SEVEN-YEAR <i>WILKINSON MICROWAVE ANISOTROPY PROBE</i> ( <i>WMAP</i> ) OBSERVATIONS: ARE THERE COSMIC MICROWAVE BACKGROUND ANOMALIES?

Abstract

(Abridged) A simple six-parameter LCDM model provides a successful fit to\nWMAP data, both when the data are analyzed alone and in combination with other\ncosmological data. Even so, it is appropriate to search for any hints of\ndeviations from the now standard model of cosmology, which includes inflation,\ndark energy, dark matter, baryons, and neutrinos. The cosmological community\nhas subjected the WMAP data to extensive and varied analyses. While there is\nwidespread agreement as to the overall success of the six-parameter LCDM model,\nvarious "anomalies" have been reported relative to that model. In this paper we\nexamine potential anomalies and present analyses and assessments of their\nsignificance. In most cases we find that claimed anomalies depend on posterior\nselection of some aspect or subset of the data. Compared with sky simulations\nbased on the best fit model, one can select for low probability features of the\nWMAP data. Low probability features are expected, but it is not usually\nstraightforward to determine whether any particular low probability feature is\nthe result of the a posteriori selection or of non-standard cosmology. We\nexamine in detail the properties of the power spectrum with respect to the LCDM\nmodel. We examine several potential or previously claimed anomalies in the sky\nmaps and power spectra, including cold spots, low quadrupole power,\nquadropole-octupole alignment, hemispherical or dipole power asymmetry, and\nquadrupole power asymmetry. We conclude that there is no compelling evidence\nfor deviations from the LCDM model, which is generally an acceptable\nstatistical fit to WMAP and other cosmological data.\n

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Affiliated Institutions

• Columbia University US
• Adnet Systems (United States) US
• University of Toronto CA
• University of Chicago US
• University of British Columbia CA
• Canadian Institute for Theoretical Astrophysics CA
• Brown University US
• Johns Hopkins University US
• University of Oxford GB
• Goddard Space Flight Center US
• Princeton University US
• The University of Texas at Austin US

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