Supernovae data and perturbative deviation from homogeneity

Abstract

We show that a spherically symmetric perturbation of a dust dominated Ω = 1 FRW universe in the Newtonian gauge can lead to an apparent acceleration of standard candles and provide a fit to the magnitude-redshift relation inferred from the supernovae data, while the perturbation in the gravitational potential remains small at all scales. We also demonstrate that the supernovae data does not necessarily imply the presence of some additional non-perturbative contribution by showing that any Lemaitre-Tolman-Bondi model fitting the supernovae data (with appropriate initial conditions) will be equivalent to a perturbed FRW spacetime along the past light cone.

Large-scale peculiar motions and cosmic acceleration

“…Whereas the effects of large voids have been generally studied in the context of the Lemaitre-Tolman-Bondi (LTB) solution 8 , our analysis has been performed within a perturbed FRW model. The analogies between the two approaches found here, also seem to support the claim by Enqvist, Mattsson & Rigopoulos (2009): that LTB models fitting the supernovae data (with appropriate initial conditions) are equivalent to perturbed FRW spacetimes along the observer's past light-cone. Although single void models appear unrealistic, given the complexity of the observed structure, the simple analysis and the results presented here suggest that (when more realistic averages are performed) identifying the deceleration parameter measured in the frame of a drifting observer with that of the universe itself could be misleading.…”

Geodesic-light-cone coordinates and the Bianchi I spacetime

“…(3.17), the angular distance in a Bianchi I spacetime is given by 51) as found by Saunders in ref. [44] and recently rederived in refs.…”

Redshift and distance in the inhomogeneous universe

“…This is modelled by a constant parameter α (of value between 0 and 1) that multiplies Ω m . Thus, using (27) and (29) we can reduces eq. (22) to [9,10,72] …”