Gravitational and Particle Radiation from Cosmic Strings
  Gravitational and massless particle radiation of straight cosmic strings with finite thickness is studied analytically. It is found that the non-linear interaction of the radiation fields emitted by a cosmic string with the ones of the string always makes the spacetime singular at the symmetry axis. The singularity is not removable and is a scalar one. 
Anzhong Wang and Nilton O. Santos