Abstract
This lecture shows how cosmological simulations can teach us a great deal about the properties of dark matter. Simulation methods are described, first for the gravitational N-body problem, then when gas hydrodynamics are added, and the complexity of associated baryonic phenomena: heating and cooling, dissipation, star formation from dense molecular gas, feedback from supernova explosions, or black hole formation in galaxy nuclei, and feedback from active nuclei, which can stop star formation, etc. The description of large simulations, covering a large fraction of the volume of the universe, containing tens of billions of particles, shows us the predictions of the model: the dark matter profiles in structures, whatever their size or mass, are universal, and resemble a power law in 1/R towards the center. This peculiar distribution is one of the problems of the Standard Model, in its confrontation with observations, since this kind of cusp is not observed but rather density plateaus or cores. What's more, every giant galaxy halo, such as the Milky Way, probably harbours thousands of satellites, which are not observed, and which may be made entirely of dark matter.
