# Would a 5-dimensional black hole actually break laws of physics?

I discovered a paper by, Figueras, Kunesch, and Tunyasuvunakool, "End Point of Black Ring Instabilities and the Weak Cosmic Censorship Conjecture." A Cambridge University press release is here.

1. The press release says that this theory would 'break' laws of physics. But why between quotation marks? Would this theory really/literally break laws of physics? Even the most fundamental ones? Even invariances? Wouldn't the universe be destroyed if such naked singularity existed?

2. How can this theory really break laws of physics with a singularity by just taking GR to 5D, if the general consensus is that singularities that do break laws of physics cannot really exist and they do not make the equations of GR useless? What has this theory that allows it to do that if the other theories, when they predict such singularities, are considered to be wrong or incomplete? Why would this theory not be wrong?

3. At first I thought that to do so, the authors used some exotic theory of physics. But surprisingly, they used General Relativity but with the simple condition of being used in 5 Dimensions. If real singularities are thought to not exist in GR in our number of dimensions (3-4D), why would they really exist by simply going up to 5D?

4. It is not obvious that GR predicting singularities would be a problem because it is generally considered that singularities do not exist. Why would this theory claim that naked singularities exist? Is it that depending on the conditions of the universe where the black hole would exist, it would actually generate a singularity or not?

5. Last and most important question: If that singularity could actually exist and it actually broke GR, although we cannot predict what would happen in the universe after that, can we know whether, depending on the conditions of the black hole and the singularity, the singularity could break literally ALL fundamental conditions and laws (even invariances) allowing literally/really impossible things to happen (like time travel or a method to find a mathematical solution for factorizing number 181, which obviously cannot be factorized)?

• Don’t worry about gravitational singularities, either naked or clothed. They are an artifact of GR and are unlikely to occur in whatever theory of quantum gravity turns out to be correct. (Quantum effects will probably smear things out at the Planck scale and avoid a singularity.) In any case, the factorization of integers is not affected by any physics! Nov 14, 2018 at 0:03
• Incidentally, 181/128 is a nice binary approximation of $\sqrt2$. Nov 14, 2018 at 1:15
• @G.Smith "In any case, the factorization of integers is not affected by any physics!" But is there any way where the existence of this singularity would actually break all laws and even invariances (thus leaving a universe with "no rules" where we impossible things could happen like creating a brain capable of conceiving impossible things like factorising 181).
– user198758
Nov 15, 2018 at 21:22
• @G.Smith I mean: We cannot exactly predict what would happen if a 5 black hole naked singularity existed, but can we be sure that with othercertain degrees of freedom or certain conditions or certain types of black holes/singularities, the singularity would literally break everything (even invariances)?
– user198758
Nov 15, 2018 at 21:22
• @G.Smith or even if such a singularity existed would not necessarily mean that all laws (even the most fundamental ones or even invariances) would break, could it possibly do that? I mean, although not being necessary, could that be within the actual possibilities of what can such singularity do?
– user198758
Nov 15, 2018 at 21:22

The press release says that this theory would 'break' laws of physics. But why between quotation marks? Would this theory really/literally break laws of physics?

What the press release means, translated into technical terms, is that a violation of weak cosmic censorship would break the predictive power of general relativity because we would not have existence and uniqueness of solutions to problems in which the initial conditions are given.

How can this theory really break laws of physics with a singularity by just taking GR to 5D, if the general consensus is that singularities that do break laws of physics cannot really exist and they do not make the equations of GR useless?

Although most people expect GR's singularities to be tamed or eliminated by a hypothetical theory of quantum gravity, we don't know that that's the case (because we don't have a theory of quantum gravity), and it would be exciting/scary if a real-world process could produce a naked singularity, which would be observable to us and which would presumably amplify quantum gravity effects so that we could see them.

If real singularities are thought to not exist in GR in our number of dimensions (3-4D), why would they really exist by simply going up to 5D?

I don't know if there is a simple explanation for this, but basically there is an instability in 4+1 dimensions that is not present in 3+1 dimensions. This should not be too surprising, since there are other examples in physics where adding more degrees of freedom can create a new instability. For example, a house of cards may be stable, but if you make the cards soft so that they can flex, then it can become unstable.

It is not obvious that GR predicting singularities would be a problem because it is generally considered that singularities do not exist. Why would this theory claim that naked singularities exist?

They do exist in GR, which is a classical theory.

Last and most important question: If that singularity could actually exist and it actually broke GR, although we cannot predict what would happen in the universe after that, can we know whether, depending on the conditions of the black hole and the singularity, the singularity could break literally ALL fundamental conditions and laws (even invariances) allowing literally/really impossible things to happen (like time travel or a method to find a mathematical solution for factorizing number 181, which obviously cannot be factorized)?

Finding that a physical theory breaks down is not an existential crisis. It just means that the theory has limits.

• "Finding that a physical theory breaks down is not an existential crisis. It just means that the theory has limits." But is there any way where the existence of this singularity would actually break all laws and even invariances (thus leaving a universe with "no rules"). I mean: We cannot exactly predict what would happen if a 5 black hole naked singularity existed, but can we be sure that with othercertain degrees of freedom or certain conditions or certain types of black holes/singularities, the singularity would literally break everything (even invariances)? @BenCrowell
– user198758
Nov 14, 2018 at 22:24
• or even if such a singularity existed would not necessarily mean that all laws (even the most fundamental ones or even invariances) would break, could it possibly do that? I mean, although not being necessary, could that be within the actual possibilities of what can such singularity do? @BenCrowell
– user198758
Nov 15, 2018 at 0:33
• Think about this analogy: we throw a dice 1000 times. We want to get number 1 those 1000 times in a row and we cannot predict what number we will get. Throwing a dice does not necessarily mean that number 1 would repeat 1000 times in a row (and it is practically impossible). But it could POSSIBLY happen. Could this be applied to such singularity? Could it POSSIBLY break all laws (even the most fundamental ones and even invariances) and thus leaving a universe "without rules"? Although we cannot predict what the singularity would do, could this POSSIBLY happen? @BenCrowell
– user198758
Nov 15, 2018 at 0:36