  We investigate the time taken for global collapse by a dipolar Bose-Einstein
condensate. Two semi-analytical approaches and exact numerical integration of
the mean-field dynamics are considered. The semi-analytical approaches are
based on a Gaussian ansatz and a Thomas-Fermi solution for the shape of the
condensate. The regimes of validity for these two approaches are determined,
and their predictions for the collapse time revealed and compared with
numerical simulations. The dipolar interactions introduce anisotropy into the
collapse dynamics and predominantly lead to collapse in the plane perpendicular
to the axis of polarization.
