Busti, V. C. 2011 GRB和SN Ia限制宇宙学参数

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Title:		Constraining the dark energy and smoothness parameter with SNe Ia and Gamma-Ray Bursts
Authors:		Busti, V. C.; Santos, R. C.; Lima, J. A. S.
Publication:		eprint arXiv:1202.0449
Publication Date:		02/2012
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics, General Relativity and Quantum Cosmology
Comment:		7 pages, 4 figures
Bibliographic Code:		2012arXiv1202.0449B

Abstract

The existence of inhomogeneities in the observed Universe modifies the distance-redshift relations thereby affecting the results of cosmological tests in comparison to the ones derived assuming spatially uniform models. By modeling the inhomogeneities through a generalized Zeldovich-Kantowski-Dyer-Roeder (ZKDR) approach which is phenomenologically characterized by a smoothness parameter $\alpha$, we rediscuss the constraints on the cosmic parameters based on Supernovae type Ia and Gamma-Ray Bursts (GRBs) data. The present analysis is restricted to a flat $\Lambda$CDM model with the reasonable assumption that $\Lambda$ does not clump. A $\chi^{2}$-analysis using 557 SNe Ia data from the Union2 Compilation Data (Amanullah {\it et al.} 2010) constrains the pair of parameters ($\Omega_m, \alpha$) to $\Omega_m=0.27_{-0.03}^{+0.08}$($2\sigma$) and $\alpha \geq 0.25$. A similar analysis based only on 59 Hymnium GRBs (Wei 2010) constrains the matter density parameter to be $\Omega_m= 0.35^{+0.62}_{-0.24}$ ($2\sigma$) while all values for the smoothness parameter are allowed. By performing a joint analysis, it is found that $\Omega_m = 0.27^{+0.06}_{-0.03}$ and $\alpha \geq 0.52$. As a general result, although considering that current GRB data alone cannot constrain the smoothness $\alpha$ parameter our analysis provides an interesting cosmological probe for dark energy even in the presence of inhomogeneities.

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