The evolution of a globular cluster is dominated by the gravitational interaction between the component
stars in the cluster. The overall structure of the cluster as well as the dynamics of most of the stars in the
cluster are determined by simple -body gravitational dynamics. However, the evolutionary
time scales of stellar evolution are comparable to the relaxation time and core collapse time of
the cluster. Consequently, stellar evolution affects the masses of the component stars of the
cluster, which affects the dynamical state of the cluster. Thus, the dynamical evolution of the
cluster is coupled to the evolutionary state of the stars. Also, as we have seen in the previous
section, stellar evolution governs the state of the binary evolution and binaries may provide a
means of support against core collapse. Thus, the details of binary evolution as coupled with
stellar evolution must also be incorporated into any realistic model of the dynamical evolution of
globular clusters. To close the loop, the dynamical evolution of the globular cluster affects the
distribution and population of the binary systems in the cluster. In our case, we are interested
in the end products of binary evolution, which are tied both to stellar evolution and to the
dynamical evolution of the globular cluster. To synthesize the population of relativistic binaries, we
need to look at the dynamical evolution of the globular cluster as well as the evolution of the
binaries in the cluster. MODEST (MOdeling DEnse STellar systems), a collaboration of various
groups working stellar dynamics, maintains a website that provides the latest information about
efforts to combine simulations of both the dynamical evolution of
-body systems and stellar
evolution [151
].
General approaches to this problem involve solving the -body problem for the component stars in
the cluster and introducing binary and stellar evolution when appropriate to modify the
-body
evolution. There are two fundamental approaches to tackling this problem - direct integration of the
equations of motion for all
bodies in the system and large-
techniques, such as Fokker-Planck
approximations coupled with Monte Carlo treatments of binaries (see Heggie et al. [99] for a
comparison of these techniques). For a recent review of progress in implementing these techniques,
see the summary of the MODEST-2 meeting [218]. In the next two Sections 5.1 and 5.2, we
discuss the basics of each approach and their successes and shortfalls. We conclude in Section 5.3
with a discussion of the recent relativistic binary population syntheses generated by dynamical
simulations.
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