The CMB's polarization was supposed to retell the temperature's story, and at the largest angles it keeps ad-libbing. The TE cross-correlation and EE auto-spectrum at low multipoles carry independent information about recombination, reionization, and the primordial spectrum, and they have accumulated their own anomaly file: the low-ell EE sector drove the systematic-plagued history of the optical depth measurement (tau falling from WMAP's 0.17 to Planck HFI's 0.054 as instrument systematics were excavated); the TE spectrum shows localized deviations from the ΛCDM prediction in the tens-of-multipoles range, with features near ell of 20 to 30 recurring across analyses at 2-to-3 sigma; and the joint low-ell likelihood remains dominated by data treatments rather than cosmic information, an uncomfortable foundation for parameters as consequential as tau, whose value propagates into sigma_8, neutrino masses, and the reionization narrative.
The structural issue is dependency: the model uses the largest polarized scales as a calibration anchor while the same scales host the temperature anomaly family, and ΛCDM's prediction is rigid, large-angle polarization must be the lensed, reionization-screened processing of the same statistically isotropic field. If the temperature anomalies are physical, deposition-era structure rather than flukes, their polarization companions live exactly where the TE/EE sector misbehaves, entangled with the systematics excavation, and current data cannot separate an instrument's residuals from a universe's fingerprints at these multipoles.
The standing is an unsettled foundation under active excavation: low-ell polarization remains the most systematics-limited regime in CMB science, every anomaly retest and every tau-dependent parameter waits on it, and LiteBIRD was designed essentially for this sector.