Dark energy or large scale inhomogeneities?

by Dr Antonio E. Romano (Kyoto University)

Wednesday 1 Sept 2010, 11:00 → 12:00 Europe/Zurich

4/2-011 - TH common room (CERN)

As an alternative to dark energy it has been suggested that we may be at the center of an inhomogeneous isotropic universe described by a Lemaitre-Tolman-Bondi (LTB) solution of Einstein's field equations. In order to test this hypothesis we calculate the general analytical formula to fifth order for the redshift spherical shell mass. Using the same analytical method we write the metric in the light-cone by introducing a gauge invariant quantity G(z) which together with the luminosity distance DL(z) completely determine the light-cone geometry of a LTB model. Finally we combine these results with the luminosity distance formulae and show how $\LambdaCDM$ models cannot be mimicked by smooth large scale inhomogeneities, independently of the value of the cosmological constant. We then show how not smooth matter profile can mimick the cosmological constant for both D_L(z) and mn(z), but the solution is unique, making it quite easy to distinguish between LTB and \Lambda CDM models when and additional observable is considered.