Magnetized CMB observables: a dedicated numerical approach

TL;DR

This paper develops a new numerical method to analyze how large-scale magnetic fields influence CMB anisotropies, focusing on temperature and polarization spectra with magnetic effects included in initial conditions and dynamics.

Contribution

It introduces a consistent numerical approach to evaluate magnetized CMB anisotropies considering scalar modes and stochastic magnetic fields simultaneously.

Findings

Magnetic fields cause observable distortions in the first seven TT peaks.

Magnetic effects influence the polarization TE spectra at specific peaks.

Degeneracies between magnetic field parameters and cosmological parameters are identified.

Abstract

Large-scale magnetic fields affect the scalar modes of the geometry whose ultimate effect is to determine the anisotropies of the Cosmic Microwave Background (CMB in what follows). For the first time, a consistent numerical approach to the magnetized CMB anisotropies is pursued with the aim of assessing the angular power spectra of temperature and polarization when the scalar modes of the geometry and a stochastic background of inhomogeneous magnetic fields are simultaneously present in the plasma. The effects related to the magnetized nature of the plasma are taken into account both at the level of the dynamical equations and at the level of the initial conditions of the Einstein-Boltzmann hierarchy. The temperature and polarization observables are exploited to infer the peculiar signatures of a pre-equality magnetic field. Using the extrapolated best fit to the three year WMAP data the increase and distortions of the first seven peaks in the TT autocorrelations are monitored for different values of the regularized magnetic field intensity and for the physical range of spectral indices. Similar analyses are also conducted for the first few anticorrelation (and corrrelation) peaks of the TE power spectra. Possible interesting degeneracies and stimulating perspectives are pointed out and explored.