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What can be learned from the lensed cosmic microwave background B-mode polarization power spectrum?

Smith, Sarah and Challinor, Anthony and Rocha, Graça (2006) What can be learned from the lensed cosmic microwave background B-mode polarization power spectrum? Physical Review D, 73 (2). Art. No. 023517. ISSN 2470-0010. doi:10.1103/PhysRevD.73.023517.

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The effect of weak gravitational lensing on the cosmic microwave background (CMB) temperature anisotropies and polarization will provide access to cosmological information that cannot be obtained from the primary anisotropies alone. We compare the information content of the lensed B-mode polarization power spectrum, properly accounting for the non-Gaussian correlations between the power on different scales, with that of the unlensed CMB fields and the lensing potential. The latter represent the products of an (idealized) optimal analysis that exploits the lens-induced non-Gaussianity to reconstruct the fields. Compressing the non-Gaussian lensed CMB into power spectra is wasteful and leaves a tight degeneracy between the equation of state of dark energy and neutrino mass that is much stronger than in the more optimal analysis. Despite this, a power-spectrum analysis will be a useful first step in analyzing future B-mode polarization data. For this reason, we also consider how to extract accurate parameter constraints from the lensed B-mode power spectrum. We show with simulations that for cosmic-variance-limited measurements of the lensed B-mode power, including the non-Gaussian correlations in existing likelihood approximations gives biased parameter results. We develop a more refined likelihood approximation that performs significantly better. This new approximation should also be of more general interest in the wider context of parameter estimation from Gaussian CMB data.

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Rocha, Graça0000-0002-4150-8076
Additional Information:©2006 The American Physical Society (Received 24 November 2005; published 25 January 2006) The authors would like to thank Antony Lewis for many helpful comments throughout the course of this work. SS was supported by PPARC and the Astrophysics Group, Cavendish Laboratory and GR by the Leverhulme Trust for the duration of this work. AC is supported the Royal Society. Some of the results in this paper have been derived using the HEALPix package [43].
Subject Keywords:cosmology; radiofrequency cosmic radiation; gravitational lenses; dark energy; neutrino mass
Issue or Number:2
Record Number:CaltechAUTHORS:SMIprd06b
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5375
Deposited By: Archive Administrator
Deposited On:16 Oct 2006
Last Modified:08 Nov 2021 20:25

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