Averaging Robertson-Walker Cosmologies

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The so-called cosmological backreaction arises when one directly averages the Einstein equations to recover cosmology. While usually applied to avoid employing dark energy models, strictly speaking any cosmological model should be built from such an averaging procedure rather than an assumed background. We apply the Buchert formalism to Einstein-de Sitter, Lambda CDM and quintessence cosmologies, and as a first approach to the full problem, evaluate numerically the discrepancies arising from linear perturbation theory between the averaged behaviour and the assumed behaviour. (References: J. Behrend, IB and G. Robbers, JCAP01(2008)013, aXiv:0710.4964; IB, G. Robbers and J. Behrend, in preperation)