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Delensing the CMB to refine estimates of CIPs and fine-structure constant pertubations

Presentation #214.07 in the session “CMB”.

Published onJan 11, 2021
Delensing the CMB to refine estimates of CIPs and fine-structure constant pertubations

The cosmic microwave background (CMB) is made of photons which scattered when the universe expanded enough to become transparent for the first time, also known as recombination. The power spectra of perturbations in the temperature and polarization patterns are responsible for the many breakthroughs that have come from CMB cosmology. As the CMB propagates towards observers, it is deflected by matter along the line of sight. Compensated isocurvature perturbations (CIPs) and spatial variations in the fine structure constant (alpha fluctuations) would have a similar effect on the power spectrum relative to that of a universe in which they do not exist. Proposed by certain inflationary theories, CIPs are fluctuations in both types of matter (dark and baryonic) that are equal and opposite, resulting in the overall density, and thus curvature, of space to be constant. The conditions that cause recombination depend on alpha, meaning that spatial variation of this quantity makes the surface of last scattering wrinkly which obscures the power spectra. The magnitude of lensing is undisputed, and much greater than the proposed magnitude of these other effects. Using the observed CMB it is difficult to discern how much of the smoothing is caused by gravitational lensing, and how much could be caused by these other effects. Internal estimates of the lensing potential will be used to delense the CMB and create a refined estimate of CIPs and alpha fluctuations based on the unlensed power spectra.

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