Microwave Background Polarization as a Probe of Large-Angle Correlations

Abstract

Two-point correlation functions of cosmic microwave background polarization provide a physically independent probe of the surprising suppression of correlations in the cosmic microwave background temperature anisotropies at large angular scales. We investigate correlation functions constructed from both the Q and U Stokes parameters and from the E and B polarization components. The dominant contribution to these correlation functions comes from local physical effects at the last scattering surface or from the epoch of reionization at high redshift, so all should be suppressed if the temperature suppression is due to an underlying lack of correlations in the cosmological metric perturbations larger than a given scale. We evaluate the correlation functions for the standard $\Lambda$CDM cosmology constrained by the observed temperature correlation function, and compute statistics characterizing their suppression on large angular scales. Future full-sky polarization maps with minimal systematic errors on large angular scales will provide strong tests of whether the observed temperature correlation function is a statistical fluke or reflects a fundamental shortcoming of the standard cosmological model.

10 pages, 7 figures, replaced to match version accepted to PRD

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• Towards testing CMB anomalies using the kinetic and polarized Sunyaev Zel'dovich effects
• Lack-of-correlation anomaly in CMB large scale polarisation maps
• Testing CMB Anomalies in E-mode Polarization with Current and Future Data
• The ISW effect and the lack of large-angle CMB temperature correlations
• Nonlocal Entanglement and Directional Correlations of Primordial Perturbations on the Inflationary Horizon
• Exploring suppressed long-distance correlations as the cause of suppressed large-angle correlations
• Unraveling the CMB lack-of-correlation anomaly with the cosmological gravitational wave background
• CMB two-point angular correlation function in the Ellipsoidal Universe
• New Geometric Representations of the CMB 2pcf
• Testing cosmological models with large-scale power modulation using microwave background polarization observations