Averaging anisotropic cosmologies

Abstract

We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of anisotropic pressure-free models. Adopting the Buchert scheme, we recast the averaged scalar equations in Bianchi-type form and close the standard system by introducing a propagation formula for the average shear magnitude. We then investigate the evolution of anisotropic average vacuum models and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. The presence of nonzero average shear in our equations also allows us to examine the constraints that a phase of backreaction-driven accelerated expansion might put on the anisotropy of the averaged domain. We close by assessing the status of these and other attempts to define and calculate `average' spacetime behaviour in general relativity.

revised version, to appear in CQG

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Cited by in corpus (11)

• Dark Energy from structure: a status report
• Relativistic Fluid Dynamics: Physics for Many Different Scales
• Relativistic cosmology and large-scale structure
• Relativistic fluid dynamics: physics for many different scales
• The Spatial Averaging Limit of Covariant Macroscopic Gravity - Scalar Corrections to the Cosmological Equations
• Linear and non-Linear Instabilities in Unified Dark Energy Models
• Late time anisotropy as an imprint of cosmological backreaction
• The Averaging Problem in Cosmology
• Multi-fluid cosmology: An illustration of fundamental principles
• Modelling the emergence of cosmic anisotropy from non-linear structures
• Averaging procedure in variable-G cosmologies