J. A. S. Lima, V. C. Busti, R. C. Santos
A new interpretation of the conventional Dyer-Roeder (DR) approach by allowing light received from distant sources to travel in regions denser than average is proposed. It is argued that the existence of a distribution of small and moderate cosmic voids (or "black regions") implies that its matter content was redistributed to the homogeneous and clustered matter components with the former becoming denser than the cosmic average in the absence of voids. Phenomenologically, this means that the DR smoothness parameter (denoted here by alpha_E) can be greater than unity, and, therefore, all previous analyses constraining it should be rediscussed with a free upper limit. Accordingly, by performing a statistical analysis involving 557 type Ia supernovae (SNe Ia) from Union2 compilation data in a flat LCDM model we obtain for the extended parameter, alpha_E=1.26^{+0.68}_{-0.54} (1sigma). The effects of alpha_E are also analyzed for generic LCDM models and flat XCDM cosmologies. For both models, we find that a value of alpha_E greater than unity is able to harmonize SNe Ia and cosmic microwave background (CMB) observations thereby alleviating the well known tension between low and high redshift data. Finally, a simple toy model based on the existence of cosmic voids is proposed in order to justify why alpha_E can be greater than unity as required by Supernovae data.
View original:
http://arxiv.org/abs/1301.5360
No comments:
Post a Comment