Implications of dark matter free streaming in the early Universe

In this thesis, we link astrophysics and particle physics aspects in order to study the implications of the nature and properties of different types of dark matter candidates on the observable Universe. The main property which connects the different works on which this manuscript is based is free-streaming.
After giving a general overview of cosmology and dark matter, we present a study on a mixed model, where dark matter consists of a standard cold fraction plus a fraction given by another component non-cold. By varying both the mass and the fraction of the non-cold dark matter candidate in a sufficient range, we obtain bounds on the fraction of the non-cold dark matter component with respect to the total dark matter, as a function of its mass. Then, we present a forecast on the mass of the first and smallest dark matter bound systems within a supersymmetric model realized with 9 independent parameters. We analyse the kinetic decoupling temperature and the resulting protohalo masses, which set the power spectrum cutoff. We study correlations among the temperature of kinetic decoupling and the spin-dependent and the spin-independent cross-sections, and address the implications for indirect detection and dark matter searches at colliders. We find that, depending on the nature of the lightest supersymmetric dark matter particle, the values of annihilation cross sections and protohalo masses can change significantly. We also cover scenarios where neutralinos co-annihilate with other supersymmetric particles, and that could be potentially tested by the Large Hadron Collider.