Galactic Cosmic Strings as Sources of Primary Antiprotons
  A possible signature of a class of superconducting cosmic strings trapped in the Milky Way plasma is the emission of low energy antiprotons due to baryon number violating processes on the string. We find the terrestrial flux and the energy spectrum of such antiprotons. Current observational bounds on the flux of low energy antiprotons place a {\it lower} bound on the string tension which is comparable to that given by the electroweak scale. 
Glenn D. Starkman and Tanmay Vachaspati