Cosmological Features of Primordial Magnetic Fields

TL;DR

This thesis investigates how primordial magnetic fields influence CMB anisotropies, highlighting the role of helicity, IR cutoffs, and gauge invariance, and constrains magnetogenesis scenarios using CMB data.

Contribution

It introduces a comprehensive analysis of primordial magnetic fields' effects on CMB, emphasizing helicity, IR cutoffs, and the equivalence of perturbation approaches, advancing understanding of magnetogenesis.

Findings

Helicity significantly affects CMB polarization and bispectrum signals.

Non-causal fields from inflation are most constrained by CMB observations.

IR cutoffs in spectra produce distinctive features in magnetic field signatures.

Abstract

The aim of this thesis is to study the effects on the CMB anisotropy due to primordial magnetic fields and to analyze some favorable scenarios of magnetogenesis constrained by those signatures, including limits on the amplitude of the fields from bounds on CMB non-Gaussianity and background models. In fact, we found out that helicity in the fields plays an important role in the analysis PMFs origin, by generating significant features in the cross-correlation polarization pattern and the increasing of the signal in the reduced CMB bispectrum. In the latter case, we reported that non-causal fields (mainly generated during the inflation epoch) are the most favorable models constrained by CMB observations. Moreover, we have studied the presence of an IR cutoff in the spectra and bispectra finding appealing unique features from primordial magnetic fields. Another important result shown in this thesis is the equivalence between different approaches of cosmological perturbation theory in the magnetized context. In fact, assuming a magnetized Universe and building gauge invariant quantities in both approaches: the 1+3covariant and the gauge invariant; we found out that those invariants represent the same physical meaning. Besides, we define gauge invariant related to the electromagnetic potentials which in future works, could help us to study magnetogenesis models on perturbed scenarios.