Early Universe evolution in presence of magnetic fields

Abstract

We analyse the evolution of a magnetised Universe in a stage between the leptonic era and the beginning of the radiationdominated epoch using an anisotropic Bianchi I model. In our description the cosmic fluid is made of primordial radiation, neutrinos, magnetic field, non-interacting already decoupled dark matter (WIMPS), baryons, electrons, and positrons. The interaction of the field with the electron-positron gas is taken into account, resulting in anisotropic equations of state for these constituents. Numerical simulations reveal some differences between the behaviour of magnetised Bianchi I Universes and that of first order perturbations on an FLRW background.