Contents I. Introduction
Over the past decades cosmological observations have provided us with a clearer picture of our universe [23], [29], [32], [34], [40]. On the one hand these measurements have confirmed the pillars of the Standard Hot Big-Bang scenario [28], on the other hand they showed the existence of a class of phenomena whose study has opened a window on a completely new and unexplored territory in physics. The atoms which makes planets, stars, the diffuse gas between galaxies and ourselves account only for a small fraction of the total content of the universe. Quite astonishingly 95% of the cosmos is in the form of two invisible components: 27% is in Cold Dark Matter (CDM) particles, which are primarily responsible for the formation of the visible structures in the universe [27]; 73% is in a unknown exotic form, dubbed “dark energy” (DE), which is responsible for the present phase of cosmic accelerated expansion [8].
