Time Walk Through the Quantum Cosmic String
  Enforcing the spacetime of supermassive cosmic strings to satisfy the symmetry of a gravitational topological defect, that is a spacetime kink, it is shown that the energy of these strings becomes quantized so that only defects whose internal geometry is that of a hemisphere (critical string) and that of a sphere (extreme string) are allowed. In the latter case, the exterior conical singularity becomes an event-horizon singularity which can be removed by using the Kruskal technique in the kink metric. It is also shown that the geodesically complete metric of the extreme string can accommodate closed timelike curves which are compatible with quantum theory, but cannot be noticed by any observers. The quantum string can also drive an essentially unique process of inflationary expansion in its core, without any fine tuning of the initial conditions. 
Pedro F. Gonzalez-Diaz