Constraining dark matter self-interactions with simulations and observations

The standard model of cosmology assumes that dark matter interacts with itself and with other matter and energy via gravity only. This is the simplest possible model for dark matter and it describes a wide range of observations of our Universe quite well. However, recent comparisons to observations on small scales appear at odds with theoretical predictions, which might suggest that dark matter is more complex than previously assumed. From a particle physics point of view, there are strong theoretical reasons for believing that dark matter should weakly interact with itself, but the degree of complexity of these interactions is poorly understood. We will explore the consequences of self-interacting dark matter (SIDM) on a wide range of scales using full cosmological hydrodynamical simulations, going beyond the simplest assumption of elastic scattering. We will make comparisons to a variety of observations to determine with SIDM provides an acceptable solution to the tensions with the standard model.