ABSTRACT
Much of the authors' effort in understanding the long-term evolution and morphology of galaxies has focused on the equilibria of luminous disks and ellipticals. In this chapter, the authors emphasise N-body simulation methods which minimise sampling noise. They describe how the so-called expansion or self-consistent field method can be generalised to treat a wide range of galactic systems with one or more components. The authors mention the excitation of structure by a passing galaxy such as a weak encounter in group, a fly-by. These interactions can cause off-centred disks and centres and trigger bars. Similarly, an orbiting satellite will have a very similar effect on its primary. The authors also describe noise-driven evolution, both the shape and magnitude of fluctuation-driven structure and the possibility of significant evolution of halo profiles due to these fluctuations. They further describe the modal spectra of stellar systems.
