Averaged Lemaître-Tolman-Bondi dynamics

Abstract

We consider cosmological backreaction effects in Buchert's averaging formalism on the basis of an explicit solution of the Lemaître-Tolman-Bondi (LTB) dynamics which is linear in the LTB curvature parameter and has an inhomogeneous bang time. The volume Hubble rate is found in terms of the volume scale factor which represents a derivation of the simplest phenomenological solution of Buchert's equations in which the fractional densities corresponding to average curvature and kinematic backreaction are explicitly determined by the parameters of the underlying LTB solution at the boundary of the averaging volume. This configuration represents an exactly solvable toy model but it does not adequately describe our "real" Universe.

26 pages, 2 figures, comments and references added, to appear in Class. Quantum Grav

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• Replacing dark energy by silent virialisation
• Gauss-Bonnet-Chern approach to the averaged Universe
• The background Friedmannian Hubble constant in relativistic inhomogeneous cosmology and the age of the Universe
• Does spatial flatness forbid the turnaround epoch of collapsing structures?
• Does relativistic cosmology software handle emergent volume evolution?
• The averaging problem on the past null cone in inhomogeneous dust cosmologies