The major reason for this difference is that the stellar dynamic problems are harder because they arise in a phase space with twice as many dimensions as physical space. I am working to obtain a dynamical understanding of bar-like instabilities and what it takes to overcome them. Dynamics of Bending Waves in Flattened Stellar Systems I am also interested in the dynamics of bending waves in flattened stellar systems. This topic is relevant to the long-standing problem of explaining warps in disk galaxies. It is now well-known that the gaseous HI layers of many disk galaxies display warps.
Warps are much less easily detectable in stellar disks so that their prevalence is uncertain.
The difficulty of detecting warps in stellar disks suggests that they are stable against bending perturbations. If, as is widely believed, dark halos are a major cause of the warping of the gas beyond the optical disk, it seems unlikely that they would also help stabilize the stellar disk. Understanding what it takes to keep a stellar disk stable against bending perturbations is still needed therefore, especially since some Russian work has shown that stellar disks are liable to violent bending instabilities if they become too thin.