Overview
In this talk, I will discuss gravitational collapse in two systems. First, I will present KiSS-SIDM, a novel code for following the gravothermal collapse of self-interacting dark matter halos. By assuming spherical symmetry and adopting a new-to-the-field scattering algorithm, the code dramatically improves on the speed and accuracy of previous N-body methods, enabling exploration of parameter space on a laptop. Further, the code enables simulating deep into the core collapse regime, where we find that non-equilibrium effects alter the evolution compared to the commonly adopted “conducting fluid” model. Second, I will discuss the gravitational collapse of the clouds in which the first generation, Population III stars form. While gravitational instability in present day star forming clouds is understood to be driven by supersonic turbulence, Population III star forming clouds are weakly turbulent and thermal pressure dominated. I discuss the physics of cooling-regulated gravitational instability in this environment, and the implications for the initial mass function of Population III stars.