Cosmology of Scalar Field Dark Matter with Self-Interactions

Abstract

In the standard model of the universe, the presence of a cold and dark form of matter is essential for explaining a wide range of observables, from the very largest scales such as the microwave background radiation, to galaxies and sub-galactic scales. However, despite this dark matter being about five times more abundant than all of the visible matter in our universe, its true identity is a complete mystery. Unveiling the fundamental nature of dark matter would contribute to a deeper understanding of our universe and the physical laws that govern it, and is therefore one of the Holy Grails of modern physics. In this thesis I have explored how dark matter behaves (in sometimes surprising ways) in models where the hypothetical dark matter particle is very light and self-interacting, using both theoretical tools and numerical simulations. This effort has contributed to an improved understanding of these models in certain scenarios, as well as provided additional constraints on the free parameters of these models by investigating their effect on observables.