Collapse of a Rotating Shell in 3+1 Dimensions

Synopsis

We consider a rotating thin shell which is on the boundary between a near horizon extremal Kerr spacetime and a static near horizon spacetime.  The matter on the shell is taken to be described by the stress-energy tensor of an anisotropic fluid. We show that the shell does not collapse through the horizon of the outer geometry.  (Work in conjunction with S. Kloster)