  Cosmic strings with degrees of freedom beyond the standard
Abrikosov-Nielsen-Olesen or Nambu-Goto strings are ubiquitous in field theory
as well as in models with extra dimensions, such as string theoretic brane
inflation scenarios. Here we carry out an analytic study of a simplified
version of one such cosmic string model. Specifically, we extend the
velocity-dependent one-scale (VOS) string evolution model to the case where
there is a conserved microscopic charge on the string worldsheet. We find that
whether the standard scale-invariant evolution of the network is preserved or
destroyed due to the presence of the charge will crucially depend on the amount
of damping and energy losses experienced by the network. This suggests, among
other things, that results derived in Minkowski space (field theory)
simulations may not extend to the case of an expanding universe.
