In our four dimensional universe (length, width, height, spacetime), a ring shaped black hole would collapse into a sphere; therefore, it contains the singularity past the event horizon. The simulation performed was of a ring shaped black hole in a five dimensional universe, in which the ring doesn't collapse but instead forms “bulges or waves” in the ring. The bulges are connected to each other through small strings of matter. “When the thin strings of this ring separate, like a small stream of water splitting into droplets,” the unstable singularities are displayed outside the event horizon (University of Cambridge). This is known as a naked singularity.
When the singularities are displayed outside of the event horizon, the theory of relativity is broken. Again, the simulation occurred in a universe with five or more dimensions. This would be impossible to complete in our universe as it would collapse.
These scientists are still trying to understand why singularities in front of the event horizon are impossible in a 4D universe but possible in a 5D universe. Hopefully they will be able to start understanding this in the near future.
Works Cited
University of Cambridge. "Five-dimensional black hole could 'break' general relativity." ScienceDaily.
ScienceDaily, 18 February 2016. http://tinyurl.com/5Dblackhole 2016/02/160218144910.htm