Monopoles on strings
  In cosmological scenarios based on grand unification, string theory or
braneworlds, many kinds of topological or non-topological defects, including
monopoles and cosmic strings, are predicted to be formed in the early universe.
Here we review specifically the physics of composite objects involving
monopoles tied to strings. There is a wide variety of these, including for
example "dumbbells" and "necklaces," depending on how many strings attach to
each monopole and on the extent to which the various fluxes are confined to the
strings. We also briefly survey the prospects for observing such structures,
the existing observational limits, and potential evidence for a cosmological
role.
