Supernova Hubble diagram for off-center observers in a spherically symmetric inhomogeneous universe

Abstract

We have previously shown that spherically symmetric, inhomogeneous universe models can explain both the supernova data and the location of the first peak in the CMB spectrum without resorting to dark energy. In this work, we investigate whether it is possible to get an even better fit to the supernova data by allowing the observer to be positioned away from the origin in the spherically symmetric coordinate system. In such a scenario, the observer sees an anisotropic relation between redshifts and the luminosity distances of supernovae. The level of anisotropy allowed by the data will then constrain how far away from the origin the observer can be located, and possibly even allow for a better fit. Our analysis shows that the fit is indeed improved, but not by a significant amount. Furthermore, it shows that the supernova data do not place a rigorous constraint on how far off-center the observer can be located.

Emergent Scenario and Different Anisotropic Models

“…The exact solution have been obtained by Bonnor (1972Bonnor ( , 1974. This simple inhomogeneous cosmological model agrees with current supernova and some other data (Moffat 2005;Moffat 2006;Alnes 2006;Alnes 2007;. Also very recently Clarkson and Marteens (2010) give a justification for inhomogeneous model from the point of view of perturbation analysis.…”

The effect of inhomogeneous expansion on the supernova observations

“…It was shown in [39] that the supernova data does not impose severe restrictions for the location of an off-center observer, but as argued in [34], perhaps the most relevant constraint comes from the dipole anisotropy of the CMB. Here we give a rough estimate for the off-center distance allowed by the CMB dipole.…”

Generalized Lemaître-Tolman-Bondi model with inhomogeneous isotropic dark energy: Observational constraints

“…By inverting the expression z = z(λ, ξ, r obs ) the affine parameter λ may be replaced by the redshift in t, r and θ. The luminosity distance is now obtained from the geodesics for the case of an off-center observer as [44,45] 43) where ... ≡, ξ, r obs and the partial derivatives with respect to ξ are obtained numerically by evaluating the geodesics at slightly different values of ξ. It is easy to see that for the on-center observer we have ∂r(z,ξ,r obs =0) ∂ξ = 0 and ∂θ(z,ξ,r obs =0) ∂ξ = 1 (since θ = ξ) and therefore we re-obtain the expression of the luminosity distance for the on center observer (2.33).…”