Revisiting the VOS model for monopoles
  We revisit the physical properties of global and local monopoles and discuss
their implications in the dynamics of monopole networks. In particular, we
review the Velocity-dependent One-Scale (VOS) model for global and local
monopoles and propose physically motivated changes to its equations. We suggest
a new form for the acceleration term of the evolution equation of the
root-mean-squared velocity and show that, with this change, the VOS model is
able to describe the results of radiation and matter era numerical simulations
of global monopole networks with a single value of the acceleration parameter
$k$, thus resolving the tension previously found in the literature. We also
show that the fact that the energy of global monopoles is not localized within
their cores affects their dynamics and, thus, the Hubble damping terms in the
VOS equations. We study the ultra-relativistic linear scaling regime predicted
by the VOS equations and demonstrate that it cannot be attained either on
radiation or matter eras and, thus, cannot arise from the cosmological
evolution of a global monopole network. We also briefly discuss the
implications of our findings for the VOS model for local monopoles.
