The galactic stellar nucleation by globular cluster interactions in   dwarf galaxies
  Dinamical Friction Problem is a long-standing dilemma about globular clusters(hereafter,GCs) belonging to dwarf galaxies. The GCs are strongly affected by dynamical friction in dwarf galaxies, and presumed to fall into the galactic center. But GCs do exist in dwarf galaxies. Recentry, a new solution was proposed. If dwarf galaxies have a cored dark matter halo, in which case the effect of dynamical friction will be weaken considerably, and GCs are able to survive beyond the age of the universe. In this study, we discussed why does a constant density cored halo cease dynamical friction, by means of N-body simulations. 
Shigeki M. Inoue, Masafumi Noguchi