The Fate of Cosmic String Zero Modes
  Cosmic strings in realistic particle physics models have fermion zero modes in the string core. Such zero modes change the underlying cosmology; for example, the string can carry a current. We consider the stability of fermion zero modes to interactions with particles in the surrounding plasma. We also consider cosmological constraints on such theories, particulary those with a chiral fermion zero mode, such as arises in a class of supersymmetric models. 
Anne-Christine Davis, Stephen C. Davis and Warren B. Perkins