Majorana zero modes
  We derive the zero mode solutions for a Majorana fermion in the background of a cosmic string and contrast it with the zero mode solution for a (neutral) Dirac fermion. A Majorana zero mode carries no vector or axial charge, and it cannot be bosonised. We study the implications for vorton formation and stability. In the massless limit stability of the zero mode is guaranteed by energy-momentum conservation. However, zero modes obtain an effective mass on string loops. It is found that the conditions under which current formation can be effective are exactly those for which zero mode decay is most likely to occur. 
Rachel Jeannerot and Marieke Postma