Confronting Lemaitre-Tolman-Bondi models with Observational Cosmology

TL;DR

This paper tests LTB models with observational data, showing they can fit the data as well as LCDM, suggesting we might live in a large local void instead of a dark energy-dominated universe.

Contribution

It introduces specific LTB models with minimal free functions and demonstrates their compatibility with multiple cosmological observations.

Findings

LTB models fit observational data within 1 sigma

Best-fit LTB models have chi^2 close to LCDM

Living in a large local void cannot be excluded

Abstract

The possibility that we live in a special place in the universe, close to the centre of a large void, seems an appealing alternative to the prevailing interpretation of the acceleration of the universe in terms of a LCDM model with a dominant dark energy component. In this paper we confront the asymptotically flat Lemaitre-Tolman-Bondi (LTB) models with a series of observations, from Type Ia Supernovae to Cosmic Microwave Background and Baryon Acoustic Oscillations data. We propose two concrete LTB models describing a local void in which the only arbitrary functions are the radial dependence of the matter density Omega_M and the Hubble expansion rate H. We find that all observations can be accommodated within 1 sigma, for our models with 4 or 5 independent parameters. The best fit models have a chi^2 very close to that of the LCDM model. We perform a simple Bayesian analysis and show that one cannot exclude the hypothesis that we live within a large local void of an otherwise Einstein-de Sitter model.