New Anomalies in Cosmic Microwave Background Anisotropy: Violation of the Isotropic Gaussian Hypothesis in Low-$l$ Modes

TL;DR

This paper identifies significant anomalies in the low-$l$ modes of the Cosmic Microwave Background, including alignments and unusual power distributions, challenging the standard isotropic Gaussian assumption and hinting at new physics.

Contribution

It reports the discovery of alignments and anomalous power in low-$l$ modes of CMB anisotropies, suggesting deviations from the standard cosmological model.

Findings

Alignment of low-$l$ modes within 1/4 of the northern hemisphere

Anomalously high power in specific low-$l$ modes with probabilities around 0.1% to 1%

Robustness of anomalies against foreground contamination and cleaning methods

Abstract

In the standard framework of cosmology, primordial density fluctuations are assumed to have an isotropic Gaussian distribution. We search for deviations from this assumption in the WMAP data for the low $l$ modes of Cosmic Microwave Background Anisotropies (CMBA), by studying the directions of the z-axis that maximize the $l=m$ modes and the resulting amplitudes of these modes. We find a general alignment of the directions for $l=2$ to 10 modes to within 1/4 of the northern hemisphere. This alignment can be regarded as a generalization of the recently discovered alignment of the $l=2$ and 3 modes - the so-called `Axis of Evil'. Furthermore, we find abnormally high (low) powers in the $l=m=6$, 12 - 17 ($l=m=5$) modes; the probabilities for having the anomalous amplitudes of the $l=m=5$, 6, 17 modes are about 0.1%, 1% and 1% respectively according to the Gaussian conjecture. The alignment and anomalous amplitudes for these low $l$ modes are very robust against foreground contamination or different cleaning strategies, suggesting a cosmological origin and possibly supporting a non-standard inflation.