3. Primordial Magnetogenesis in a Bouncing Universe

Download the arXiv version here!

Context: The sources of magnetic fields in large structures are still unknown. In this research paper, my collaborators (Nelson Pinto-Neto, Santiago Perez-Bergliaffa, and Sandro Vitenti) and I investigate magnetogenesis. Our background cosmology involves a pressureless scalar field that we couple minimally with curvature.

Method: Our first task was to determine the correct initial conditions for the electromagnetic field, which we accomplished through an adiabatic vacuum prescription. We formulated the equation of motion in Hamiltonian form, using time-dependent “mass” and “frequency” functions. By analyzing the Hamilton equations iteratively via frequency expansion, we obtained analytical insights into the behaviour of the electromagnetic field from the asymptotic past to the present, given the initial values of the field and its momentum. We confirmed these results numerically using the programming language Python and the NumCosmo library. Additionally, we identified the parameter space in which the magnetic fields generated by our model are consistent with observations on scales \(>1\) Megaparsec.

Results:

• This model has well-defined adiabatic initial conditions.
• Besides the absence of strong coupling, there is also no backreaction from the electric energy density.
• Moreover, our model predicts a magnetic spectral index \(n_b = 6\), in stark contrast with other primordial magnetogenesis scenarios…
• …while generating primordial magnetic fields consistent with observations!