Studying light propagation in a locally homogeneous universe through an extended Dyer-Roeder approach

Abstract

Light is affected by local inhomogeneities in its propagation, which may alter distances and so cosmological parameter estimation. In the era of precision cosmology, the presence of inhomogeneities may induce systematic errors if not properly accounted. In this vein, 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 $\Lambda$CDM model we obtain for the extended parameter, ${\alpha }_E=1.26_{-0.54}^{+0.68}$ ($1\sigma$). The effects of ${\alpha }_E$ are also analyzed for generic $\Lambda$CDM 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 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.

5 pages, 2 figures. Title modified, results unchanged. It matches version published as a Brief Report in Phys. Rev. D

References in corpus (10)

• Spectra and Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation
• A general test of the Copernican Principle
• A public void catalog from the SDSS DR7 Galaxy Redshift Surveys based on the watershed transform
• Testing the Distance-Duality Relation with Galaxy Clusters and Type Ia Supernovae
• The blackness of the cosmic microwave background spectrum as a probe of the distance-duality relation
• Large-scale inhomogeneities may improve the cosmic concordance of supernovae
• Clustering, Angular Size and Dark Energy
• Constraining the dark energy and smoothness-parameter with supernovae
• Constraining the dark energy and smoothness parameter with type Ia Supernovae and Gamma-Ray Bursts
• Influence of Small-Scale Inhomogeneities on the Cosmological Consistency Tests

Cited by in corpus (4)

• Unbiased constraints on the clumpiness of universe from standard candles
• The $m$-$z$ relation for type Ia supernovae, locally inhomogeneous cosmological models, and the nature of dark matter
• The $m$-$z$ relation for Type Ia supernovae: safety in numbers or safely without worry?
• Impact of small scale inhomogeneities on observations of standard candles