Joint Seminars on Cosmology and Gravitation

Speaker: Antonio Enea Romano (YITP)
Title: Apparent cosmological acceleration, dark energy and inhomogeneities.
Date: Tue, Nov 24, 2009, 16:30 - 17:30
Place: Room 630
Abstract: It well known that inhomogeneous spherically symmetric cosmological models (LTB) can explain the luminosity distance data without invoking dark energy.
In this context we first clarify the relation between apparent cosmological acceleration $a_{\Lambda CDM}$ and spatially averaged acceleration $a_D$ , and show that in general a positive $a_D$ does not correspond to models which are able to fit observational data, giving some examples.
We then present some new analytical results in the low red-shift regime for the luminosity distance $D_L(z)$ and the red-shift spherical shell energy density $mn(z)$, and introduce a general approach to the solution of the inversion problem of mapping a LTB model to observations.