A new study by researchers from the University of Cambridge shows how a strangely shaped black hole could "break" Einstein's general theory of relativity, although they claim that the only way that such an interstellar object could exist is in a universe with five or more dimensions.
Using a computer simulation, the team proposed a black hole shaped like a very thin ring that gives rise to a series of "bulges," which are attached to strings and, as time goes by, become thinner. Eventually, they become so thin that they pinch off into a series of miniature black holes much in the same way as a stream of water from a tap breaks up into droplets.
Although ring-shaped black holes were proposed by theoretical physicists in 2002, this marks the first time that their dynamics have been simulated using supercomputers. Furthermore, the new simulations reveal that if this black hole were to form, it would create a "naked singularity" causing the equations at the core of general relativity to break down.
Singularities are points of gravity that are so intense that space, time and the laws of physics break down. General relativity predicts that they exist at the center of black holes, surrounded by an event horizon, the "point of no return," making their observation from the outside impossible.
"As long as singularities stay hidden behind an event horizon, they do not cause trouble and general relativity holds - the 'cosmic censorship conjecture' says that this is always the case," Markus Kunesch, co-author of the study, said in a press release. "As long as the cosmic censorship conjecture is valid, we can safely predict the future outside of black holes. Because, ultimately, what we're trying to do in physics is to predict the future given knowledge about the state of the universe now."
However, if a singularity existed outside of an event horizon, it would represent an object that has collapsed to a state of infinite density, causing the laws of physics to break down. Physicists predict that this event, called a naked singularity, could exist in higher dimensions.
"If naked singularities exist, general relativity breaks down," said co-author Saran Tunyasuvunakool. "And if general relativity breaks down, it would throw everything upside down because it would no longer have any predictive power - it could no longer be considered as a standalone theory to explain the universe."
Using supercomputer simulations, the team was able to demonstrate that if the ring is thin enough on a ring-shaped black hole, it could lead to the formation of naked singularities.
"The better we get at simulating Einstein's theory of gravity in higher dimensions, the easier it will be for us to help with advancing new computational techniques - we're pushing the limits of what you can do on a computer when it comes to Einstein's theory," said Tunyasuvunakool. "But if cosmic censorship doesn't hold in higher dimensions, then maybe we need to look at what's so special about a four-dimensional universe that means it does hold."
The findings will be released in the journal Physical Review Letters.
