The effect of inhomogeneous expansion on the supernova observations

Abstract

We consider an inhomogeneous but spherically symmetric Lemaitre–Tolman–Bondi modelto demonstrate that spatial variations of the expansion rate can have a significant effect onthe cosmological supernova observations. A model with no dark energy but a local Hubbleparameter about 15% larger than its global value fits the supernova data better than thehomogeneous model with the cosmological constant. The goodness of the fit is not sensitiveto inhomogeneities in the present-day matter density, and our best fit model hasΩM(r) ∼ 0.3, in agreement with galaxy surveys. We also compute the averaged expansion rate, definedby the Buchert equations, of the best fit model and show explicitly that there is no averageacceleration.