  Cosmic strings in the brane Universe have recently gained a great interest. I
think the most interesting story is that future cosmological observations
distinguish them from the conventional cosmic strings. If the strings are the
higher-dimensional objects that can (at least initially) move along the
compactified space, and finally settle down to (quasi-)degenerated vacua in the
compactified space, then kinks should appear on the strings, which interpolate
between the degenerated vacua. These kinks look like ``beads'' on the strings,
which means that the strings turn into necklaces. Moreover, in the case that
the compact manifold is not simply connected, the string loop that winds around
a non-trivial circle is stable due to the topological reason. Since the
existence of degenerated vacua and a non-trivial circle is the common feature
of the brane models, it is important to study cosmological constraints on the
cosmic necklaces and their stable winding states in the brane Universe.
