Pearson's random walk in the space of the CMB phases: evidence for parity asymmetry

TL;DR

This study investigates parity asymmetry in the CMB by analyzing power spectrum multipoles and phase angles, revealing significant odd/even differences and phase separation, especially in galactic coordinates.

Contribution

It introduces a novel analysis of CMB phases using a random walk approach, highlighting parity asymmetry in both power spectrum and phase angles.

Findings

Power excess in odd multipoles indicating parity asymmetry

Significant separation of even and odd mean phase angles

Parity asymmetry more pronounced in galactic coordinates

Abstract

The temperature fluctuations of the Cosmic Microwave Background (CMB) are supposed to be distributed randomly in both magnitude and phase, following to the simplest model of inflation. In this paper, we look at the odd and even multipoles of the spherical harmonic decomposition of the CMB, and the different characteristics of these, giving rise to a parity asymmetry. We compare the even and odd multipoles in the CMB power spectrum, and also the even and odd mean angles. We find for the multipoles of the power spectrum, that there is power excess in odd multipoles, compared to even ones, meaning that we have a parity asymmetry. Further, for the phases, we present a random walk for the mean angles, and find a significant separation for even/odd mean angles, especially so for galactic coordinates. This is further tested and confirmed with a directional parity test, comparing the parity asymmetry in galactic and ecliptic coordinates.