models is in good agreement with the recent observations of SNe Ia data [50], SNe Ia data with CMBR anisotropy and galaxy clustering statistics [11] and latest combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift type Ia supernovae and galaxy clustering [21, 51]. It has been suggested that the dark energy that explains the observed accelerating expansion of the universe may arise due to the contribution to the vacuum energy of the EoS in a time dependent background. The cosmological constant I > is found to be a positive decreasing function of time and it approaches to a small positive value at late time (i.e. the present epoch) which is corroborated by results from recent type Ia supernovae observations.
- 出版日期2015-5
