Instabilities and modes of collisionless stellar disks

C. Hunter

Kalnajs' matrix method for calculating the normal modes of oscillation and instabilities of collisionless stellar disks has been used very sparingly since its publication 25 years ago. The fullest applications have been to singular scalefree disks for which the dynamics simplifies. This paper discusses some of the difficulties of implementing the method, and describes some ways of overcoming them. It also discusses circumstances in which true modes of oscillation, free from Landau damping, can exist.