CMB internal delensing with general optimal estimator for higher-order correlations

Toshiya Namikawa
Phys. Rev. D 95, 103514 – Published 24 May 2017

Abstract

We present a new method for delensing B modes of the cosmic microwave background (CMB) using a lensing potential reconstructed from the same realization of the CMB polarization (CMB internal delensing). The B-mode delensing is required to improve sensitivity to primary B modes generated by, e.g., the inflationary gravitational waves, axionlike particles, modified gravity, primordial magnetic fields, and topological defects such as cosmic strings. However, the CMB internal delensing suffers from substantial biases due to correlations between observed CMB maps to be delensed and that used for reconstructing a lensing potential. Since the bias depends on realizations, we construct a realization-dependent (RD) estimator for correcting these biases by deriving a general optimal estimator for higher-order correlations. The RD method is less sensitive to simulation uncertainties. Compared to the previous -splitting method, we find that the RD method corrects the biases without substantial degradation of the delensing efficiency.

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  • Received 20 March 2017

DOI:https://doi.org/10.1103/PhysRevD.95.103514

© 2017 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Toshiya Namikawa

  • Department of Physics, Stanford University, Stanford, California 94305, USA
  • Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA

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Issue

Vol. 95, Iss. 10 — 15 May 2017

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