HIGH ENERGY THEORY / RELATIVITY / COSMOLOGY SEMINARS
Fall 2006
Friday September 15 Seminar :
Amir Hajian (Princeton University)
Title : Statistical Isotropy of the WMAP Data: Myths and facts about a preferred axis in the Universe
Abstract:
| Simplest models of the Universe
predict no preferred direction on large scales of the
observable Universe. CMB anisotropy is a strong probe of
the Universe on its largest scales. Statistical
properties of a CMB anisotropy map are usually assumed to
be invariant under the rotations of the sky. This
assumption simplifies many problems in CMB and allows us
to use the well known angular power spectrum for model
comparisons with no loss in the information. However
there are certain cases (e.g., multiply-connected cosmic
topology, anisotropic cosmological models (such as
Bianchi models), or observational artifacts like
non-circular beam or residuals from foregrounds) which
break down the above symmetries. We use the Bipolar Power
Spectrum (BiPS) to investigate the rotational symmetries
(statistical isotropy) of CMB anisotropy maps measured by
the Wilkinson Microwave Anisotropy Probe (WMAP) as
distinct from Gaussianity. We show how this can be used
to test the global isotropy of the Universe and to
constrain scenarios that could give rise to a preferred
direction. |
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