Description |
The standard model of cosmology predicts a statistically isotropic distribution of fluctuations in the measured Cosmic
Microwave Background (CMB) temperature and polarisation maps. Enigmatic anomalies claimed in the WMAP and
Planck CMB sky maps could challenge the standard model. However, these claims need to be cast in an objective
mathematical framework and established with statistical rigour. We present a general method for Bayesian inference
of the underlying covariance structure of random fields on a sphere. We employ the Bipolar Spherical Harmonic (BipoSH)
representation of general covariance structure on the sphere. We illustrate the efficacy of the method with a principled
approach to assess violation of statistical isotropy (SI) in the sky maps of CMB fluctuations. We pay particular attention
to quantifying the significance of the tentative evidence for a Cosmic Hemispherical asymmetry.
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