CMB low multipole alignments across WMAP and \emph{Planck} data releases

TL;DR

This study analyzes multiple WMAP and Planck data releases to investigate large-scale anomalies in the CMB, finding consistent multipole alignments and deviations from isotropy that challenge the cosmological principle.

Contribution

It provides a comprehensive, multi-release analysis of CMB multipole alignments using invariant statistics, revealing persistent anomalies and new alignments across datasets.

Findings

Consistent multipole alignments across WMAP and Planck data.

Power entropy indicates less randomness than expected at large scales.

Anomalies challenge the assumption of isotropy in the universe.

Abstract

The first observations of the cosmic microwave background (CMB) from NASA's \emph{Wilkinson Microwave Anisotropy Probe} (WMAP) led to finding `alignment' anomalies not expected from fluctuations in the isotropic cosmological model. We study the data of all 8 full-sky public releases since then to test for anomalous alignments and shapes of the first 60 multipoles, i.e., over the range $2\leq l \leq 61$. We use rotationally invariant and covariant statistics to test isotropy of all subsequent WMAP data releases, along with those from the ESA's \emph{Planck} mission. Anomalous alignments among the multipoles $l=1, 2, 3$ are very consistent and robust. More alignments are detected, some of them new, while significance is diluted by the large range of the search. Power entropy, a measure of the randomness of the multipoles, is consistently anomalous at about $2\sigma$ level or better across all data releases. It appears that the CMB is not as random as the cosmological principle predicts on large angular scales