PBH and DM from cosmic necklaces

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.