Expected dipole asymmetry in CMB polarization

TL;DR

This paper investigates the expected hemispherical asymmetry in CMB polarization, analyzing how different primordial perturbations can produce observable asymmetries in polarization correlations, potentially distinguishing their origins.

Contribution

It provides a theoretical analysis of polarization asymmetries in CMB due to various primordial perturbations, highlighting cases where polarization asymmetries surpass temperature anisotropy asymmetries.

Findings

Polarization asymmetry can be larger than temperature asymmetry in certain scenarios.

Different primordial modes produce distinct polarization asymmetry patterns.

Angular scale dependence helps identify the origin of asymmetry.

Abstract

We explore the hemispherical asymmetry predicted in cosmic microwave background polarization when there is an asymmetry in temperature anisotropies due to primordial perturbations. We consider the cases of asymmetries due to adiabatic and isocurvature modes, and tensor perturbations. We show that the asymmetry in the TE, EE and/or BB correlations can be substantially larger than those in the TT power spectrum in certain cases. The relative asymmetry in the different cross-correlations, as well as the angular scale dependence, can in principle distinguish between different origins for the asymmetry.