Flux tubes, visons, and vortices in spin-charge separated   superconductors
  The idea of spin-charge separation in cuprate superconductors has been recently energized by Senthil and Fisher who formulated a Z_2 gauge theory and, within its context, proposed a ``vison detection'' experiment as a test for topological order in a sample with multiply connected geometry. Here we show that the same experiment can be performed to test for the spin-charge separation in U(1) [but not in SU(2)] theory and argue that vortex core spectroscopy can in fact distinguish between the different symmetries of the fictitious gauge field. 
M. Franz and Z. Tesanovic (ITP)