A Shock in the Dark: Plasma Instabilities in the Dark Sector 

Long-range interactions in a dark sector can give rise to collective effects reminiscent of those found in Standard Model plasmas. Associated with these collective effects are exponentially-growing instabilities that can significantly alter the large-scale behavior of dark matter, particularly for dark matter structures transiting one another (e.g. the Bullet Cluster). It has been shown in previous work that large swaths of parameter space with couplings orders of magnitude below the naive particle-particle scattering limit may be susceptible to such instabilities; however, in the absence of simulation, the full nonlinear behavior that dominates the late-time dynamics cannot be predicted. In this work, we perform the first dedicated simulations of the nonlinear evolution of dark plasma. The results provide key quantitative insight into the fate of traversing dark matter structures in the presence of a long-range interaction.

Feel free to bring your lunch to enjoy during the seminar!