Monday, June 17, 2013 - 11:00am
"Linear perturbation theory in LTB models"
Abstract. Observations of the current expansion rate of the universe indicate that it undergoes a phase of accelerated expansion. In the standard Friedmann models that are based on homogeneity and isotropy, an exotic matter component with negative pressure (either a cosmological constant or dynamical dark energy) has to be assumed to account for this. I will present a different model called Lemaitre-Tolman-Bondi (LTB) model in which the homogeneity assumption is dropped leading to a universe that is isotropic around a central point and anisotropic everywhere else. Regarding our current position in the universe to be located near the centre of a spherical underdense region (void), local accelerated expansion can be achieved without an exotic matter component. I will give an overview over the basic properties of such a model and show how linear perturbations can possibly be set up in there.