The Effect of Stellar Helium Abundance on Dynamics of Multiple
  Populations in Globular Clusters
  We incorporate a semi-analytic formula for the main sequence lifetime of
helium-rich stars in N-body simulations of multiple population globular
clusters to investigate how the enriched helium stars impact the dynamics of
globular clusters. We show that a globular cluster with a helium-rich
concentrated population will be slightly smaller than a globular cluster with a
normal-helium second generation, with the largest difference seen in the
extended normal-helium population. This effect is shown both for a cluster in
isolation and one in a realistic Milky Way tidal field. We show that this
effect is a result of mass segregation, and the earlier loss of more massive
stars in a helium-rich concentrated population due to their decreased main
sequence lifetime. The two populations will therefore become dynamically mixed
at a slightly earlier time than if they have the same helium abundance.
Furthermore, we find that it is possible for the helium-enriched population to
become more extended than the normal-helium population if it forms with a low
initial concentration or the cluster is able to evolve for a large number of
relaxation times. We conclude that the dynamical effects of helium on stellar
masses are modest, and that the initial concentration of the two populations
and the strength of the Milky Way tidal field are more important in determining
the relative radial distributions of multiple populations.
