Effects of helical magnetic fields on the cosmic microwave background

TL;DR

This paper presents a comprehensive numerical analysis of how stochastic helical magnetic fields influence the temperature anisotropies and polarization patterns of the cosmic microwave background, including parity-odd correlations.

Contribution

It provides the first complete numerical calculation of CMB anisotropies considering scalar, vector, and tensor modes with helical magnetic fields, including damping effects.

Findings

Helical magnetic fields induce parity-odd correlations in CMB polarization.

Numerical results include contributions from all mode types and damping effects.

Parity-odd correlations (EB and TB) are significant signatures of magnetic helicity.

Abstract

A complete numerical calculation of the temperature anisotropies and polarization of the cosmic microwave background (CMB) in the presence of a stochastic helical magnetic field is presented which includes the contributions due to scalar, vector and tensor modes. The correlation functions of the magnetic field contributions are calculated numerically including a Gaussian window function to effectively cut off the magnetic field spectrum due to damping. Apart from parity-even correlations the helical nature of the magnetic field induces parity-odd correlations between the E- and B-mode of polarization (EB) as well as between temperature (T) and the polarization B-mode (TB).