  We report the combined results of molecular dynamics simulations and
theoretical calculations concerning various dynamical arrest transitions in a
model system representing a dipolar fluid, namely, N (softcore) rigid spheres
interacting through a truncated dipole-dipole potential. By exploring different
regimes of concentration and temperature, we find three distinct scenarios for
the slowing down of the dynamics of the translational and orientational degrees
of freedom: At low ({$\eta$} = 0.2) and intermediate (${\eta}$ = 0.4) volume
fractions, both dynamics are strongly coupled and become simultaneously
arrested upon cooling. At high concentrations ({$\eta$} $\lt$ 0.6), the
translational dynamics shows the features of an ordinary glass transition,
either by compressing or cooling down the system, but with the orientations
remaining ergodic, thus indicating the existence of partially arrested states.
In this density regime, but at lower temperatures, the relaxation of the
orientational dynamics also freezes. The physical scenario provided by the
simulations is discussed and compared against results obtained with the
self-consistent generalized Langevin equation theory, and both provide a
consistent description of the dynamical arrest transitions in the system. Our
results are summarized in an arrested states diagram which qualitatively
organizes the simulation data and provides a generic picture of the glass
transitions of a dipolar fluid.
