Timeline for Naked singularity
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Jan 22, 2021 at 4:02 | comment | added | apt45 | This answer has nothing to do with the OP. The user is correctly doing a perfect analogy. The Coulomb potential generated by an electron diverges at $r=0$, and the divergence tells us that our effective field theory breaks down. A new theory must be used at this point, indeed we have discovered Quantum Mechanics. The OP just asks why we cannot think of naked singularities in this same way as Coulomb potential singularities. | |
| Dec 14, 2018 at 20:37 | comment | added | user4552 | Cham has asked a question on this topic: physics.stackexchange.com/questions/447308/… | |
| Dec 14, 2018 at 20:32 | comment | added | John Rennie | @JerrySchirmer I think there is some confusion about precisely how to define a naked singularity, so to an extend the argument is about terminology. | |
| Dec 14, 2018 at 20:25 | comment | added | Zo the Relativist | Or, at least, it's a naked singularity in the sense that it has no horizon, and can be reached by geodesics that go to timlike infinity. | |
| Dec 14, 2018 at 18:20 | comment | added | Zo the Relativist | The big bang is a naked singularity, and yes, we can't extend any predictability to the past of the big bang at all, just like you can't extend future predictibility from, say, a $a > M$ Kerr solution. | |
| Dec 14, 2018 at 13:25 | comment | added | Cham | @MBN, could you elaborate why the Big Bang isn't a naked singularity? AFAIK, it could be "seen", theoretically. | |
| Dec 14, 2018 at 9:47 | comment | added | MBN | @Cham : The big bang is not a naked singularity. And when you remove the singularity from the manifold (more accurately it was never a part of the manifold) you don't always get a globally hyperbolic space-time. | |
| Dec 13, 2018 at 16:18 | comment | added | John Rennie | @Cham yes, I agree, though I suspect this is going beyond what the OP was asking about. | |
| Dec 13, 2018 at 15:20 | comment | added | Cham | Yes, I agree that the Big Bang is a spacelike singularity. But it is "removed" from the manifold (like most singularities) so of course the manifold is globally hyperbolic. But the Big Bang is still a naked singularity out of which everything came out. This is the kind of "troubles" we could get from a naked singularity, like the Reisner-Nordstrom solution with $Q > M$ for example (if I remember well, there's a gravitational repulsion, close to the naked singularity in this case). | |
| Dec 13, 2018 at 14:45 | comment | added | user4552 | @Cham: A spacetime is globally hyperbolic if (1) strong causality holds (essentially no CTCs), and (2) $\forall p$, $q$, the future timelike light cone of $p$ intersected with the past timelike light cone of $q$ is compact. By this definition, cosmological spacetimes are globally hyperbolic, despite the presence of the big bang singularity. That means we have predictability, in the sense of existence and uniqueness for Cauchy problems. You can define the big bang as a naked singularity if you like, but what matters is that it's not timelike. | |
| Dec 13, 2018 at 12:30 | comment | added | Cham | Isn't the Big Bang a naked singularity? The whole universe got out of that singularity, and of course it wasn't "predictible"! | |
| Dec 13, 2018 at 9:13 | history | answered | John Rennie | CC BY-SA 4.0 |