Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hemispherical power asymmetry in the three-year Wilkinson Microwave
  Anisotropy Probe sky maps   We consider the issue of hemispherical power asymmetry in the three-year WMAP
data, adopting a previously introduced modulation framework. Computing both
frequentist probabilities and Bayesian evidences, we find that the model
consisiting of an isotropic CMB sky modulated by a dipole field, gives a
substantially better fit to the observations than the purely isotropic model,
even when accounting for the larger prior volume. For the ILC map, the Bayesian
log-evidence difference is ~1.8 in favour of the modulated model, and the raw
improvement in maximum log-likelihood is 6.1. The best-fit modulation dipole
axis points toward (l,b) = (225 deg,-27 deg), and the modulation amplitude is
0.114, in excellent agreement with the results from the first-year analyses.
The frequentist probability of obtaining such a high modulation amplitude in an
isotropic universe is ~1%. These results are not sensitive to data set or sky
cut. Thus, the statistical evidence for a power asymmetry anomaly is both
substantial and robust, although not decisive, for the currently available
data. Increased sky coverage through better foreground handling and full-sky
and high-sensitivity polarization maps may shed further light on this issue.

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The categories of this paper are: hep-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: physics
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
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The categories of this paper are: stat
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The categories of this paper are: cs
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The categories of this paper are: nlin
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: cond-mat
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The categories of this paper are: econ