http://arxiv.org/abs/1403.2034
Recent measurements of the cosmic microwave background (CMB) radiation show an apparent tension with the present value of the Hubble parameter inferred from local observations of supernovae. We examine the possibility that such a discrepancy is the consequence of the presence of a local inhomogeneity, and find that a local overdensity could in fact account for the difference or at least for part of it. While such a small inhomogeneity would not significantly affect the distance to the last scattering, and consequently the value of $H_0$ obtained from CMB observations, it can have an important effect on the local estimation of $H(z)$, since this is sensitive to the derivative of the luminosity distance. The apparent tension can in fact be solved by correctly extrapolating $H_0$ from the low redshift supernovae observations by taking into account the effects of a local inhomogeneity on the distance redshift relation. To fully explain the difference we find that we need to be located in a region about $45%$ denser than where supernovae are located. Smaller inhomogeneities can still introduce important corrections to the apparent value of $H_0^{app}$ obtained from observational data under the assumption of homogeneity, and need to be considered in the high precision cosmology era in which we are entering.
A. Romano and S. Vallejo
Tue, 11 Mar 14
20/66