Next Contents Previous  3.4. Macroscopic string description  Let
us recapitulate briefly the microphysics setting before we see
its connection with the macroscopic string description we will
develop below. We consider a Witten-type bosonic
superconductivity model in which the fundamental Lagrangian is
invariant under the action of a U(1) × U(1) symmetry group. The
first U(1) is spontaneously broken through the usual Higgs
mechanism in which the Higgs field Phi acquires a non-vanishing
vacuum expectation value. Hence, at an energy scale ms ~
lambdaphi1/2 eta (we will call ms = m hereafter) we are left
with a network of ordinary cosmic strings with tension and
energy per unit length T ~ U ~ m2, as dictated by the Kibble
mechanism.  The Higgs field is coupled not only with its
associated gauge vector but also with a second charged scalar
boson sum, the current carrier field, which in turn obeys a
quartic potential. A second phase transition breaks the second
U(1) gauge (or global, in the case of neutral currents