Ray trajectories for a spinning cosmic string and a manifestation of
  self-cloaking
  A study of ray trajectories was undertaken for the Tamm medium which
represents the spacetime of a cosmic spinning string, under the
geometric-optics approximation. Our numerical studies revealed that: (i) rays
never cross the string's boundary; (ii) the Tamm medium supports evanescent
waves in regions of phase space that correspond to those regions of the
string's spacetime which could support closed timelike curves; and (iii) a
spinning string can be slightly visible while a non-spinning string is almost
perfectly invisible.
