MG12 - Talk detail |
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Participant |
Wiltshire, David | |
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Institution |
University of Canterbury - Dept of Physics & Astronomy, Private Bag 4800 - Christchurch - - New Zealand | |
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Session |
Talk |
Abstract |
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PS |
Dark energy from cosmic structure |
Below scales of about 100/h Mpc our universe displays a complex inhomogeneous structure dominated by voids, with clusters of galaxies in sheets and filaments. The coincidence that cosmic expansion appears to start accelerating at the epoch when such structures form has prompted a number of researchers to question whether dark energy is a signature of a failure of the standard cosmology to properly account, on average, for the distribution of matter we observe. Several ideas have been put forward, with intense debate and controversy. I will discuss the debate and the key issues which involve both the change to average cosmic evolution from backreaction, and the solution to the "fitting problem": How do our own observations relate to average quantities when the variance of local geometry becomes significant? I will suggest that a viable alternative to a smooth dark energy may exist purely in general relativity, and will discuss the observational signatures which will allow such a scenario to be tested in future and distinguished from a homogeneous isotropic cosmology with smooth dark energy. |