"The researchers, from the University of Cambridge and Queen Mary University of London, have successfully simulated a black hole shaped like a very thin ring, which gives rise to a series of 'bulges' connected by strings that become thinner over time. These strings eventually become so thin that they pinch off into a series of miniature black holes, similar to how a thin stream of water from a tap breaks up into droplets.
Ring-shaped black holes were 'discovered' by theoretical physicists in 2002, but this is the first time that their dynamics have been successfully simulated using supercomputers. Should this type of black hole form, it would lead to the appearance of a 'naked singularity', which would cause the equations behind general relativity to break down. The results are published in the journal Physical Review Letters."
"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," said study co-author Markus Kunesch, a PhD student at Cambridge's Department of Applied Mathematics and Theoretical Physics (DAMTP). "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."
But what if a singularity existed outside of an event horizon? If it did, not only would it be visible from the outside, but it would represent an object that has collapsed to an infinite density, a state which causes the laws of physics to break down. Theoretical physicists have hypothesised that such a thing, called a naked singularity, might exist in higher dimensions.
"If naked singularities exist, general relativity breaks down,"
What the Cambridge researchers, along with their co-author Pau Figueras from Queen Mary University of London, have found is that if the ring is thin enough, it can lead to the formation of naked singularities.
http://phys.org/news/2016-02-five-dimensional-black-hole-relativity.html
http://dx.doi.org/10.1103/PhysRevLett.116.071102
The situations like that are simply saved by adding the Dark Matter term to the left hand of Einstein Equations. See my pub:
Book Simplest Explanation of Dark Matter and Dark Energy
No. General relativity implies that singularities are generic; it doesn't imply that they are always hidden behind an event horizon, though this was found so often that Penrose formulated the ``cosmic censorship conjecture'' that makes, precisely, such a statement. However this conjecture doesn't affect the validity of general relativity. So the statement quoted isn't correct. In particular, if naked singularities exist, general relativity does not break down; nothing happens that's not supposed to happen and the singularities appear where expected-the cosmic censorship conjecture is not a postulate of general relativity. In addition, the fact that its putative violation is found in five spacetime dimensions and, perhaps, higher, implies that the relevance for physical processes, that take place in four spacetime dimensions, remain to be understood. Not to mention the fact that the numerical results themselves require some care-they can only provide finite numbers, in any case, so whether, indeed, the singularity is naked, or the horizon of such a size that the numerics can't resolve it-or whether a new structure appears-remains to be worked out. For it's by no means obvious whether the ``naked singularity'' proposed is stable under perturbations.
Indeed examples of naked singularities,i.e. counterexamples to cosmic censorship, aren't rare, in four dimensions, already:
http://projecteuclid.org/download/pdf_1/euclid.cmp/1103859409
and https://projecteuclid.org/download/pdf_1/euclid.cmp/1103859810
So a nice piece of work, but nothing as shattering as the news have made it out.
The cosmic censorship conjecture is a conjecture-it's been proven in certain cases, shown not to hold in others; therefore it's definitely not a ``failure''. Black holes are classical objects, so the notion of quantum vacuum must be used with care. In particular, the vacuum of quantum excitations isn't uniquely defined in curved spacetime-and that was discovered by Hawking forty years ago. That matter can be described as excitations of a vacuum state is well known for even longer-at least since Dirac introduced creation and annihilation operators in 1927.
However the objects discussed in the publication of this thread are classical objects in five spacetime dimensions.
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