Problems of Collisional Stellar Dynamics
  The discovery of dynamical friction was Chandrasekhar's best known
contribution to the theory of stellar dynamics, but his work ranged from the
few-body problem to the limit of large N (in effect, galaxies). Much of this
work was summarised in the text "Principles of Stellar Dynamics" (Chandrasekhar
1942, 1960), which ranges from a precise calculation of the time of relaxation,
through a long analysis of galaxy models, to the behaviour of star clusters in
tidal fields. The later edition also includes the work on dynamical friction
and related issues. In this review we focus on progress in the collisional
aspects of these problems, i.e. those where few-body interactions play a
dominant role, and so we omit further discussion of galaxy dynamics. But we try
to link Chandrasekhar's fundamental discoveries in collisional problems with
the progress that has been made in the 50 years since the publication of the
enlarged edition.
