Promotor: A. Achúcarro, Co-promotor: A. Boyarsky

In the early universe, the dynamics of the Higgs field can give rise to many interesting phenomena.

This thesis explores the theoretical and observational properties of distant massive galaxies that harbour active black holes in their centres and shine brightly at radio wavelengths.

One of the most important correlation functions in physics, especially in cosmology, is the energy density, which describes how much energy is present at each point in spacetime due to matter fields. A key contribution to the energy density of the primordial universe comes from gravitational waves (GWs),…