Black Holes as Beads on Cosmic Strings
  We consider the possibility of formation of cosmic strings with black holes
as beads. We focus on the simplest setup where two black holes are formed on a
long cosmic string. It turns out the in absence of a background magnetic field
and for observationally viable values for cosmic string tensions, $\mu<2\times
10^{-7}$, the tension of the strut in between the black holes has to be less
than the ones that run into infinity. This result does not change if a
cosmological constant is present. However if the background magnetic field is
turned on, we can have stable setups where the tensions of all cosmic strings
are equal. We derive the equilibrium conditions in each of these setups
depending on whether the black holes are extremal or non-extremal. We obtain
cosmologically acceptable solutions with solar mass black holes and
intragalactic strength cosmic magnatic field.
