I consider some of the issues we face in trying to understand dark energy. I discuss how the averaging problem confuses our potential understanding of dark energy by considering the backreaction from density perturbations to second-order in the concordance model: this effect leads to at least a 10% change in the observed value of the deceleration parameter, and could be significantly higher. Large Hubble-scale inhomogeneity has not been investigated in much detail, and could conceivably be the cause of apparent cosmic acceleration. I discuss void models which defy the Copernican principle in our Hubble <br /> patch, and describe how we can potentially rule out these models.
Dark energy and inhomogeneity, Chris Clarkson (University of Cape Town)
May. 04 - 20:30 - 2011
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