The Kinematic Richness of Star Clusters I. Isolated Spherical Models
  with Primordial Anisotropy
  We investigate the dynamical evolution of isolated equal-mass star cluster
models by means of direct N-body simulations, primarily focusing on the effects
of the presence of primordial anisotropy in the velocity space. We found
evidence of the existence of a monotonic relationship between the moment of
core collapse and the amount and flavour of anisotropy in the stellar system.
Specifically, equilibria characterised by the same initial structural
properties (Plummer density profile) and with different degrees of
tangentially-biased (radially-biased) anisotropy, reach core collapse earlier
(later) than isotropic models. We interpret this result in light of an
accelerated (delayed) phase of the early evolution of collisional stellar
systems "anisotropic-response"), which we have characterised both in terms of
the evolution of the velocity moments and of a fluid model of two-body
relaxation. For the case of the most tangentially anisotropic model the initial
phase of evolution involves a catastrophic collapse of the inner part of the
system which continues until an isotropic velocity distribution is reached.
This study represents a first step towards a comprehensive investigation of the
role played by kinematic richness in the long-term dynamical evolution of
collisional systems.
