16

I recently came across the interesting statement that most definitions of cosmic censorship (CC), and most work on proving it, don't exclude something that Hawking calls a "thunderbolt" (Penrose 1978, Hawking 1993, Penrose 1999). Penrose gives a verbal description as follows.

... censorship proposals [of a certain] nature ... do not ... eliminate the possibility of what Hawking (1993) refers to as thunderbolts, first considered in Penrose (1978). This is the hypothetical situation according to which a gravitational collapse results in a 'wave of singularity' coming out from the collapse region, which destroys the universe as it goes! On this picture, the entire space-time could remain globally hyperbolic since everything beyond the domain of dependence of some initial hypersurface is cut off (‘destroyed’) by the singular wave. An observer, whether at infinity or in some finite location in the space-time, is destroyed just at the moment that the singularity would have become visible[...]

For convenience, I'm going to state the relevant technical definitions here:

  • $S$ - past set, a set whose causal past $J^-(S)$ is the same as itself;

  • $IP$ - indecomposable past set, a past set that is not the union of two past sets;

  • $PIP$ - proper $IP$, an $IP$ that equals $J^-(x)$ for a single point $x$;

  • $TIP$ - $IP$ that isn't a $PIP$, also known as an "ideal point";

  • $TIP_\infty$ - $TIP$, generated by a timelike curve, that extends infinitely far into the future;

  • $TIP_S$ - singular $TIP$, that is not an $TIP_\infty$.

One possible statement of cosmic censorship is that no $TIP_\infty$ contains a $TIP_S$. This particular definition does rule out thunderbolts. Penrose 1999 discusses the interpretation a little, and gives the impression that this statement of CC may be strong and therefore too hard for people to make progress on.

Has any progress been made since 1999 on proving any version of CC that rules out thunderbolts?

Please accept my apologies in advance if a Penrose thunderbolt wipes us out before I can upvote your helpful answer.

Sources:

  • Penrose (1978). Theoretical principles in astrophysics and relativity, eds. Liebowitz et al.

  • Hawking (1993).The rennaissance of General relativity" (in honour of D. W. Sciama), eds. Ellis et al.

  • Penrose (1999).The Question of Cosmic Censorship, J. Astrophys. Astr. 20 (1999), 233–248

Emilio Pisanty
  • 132,859
  • 33
  • 351
  • 666

1 Answers1

1

The most recent paper I've come across is this one: http://arxiv.org/abs/arXiv:1011.6442.

Surprises in the Evaporation of 2-Dimensional Black Holes by Abhay Ashtekar, Frans Pretorius, Fethi M. Ramazanoğlu

Journal reference: Phys.Rev.Lett.106:161303,2011

DOI: 10.1103/PhysRevLett.106.161303

They see NO "thunderbolts". But this is 2d, I don't know if the results extend to 4d or not.

Curious George
  • 648
  • 4
  • 9
  • This is semi-classical. – MBN Sep 07 '13 at 08:33
  • What can I do about it? – Curious George Sep 07 '13 at 10:23
  • 1
    Nothing, I am just commenting. The way I understand it, the question is for the progress in classical(non-quantum) general relativity. – MBN Sep 07 '13 at 10:31
  • I don't see any connection between this paper and the question ...? –  Sep 07 '13 at 16:04
  • If you search in the text you'll find that they comment on the issue: – Curious George Sep 07 '13 at 17:44
  • End of page 3 of the preprint: on the last ray, our simulations showed that curvature remains finite. Thus, contrary to wide spread belief, based in part on [3], and in contrast to simplified and soluble models, there is no ‘thunderbolt singularity’ in the metric. Where [3] is arXiv:hep-th/9207105. But I didn't read carefully the question, I just wanted to report this recent paper. I initially even thought that @MBN was complaining that they didn't performed a full Quantum Gravity computation ;) – Curious George Sep 07 '13 at 17:53
  • Well I meant "didn't perform" – Curious George Sep 07 '13 at 18:03
  • OK, just in case you think is interesting anyway, they have a more detailed paper: http://arxiv.org/abs/1012.0077 – Curious George Sep 07 '13 at 18:45
  • Ah, I see -- thanks for the further explanation. This is interesting, although it's one very, very special situation in 2 dimensions. –  Sep 10 '13 at 01:02