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Testing isotropy of cosmic microwave background radiation

Kumar Samal, Pramoda
Saha, Rajib
Jain, Pankaj
Ralston, John P.
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Abstract
We introduce new symmetry-based methods to test for isotropy in cosmic microwave background (CMB) radiation. Each angular multipole is factored into unique products of power eigenvectors, related multipoles and singular values that provide two new rotationally invariant measures mode by mode. The power entropy and directional entropy are new tests of randomness that are independent of the usual CMB power. Simulated Galactic plane contamination is readily identified. The ILC–WMAP data maps show seven axes well aligned with one another and the direction Virgo. Parameter free statistics find 12 independent cases of extraordinary axial alignment, low power entropy, or both having 5 per cent probability or lower in an isotropic distribution. Isotropy of the ILC maps is ruled out to confidence levels of better than 99.9 per cent, whether or not coincidences with other puzzles coming from the Virgo axis are included. Our work shows that anisotropy is not confined to the low l region, but extends over a much larger l range.
Description
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2008 The Authors. Journal compilation © 2008 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date
2008-03-13
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Oxford University Press
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Keywords
Methods: data analysis, Methods: statistical, Cosmic microwave background
Citation
Pramoda Kumar Samal, Rajib Saha, Pankaj Jain, John P. Ralston, Testing isotropy of cosmic microwave background radiation, Monthly Notices of the Royal Astronomical Society, Volume 385, Issue 4, April 2008, Pages 1718–1728, https://doi.org/10.1111/j.1365-2966.2008.12960.x
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