Viscosity caused by self-gravity in the field of a massive body

This study investigates self-gravity-induced viscosity in collisionless systems in the presence of a massive central body. Employing a kinetic framework based on the Vlasov-Poisson equations, we derive an analytical expression for viscosity arising from self-gravitational interactions. It is found that a self-gravitating medium in an external gravitational field exhibits non-Newtonian fluid behavior with anisotropic properties. The analysis emphasizes how self-gravity modifies hydrodynamic processes, particularly in driving the loss of angular momentum. These findings advance our understanding of collective gravitational effects in collisionless environments, offering potential implications for modeling dark matter dynamics, galactic structure formation, and the evolution of self-gravitating accretion flows.