Evolution of the Binary Fraction in Dense Stellar Systems
  Using our recently improved Monte Carlo evolution code, we study the
evolution of the binary fraction in globular clusters. In agreement with
previous N-body simulations, we find generally that the hard binary fraction in
the core tends to increase with time over a range of initial cluster central
densities for initial binary fractions <~ 90%. The dominant processes driving
the evolution of the core binary fraction are mass segregation of binaries into
the cluster core and preferential destruction of binaries there. On a global
scale, these effects and the preferential tidal stripping of single stars tend
to roughly balance, leading to overall cluster binary fractions that are
roughly constant with time. Our findings suggest that the current hard binary
fraction near the half-mass radius is a good indicator of the hard primordial
binary fraction. However, the relationship between the true binary fraction and
the fraction of main-sequence stars in binaries (which is typically what
observers measure) is non-linear and rather complicated. We also consider the
importance of soft binaries, which not only modify the evolution of the binary
fraction, but can drastically change the evolution of the cluster as a whole.
Finally, we describe in some detail the recent addition of single and binary
stellar evolution to our cluster evolution code.
