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NAM2012 - All Presentation Details

Record 73 of 756

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Decisive tests of large-scale homogeneity

Author: Phil Bull

University of Oxford

Co-Authors:

Session: COS4: Modelling Dark Energy and Modified Gravity

Presentation type: Talk      15:15  Thursday 29th 15:00-17:00 

Summary:

When interpreted within the framework of a spatially homogeneous and isotropic FLRW model, observations of distant supernovae imply the existence of an exotic dark energy component of the cosmological fluid. While CMB observations suggest that the Universe is approximately isotropic about us, much more information is required to establish homogeneity on large scales. Indeed, radially-inhomogeneous "giant void" models can be constructed which precisely reproduce the observed supernova Hubble diagram without requiring dark energy, while still remaining isotropic around observers at the centre of symmetry. A powerful test of inhomogeneity comes from the kinematic Sunyaev-Zel'dovich (kSZ) effect, which effectively allows us to probe conditions inside our past light cone. We use observations of the kSZ effect, plus three other observables, to rule out the general class of spherically-symmetric, inhomogeneous, dust-only models as explanations of the apparent cosmological acceleration. We go on to generalise the kSZ effect to include all CMB blackbody spectral distortions, and use this to propose a general test of homogeneity. This has the capacity to decisively establish the validity of the FLRW metric as a description of the universe on large scales, and in a much more economical way than competing methods.

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