Quadrupole--octopole alignment of CMB related to primordial power spectrum with dipolar modulation in anisotropic spacetime

TL;DR

This paper explains the observed alignment of the quadrupole and octopole in the CMB as a natural outcome of an anisotropic primordial power spectrum with dipolar modulation, leading to deviations from isotropy at low multipoles.

Contribution

It introduces a model with an anisotropic primordial power spectrum that accounts for the quadrupole-octopole alignment observed in CMB data.

Findings

Alignment probability is higher than in isotropic models.

The model predicts deviations from statistical isotropy at low multipoles.

The privileged plane maximizes quadrupole-octopole correlation.

Abstract

The WMAP and Planck observations show that the quadrupole and octopole orientations of the CMB might align with each other. We reveal that the quadrupole--octopole alignment is a natural implication of the primordial power spectrum in an anisotropic spacetime. The primordial power spectrum is presented with a dipolar modulation. We obtain the privileged plane by employing the ``power tensor'' technique. At this plane, there is the maximum correlation between quadrupole and octopole. The probability for the alignment is much larger than what in the isotropic universe. We find that this model would lead to deviations from the statistical isotropy only for low--\(\ell\) multipoles.