Rapid dynamical mass segregation and properties of fractal star clusters
  We investigate the evolution of young star clusters using N-body simulations.
We confirm that subvirial and fractal-structured clusters will dynamically mass
segregate on a short timescale (within 0.5 Myr). We adopt a modified
minimum-spanning-tree (MST) method to measure the degree of mass segregation,
demonstrating that the stars escaping from a cluster's potential are important
for the temporal dependence of mass segregation in the cluster. The form of the
initial velocity distribution will also affect the degree of mass segregation.
If it depends on radius, the outer parts of the cluster would expand without
undergoing collapse. In velocity space, we find 'inverse mass segregation,'
which indicates that massive stars have higher velocity dispersions than their
lower-mass counterparts.
