The Disruption of Globular Star Clusters in the Galaxy: A Comparative Analysisbetween Fokker-Planck and [ITAL]N[/ITAL]-Body Models

Recent N-body simulations have shown that there is a serious discrepancybetween the results of the N-body simulations and the results of Fokker-Plancksimulations for the evolution of globular and rich open clusters under theinfluence of the galactic tidal field. In some cases, the lifetime obtained byFokker-Planck calculations is more than an order of magnitude smaller thanthose by N-body simulations. In this letter we show that the principal causefor this discrepancy is an over-simplified treatment of the tidal field used inprevious Fokker-Planck simulations. We performed new Fokker-Planck calculationsusing a more appropriate implementation of the boundary condition of the tidalfield. The implementation is only possible with anisotropic Fokker-Planckmodels, while all previous Fokker-Planck calculations rely on the assumption ofisotropy. Our new Fokker-Planck results agree well with N-body results.Comparison of the two types of simulations gives a better understanding of thecluster evolution.Comment: 10 pages including 4 figures, Latex; ApJ Letters in pres