The weird side of the Universe: Preferred axis

TL;DR

This paper investigates large-scale anomalies in the CMB, revealing a stable preferred axis that aligns with other cosmic features, suggesting a possible non-cosmological origin of these anomalies.

Contribution

It demonstrates the directional dependence of CMB parity asymmetry and its stable preferred axis across different analyses and maps.

Findings

CMB parity asymmetry is directionally dependent.

The preferred axis is stable across various analyses.

The preferred axis aligns with the CMB quadrupole, octopole, and kinematic dipole.

Abstract

In both WMAP and Planck observations on the temperature anisotropy of cosmic microwave background (CMB) radiation a number of large-scale anomalies were discovered in the past years, including the CMB parity asymmetry in the low multipoles. By defining a directional statistics, we find that the CMB parity asymmetry is directional dependent, and the preferred axis is stable, which means that it is independent of the chosen CMB map, the definition of the statistic, or the CMB masks. Meanwhile, we find that this preferred axis strongly aligns with those of the CMB quadrupole, octopole, as well as those of other large-scale observations. In addition, all of them aligns with the CMB kinematic dipole, which hints to the non-cosmological origin of these directional anomalies in cosmological observations.