Measuring Global Monopole Velocities, one by one
  We present an estimation of the average velocity of a network of global
monopoles in a cosmological setting using large numerical simulations. In order
to obtain the value of the velocity, we improve some already known methods, and
present a new one. This new method estimates individual global monopole
velocities in a network, by means of detecting each monopole position in the
lattice and following the path described by each one of them. Using our new
estimate we can settle an open question previously posed in the literature:
velocity-dependent one-scale (VOS) models for global monopoles predict two
branches of scaling solutions, one with monopoles moving at subluminal speeds
and one with monopoles moving at luminal speeds. Previous attempts to estimate
monopole velocities had large uncertainties and were not able to settle that
question. Our simulations find no evidence of a luminal branch. We also
estimate the values of the parameters of the VOS model. With our new method we
can also study the microphysics of the complicated dynamics of individual
monopoles. Finally we use our large simulation volume to compare the results
from the different estimator methods, as well as to asses the validity of the
numerical approximations made.
