NonGaussian structure of Bmode polarization after delensing
The Bmode polarization of the cosmic microwave background on large scales has been considered as a probe of gravitational waves from the cosmic inflation. Ongoing and future experiments will, however, suffer from contamination due to the Bmodes of nonprimordial origins, one of which is the lensing induced Bmode polarization. Subtraction of the lensing Bmodes, usually referred to as delensing, will be required for further improvement of detection sensitivity of the gravitational waves. In such experiments, knowledge of statistical properties of the Bmodes after delensing is indispensable to likelihood analysis particularly because the lensing Bmodes are known to be nonGaussian. In this paper, we study nonGaussian structure of the delensed Bmodes on large scales, comparing it with that of the lensing Bmodes. In particular, we investigate the power spectrum correlation matrix and the probability distribution function (PDF) of the power spectrum amplitude. Assuming an experiment in which the quadratic delensing is an almost optimal method, we find that delensing reduces correlations of the lensing Bmode power spectra between different multipoles, and that the PDF of the power spectrum amplitude is well described as a normal distribution function with a variance larger than that in the case of a Gaussian field. Thesemore »
 Authors:

^{[1]};
^{[2]}
 Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
 High Energy Accelerator Research Organization (KEK), Ibaraki (Japan)
 Publication Date:
 Report Number(s):
 SLACPUB16654
Journal ID: ISSN 14757516; arXiv:1506.09209
 Grant/Contract Number:
 AC0276SF00515
 Type:
 Accepted Manuscript
 Journal Name:
 Journal of Cosmology and Astroparticle Physics
 Additional Journal Information:
 Journal Volume: 2015; Journal Issue: 10; Journal ID: ISSN 14757516
 Publisher:
 Institute of Physics (IOP)
 Research Org:
 SLAC National Accelerator Lab., Menlo Park, CA (United States)
 Sponsoring Org:
 USDOE Office of Science (SC)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTRONOMY AND ASTROPHYSICS; astrophysics; ASTRO; gravitational lensing; CMBR polarisation; gravitational waves and CMBR polarization
 OSTI Identifier:
 1270631
Namikawa, Toshiya, and Nagata, Ryo. NonGaussian structure of Bmode polarization after delensing. United States: N. p.,
Web. doi:10.1088/14757516/2015/10/004.
Namikawa, Toshiya, & Nagata, Ryo. NonGaussian structure of Bmode polarization after delensing. United States. doi:10.1088/14757516/2015/10/004.
Namikawa, Toshiya, and Nagata, Ryo. 2015.
"NonGaussian structure of Bmode polarization after delensing". United States.
doi:10.1088/14757516/2015/10/004. https://www.osti.gov/servlets/purl/1270631.
@article{osti_1270631,
title = {NonGaussian structure of Bmode polarization after delensing},
author = {Namikawa, Toshiya and Nagata, Ryo},
abstractNote = {The Bmode polarization of the cosmic microwave background on large scales has been considered as a probe of gravitational waves from the cosmic inflation. Ongoing and future experiments will, however, suffer from contamination due to the Bmodes of nonprimordial origins, one of which is the lensing induced Bmode polarization. Subtraction of the lensing Bmodes, usually referred to as delensing, will be required for further improvement of detection sensitivity of the gravitational waves. In such experiments, knowledge of statistical properties of the Bmodes after delensing is indispensable to likelihood analysis particularly because the lensing Bmodes are known to be nonGaussian. In this paper, we study nonGaussian structure of the delensed Bmodes on large scales, comparing it with that of the lensing Bmodes. In particular, we investigate the power spectrum correlation matrix and the probability distribution function (PDF) of the power spectrum amplitude. Assuming an experiment in which the quadratic delensing is an almost optimal method, we find that delensing reduces correlations of the lensing Bmode power spectra between different multipoles, and that the PDF of the power spectrum amplitude is well described as a normal distribution function with a variance larger than that in the case of a Gaussian field. These features are well captured by an analytic model based on the 4th order Edgeworth expansion. Furthermore, as a consequence of the nonGaussianity, the constraint on the tensortoscalar ratio after delensing is degraded within approximately a few percent, which depends on the multipole range included in the analysis.},
doi = {10.1088/14757516/2015/10/004},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 10,
volume = 2015,
place = {United States},
year = {2015},
month = {10}
}