Naked singularity

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In general relativity, a naked singularity is a gravitational singularity without an event horizon. The singularities inside black holes are always surrounded by an area which does not allow light to escape, and therefore cannot be directly observed. A naked singularity, by contrast, is observable from the outside.

The theoretical existence of naked singularities is important because their existence would mean that it would be possible to observe the collapse of an object to infinite density.

Some research has suggested that if loop quantum gravity is correct, then naked singularities could exist in nature,^[1][2][3] implying that the cosmic censorship hypothesis does not hold. Numerical calculations^[4] and some other arguments^[5] have also hinted at this possibility.

Contents 1 Predicted formation 2 Effects 3 In fiction 4 See also 5 References 6 External links

[edit] Predicted formation

From concepts drawn of rotating black holes, it is shown that a singularity, spinning rapidly, can become a ring-shaped object. This results in two event horizons, as well as an ergosphere, which draw closer together as the spin of the singularity increases. When the outer and inner event horizons merge, they shrink toward the rotating singularity and eventually expose it to the rest of the universe.

A singularity rotating this fast might be created by the collapse of dust or by a supernova of a fast-spinning star. Studies of pulsars^{[citation needed]} and some computer simulations (Choptuik, 1997) have been performed.

This is, of course, an example of a mathematical difficulty (divergence to infinity of the density) which reveals a more profound problem in our understanding of the relevant physics involved in the process. A workable theory of quantum gravity should be able to solve problems such as these.

[edit] Effects

A naked singularity could allow scientists to observe an infinitely dense material, which would under normal circumstances be impossible by the cosmic censorship hypothesis. Without an event horizon of any kind, some speculate that naked singularities could actually emit light.^[6]

Because no such objects have been found in the universe, and no such effects have been observed, many scientists are convinced that a theory of quantum gravity that coincides with the Standard Model would disallow such objects to come into being.

[edit] In fiction

• A naked singularity almost appears in the six episode OAV series Diebuster. In the final episode, a black hole's event horizon is somehow breached when struck by a powerful force. It is stated that this "crack" would eventually lead to the singularity inside being exposed to the universe. In the same scene, one character speculates that the Big Bang was the aftermath of such an event.

• A Naked Singularity plays a key part in Peter Hamilton's Night's Dawn trilogy, in particular in the Third book, "The Naked God". In this case, it is an observable, light-emitting 'structure' built by an intelligent race.

• In Ring by Stephen Baxter, the Big Dumb Object in the title is a rapidly rotating galaxy-sized object whose center acts as a gateway to other universes.

• In Marco's Millions, a naked singularity threatens to destroy Earth's universe.

• In Eon by Greg Bear, the flaw is a man-made singularity inside the seventh (and last) chamber of a big asteroid known as Thistledown, stretching the seventh chamber into infinity with the flaw in the center. This infinite corridor is known as The Way from which it is possible to open gates to other universes.

• In the two-part Battlestar Galactica series finale, "Daybreak", the Cylon Colony is located in orbit around a naked singularity. The show's Science advisor; however, stated it was more in common with a black hole, but the production staff wanted to avoid public misconceptions about the nature of black holes.

[edit] See also

• List of astronomical topics
• List of physics topics

[edit] References

1. ^ M. Bojowald, Living Rev. Rel. 8, (2005), 11 (http://relativity.livingreviews.org/Articles/lrr-2008-4/)
2. ^ R. Goswami & P. Joshi, Phys. Rev. D, (2008) (http://arxiv.org/abs/gr-qc/0608136)
3. ^ R. Goswami, P. Joshi, & P. Singh, Phys. Rev. Letters, (2006), 96 (http://arxiv.org/abs/gr-qc/0506129)
4. ^ D. Eardley & L. Smarr, Phys. Rev. D., (1979), 19, (http://prola.aps.org/abstract/PRD/v19/i8/p2239_1)
5. ^ A. Krolak, Prog. Theor. Phys. Supp., (1999) 136, 45, (http://ptp.ipap.jp/link?PTPS/136/45/)
6. ^ Stephen Battersby (1 October 2007). "Is a 'naked singularity' lurking in our galaxy?". New Scientist. http://space.newscientist.com/article/dn12707-is-a-naked-singularity-lurking-in-our-galaxy.html. Retrieved on 2008-03-06. 

[edit] External links

• Naked singularity on arXiv
• M. C. Werner and A. O. Peters, "Magnification relations for Kerr lensing and testing cosmic censorship", Physics Review D, Vol. 76, Issue 6 (2007).
• Pankaj S. Joshi, "Do Naked Singularities Break the Rules of Physics?", Scientific American, January 2009.