Dynamical Evolution of Globular Star Clusters, Galactic Nuclei and Clusters of Galaxies, Optical and X-Ray Studies of Binary X-Ray sources, GRAPE-6 N-body Simulations of Globular Star Clusters. Professor Cohn's research centers on the dynamics of stellar systems, including interacting binary stars, star clusters, the Milky Way Galaxy, galactic nuclei, and clusters of galaxies.