Spiral galaxies as gravitational plasmas

This article reviews recent studies of dynamics of disk-shaped galaxies with special emphasis on their spiral structures. In a local version of kinetic stability theory, the very existence and the value of the critical wavelength of the spiral structure arising due to nonresonant Jeans-type instability of gravity perturbations is explained. A formal analogy between the collective oscillations in a rotating self-gravitating disk and the oscillations of a hot nonneutral plasma in a magnetic field is explored.