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Article overview
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Interpreting supernovae observations in a lumpy universe | Chris Clarkson
; George Ellis
; Andreas Faltenbacher
; Roy Maartens
; Obinna Umeh
; Jean-Philippe Uzan
; | Date: |
12 Sep 2011 | Abstract: | Light from ’point sources’ such as supernovae is observed with a beam width
of order of the sources’ size -- typically less than 1 AU. Such a beam probes
matter and curvature distributions that are very different from coarse-grained
representations in N-body simulations or perturbation theory, which are
smoothed on scales much larger than 1 pc. The beam typically travels through
unclustered dark matter and hydrogen with a mean density much less than the
cosmic mean, and through dark matter mini-halos and hydrogen clouds. Large dark
matter halos are rarely encountered directly and so are mainly experienced
through their Weyl (tidal) curvature. How observations of many such beams
averages this Weyl curvature into the Ricci curvature of the background is not
understood. If modelled incorrectly this can lead to significant changes to the
inferred background cosmology. Standard analyses predict a huge variance for
such tiny beam sizes, and non-linear corrections appear to be non-trivial. By
considering different reasonable approximations which yield very different
cosmologies we argue that modelling ultra-narrow beams accurately is a critical
problem for precision cosmology. | Source: | arXiv, 1109.2484 | Services: | Forum | Review | PDF | Favorites |
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