  Nuclear star clusters (NSCs) are dense stellar clusters observed in galactic
nuclei, typically hosting a central massive black hole. Here we study the
possible formation and evolution of NSCs through the inspiral of multiple star
clusters hosting intermediate mass black holes (IMBHs). Using an N-body code we
examine the dynamics of the IMBHs and their effects on the NSC. We find that
IMBHs inspiral to the core of the newly formed NSC and segregate there.
Although the IMBHs scatter each other and the stars, none of them is ejected
from the NSC. The IMBHs are excited to high eccentricities and their radial
density profile develops a steep power-law cusp. The stars also develop a
power-law cusp (instead of the central core that forms in their absence), but
with a shallower slope. The relaxation rate of the NSC is accelerated due to
the presence of IMBHs, which act as massive-perturbers. This in turn fills the
loss-cone and boosts the tidal disruption rate of stars both by the MBH and the
IMBHs to a value excluded by rate estimates based on current observations. Rate
estimates of tidal disruptions can therefore provide a cumulative constraint on
the existence of IMBHs in NSCs.
