Topological Spin-Statistics Theorem for Strings
  Recently, a topological proof of the spin-statistics Theorem has been proposed for a system of point particles which does not require relativity or field theory, but assumes the existence of antiparticles. We extend this proof to a system of string loops in three space dimensions and show that by assuming the existence of antistring loops, one can prove a spin-statistics theorem for these string loops. According to this theorem, all unparametrized strings(such as flux tubes in superconductors and cosmic strings ) should be quantized as bosons. Also, as in the point particle case, we find that the theorem excludes nonabelian statistics. 
A.P.Balachandran, W.D.McGlinn, L.O'Raifeartaigh, S.Sen, R.D.Sorkin,   A.M.Srivastava