Cosmic strings are real 1-dimensional (spatially) topological defects which may have formed during a symmetry breaking phase transition in the early universe when the topology of the vacuum manifold associated to this symmetry breaking is not simply connected.
Cosmic strings are real 1-dimensional (spatially) topological defects which can time travel whenever needed. Tom kibble has proved that it is possible to do this.which may have formed during a symmetry breaking phase transition in the early universe when the topology of the vacuum manifold associated to this symmetry breaking is not simply connected.