Abstract
Our understanding of current cosmological observations and the formation of the great structures of the Universe (galaxies and beyond) is based in part, in the standard cosmological model, on the existence of an effective fluid of cold dark matter in which the perturbations imprinted during the very primordial phases of the Universe could grow under the effect of gravity, thus enabling the birth and evolution of galaxies. A fundamental question remains: what is the nature of this fluid, and how was it produced, if indeed it is a new form of matter? Theoretical developments in so-called "beyond the standard model" particle physics suggest plausible scenarios characterized by the existence of new particles stable enough to play the role of dark matter.
In this seminar, we will present the most promising classes of scenarios (WIMPs, axions or light scalars, sterile neutrinos, etc.), and explain how present or future observations or experiments can highlight or exclude them. We will see how these scenarios can, under certain conditions, also account for potential small-scale anomalies affecting cold dark matter in its most refined description. Finally, we'll ask to what extent these new particles could coexist with hypothetical primordial black holes, other potential dark matter candidates.
