Gravitational Collapse of a Rotating Cylindrical Null Shell in the   Cosmic String Spacetime
  We study the gravitational collapse of a rotating cylindrical null shell with flat interior and the metric of a spinning cosmic string as the exterior. We see that there is a critical radius, where the energy density of the shell vanishes and beyond which it would be negative, thereby signaling that the matching would be unphysical. 
S. Khakshournia
gr-qc