Probing inflation with CMB polarization : weak lensing effect on the covariance of CMB spectra

Abstract

CMB anisotropies are modified by the weak lensing effect of intervening large scale structures on the photon path from the last scattering surface to the observer. This has to be accounted for when observational data of sensitive experiments are used to constrain cosmological models. A common approximation to analyze the CMB angular power spectra is to include only the Gaussian part of the lensing correction and to ignore the non-gaussian terms in the error covariance matrix of the spectra. In order to investigate the validity of this approximation, we computed these non-Gaussian terms by using a perturbative expansion method. We present a graphical method to write down any N-point correlation functions at any order in lensing. We use a pedagogical approach to demonstrate that neglecting non-gaussian terms is an accurate approximation for all polarizations but B, and it will remain so even for the analysis of very sensitive post-Planck experiments. For the B polarization, non-gaussian contributions up to order 4 must be taken into account.

29 pages, 13 figures, JCAP style. Improved to match published version : annex A expanded, references added, few minor corrections

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Cited by in corpus (4)

• In the Realm of the Hubble tension $-$ a Review of Solutions
• Full covariance of CMB and lensing reconstruction power spectra
• Neutrino mass constraints beyond linear order: cosmology dependence and systematic biases
• Understanding the neutrino mass constraints achievable by combining CMB lensing and spectroscopic galaxy surveys