Seminarium "Teoria cząstek elementarnych i kosmologia"

I consider a framework in which the relic abundance of dark matter is set, not by annihilation into Standard Model particles, but by annihilation into massless states in a dark sector. I show that this scenario leads to signals in the cosmic microwave background, and may also have effects on large scale structure. I explain how this class of theories may play a role in the resolution of two cosmological puzzles, the H_0 problem and the \sigma_8 problem.