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| {{Expert-subject|Science|date=October 2008}}
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| In [[general relativity]], a '''naked singularity''' is a [[gravitational singularity]] without an [[event horizon]]. In a [[black hole]], the singularity is completely enclosed by a boundary known as the [[event horizon]], inside which the gravitational force of the singularity is strong enough so that light cannot escape. Hence, objects inside the event horizon—including the singularity itself—cannot be directly observed. A naked singularity, by contrast, is observable from the outside.
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| 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''. It would also cause foundational problems for general relativity, because general relativity cannot make predictions about the future evolution of [[space-time]] near a singularity. In generic black holes, this is not a problem, as an outside viewer cannot observe the space-time within the event horizon.
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| Some research has suggested that if [[loop quantum gravity]] is correct, then naked singularities could exist in nature,<ref>M. Bojowald, Living Rev. Rel. 8, (2005), 11 (http://relativity.livingreviews.org/Articles/lrr-2008-4/)</ref><ref>R. Goswami & P. Joshi, Phys. Rev. D, (2008) (http://arxiv.org/abs/gr-qc/0608136)</ref><ref>R. Goswami, P. Joshi, & P. Singh, Phys. Rev. Letters, (2006), 96 (http://arxiv.org/abs/gr-qc/0506129)</ref> implying that the [[cosmic censorship hypothesis]] does not hold. Numerical calculations<ref>D. Eardley & L. Smarr, Phys. Rev. D., (1979), 19, (http://prola.aps.org/abstract/PRD/v19/i8/p2239_1)</ref> and some other arguments<ref>A. Krolak, Prog. Theor. Phys. Supp., (1999) 136, 45, (http://ptp.ipap.jp/link?PTPS/136/45/)</ref> have also hinted at this possibility.
| | The federal two-island-nation expects to acquire banker assistance in restructuring its public debt stock, which will be reported to be an overall total of approximately $1billion. However, treasury bills aren't an integral part of the plan.<br><br>The third action would be to develop a relationship together with your customers as if they personally went during your door. They should become familiar with you, understand what you've to supply, and trust you.<br><br>People like to-do business with who they know, like and trust. They also want to do business with people that give excellent material and have management skills. That's why marketing oneself is so very important to getting leads online. Each person has their own account. Something could be quickly copied. It's impossible to replicate an individual.<br><br><br><br>Do not beat round the bush as it pertains to your articles - talk numbers and facts. Clarify your offer in a clear and quick way. People like to know without studying an excessive amount of, why you have delivered the email. When possible put a topic to the envelope so the person understands what the email is all about. Keep the content brief and succinct. If there is an excessive amount of wording, then break the monotony with the usage of appealing graphics and photographs.<br><br>A big occasion [http://hmccap.com/wp-content/uploads/team/managing/juan-pablo-schiappacasse_esp.html jaun pablo schiappacasse canepa] method is not for all, particularly when you have limited assets. Stick with what is most effective for your advertising strategy.<br><br>If I write an excellent article that's beneficial to my group and it gets syndicated, I will get several links for this one article, instead of just the one at the bottom within the resource box.<br><br>Though some of these items might seem simplistic, you would be surprised how many times we disregard the simplest ways to get our names out there in front of prospective visitors. Utilize The internet's resources to greatly help boost your revenue and spread the word about your experiences! |
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| To this date, no naked singularities (and no event horizons) have been observed.
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| ==Predicted formation==
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| From concepts drawn of [[rotating black hole]]s, 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.
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| A singularity rotating fast enough might be created by the collapse of dust or by a supernova of a fast-spinning star. Studies of [[pulsar]]s{{Citation needed|date=April 2007}} and some computer simulations (Choptuik, 1997) have been performed.
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| This is 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.
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| This model also ignores the relativistic aspects of singularity formation. Such a process involves relativistic effects that cause an asymptotic slowing of time compared to the universe at large. To ''see'' a singularity or event horizon ''form'' a collapsing mass would have to be observed for far longer than the longest conceivable life-span for a universe like ours. Spinning the collapsing mass in an attempt to create a ''naked singularity'' does nothing to get around the relativistic time-dilation observed by the universe that we inhabit. Simply put, while mathematically possible, {{According to whom|there are not now, and never can be, actual event horizons or singularities in any part of the observable universe|date=January 2014}}.
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| ==Metrics==
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| Disappearing event horizons exist in the [[Kerr metric]], which is a spinning black hole in a vacuum. Specifically, if the [[angular momentum]] is high enough the event horizons will disappear. Transforming the Kerr metric to [[Boyer-Lindquist coordinates]], it can be shown<ref>Hobson, et. al, General Relativity an Introduction for Physicists, Cambridge University Press 2007, p. 300-305</ref> that the <math>r</math> coordinate (which is not the radius) of the event horizon is
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| <math>r_{\pm}= \mu \pm (\mu^{2}-a^{2})^{1/2}</math>,
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| where <math>\mu = G M / c^{2}</math>, and <math>a=J/M c</math>. In this case, "event horizons disappear" means when the solutions are complex for <math>r_{\pm}</math>, or <math>\mu^{2} < a^{2}</math>.
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| Disappearing event horizons can also be seen with the [[Reissner–Nordström metric|Reissner-Nordström]] geometry of a charged black hole. In this metric it can be shown<ref>Hobson, et. al, General Relativity an Introduction for Physicists, Cambridge University Press 2007, p. 320-325</ref> that the singularities occur at
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| <math>r_{\pm}= \mu \pm (\mu^{2}-q^{2})^{1/2}</math>,
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| where <math>\mu = G M / c^{2}</math>, and <math>q = G Q^{2}/(4 \pi \epsilon_{0} c^{4})</math>. Of the three possible cases for the relative values of <math>\mu</math> and <math>q</math>, the case where <math>\mu^{2} < q^{2}</math> causes both <math>r_{\pm}</math> to be complex. This means the metric is regular for all positive values of <math>r</math>, or in other words the singularity has no event horizon.
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| See [[Kerr-Newman metric]] for a spinning, charged ring singularity.
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| ==Effects==
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| 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.<ref>{{cite news |url=http://space.newscientist.com/article/dn12707-is-a-naked-singularity-lurking-in-our-galaxy.html |author=Stephen Battersby |title=Is a 'naked singularity' lurking in our galaxy? |date=1 October 2007 |accessdate=2008-03-06 |publisher=[[New Scientist]]}}</ref>
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| ==Cosmic censorship hypothesis==
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| The [[cosmic censorship hypothesis]] says that a naked singularity cannot arise in our universe from realistic initial conditions.
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| ==In fiction==
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| *[[M. John Harrison]]'s [[Kefahuchi Tract]] trilogy of [[science fiction]] novels ([[Light (novel)|Light]], [[Nova Swing]] and [[Empty Space]]) centre upon humanity's exploration of a naked singularity.
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| *"Dark Peril" by [[James C. Glass]] (published in [[Analog Science Fiction and Fact|Analog]] March, 2005), is a story about space travelers on an exploratory mission. While they investigate a strange cosmological phenomenon, their two small space crafts begin to shake, and they are unable to leave the area. One crew member realizes that they are trapped in the [[Ergosphere]] of a [[black hole]] or [[naked singularity]]. The story describes a cluster of multiple black holes or singularities, and what the crew does to try to survive this seemingly inescapable situation.
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| ==See also==
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| *[[Black hole electron]]
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| *[[List of astronomical topics]]
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| *[[List of physics topics]]
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| ==References==
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| {{Reflist}}
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| ==External links==
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| *[http://xstructure.inr.ac.ru/x-bin/theme3.py?level=1&index1=203038 Naked singularity] on [[arXiv]]
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| *M. C. Werner and A. O. Peters, [http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRVDAQ000076000006064024000001&idtype=cvips&gifs=yes "Magnification relations for Kerr lensing and testing cosmic censorship"], ''Physical Review D'', Vol. 76, Issue 6 (2007).
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| *Pankaj S. Joshi, [http://www.sciam.com/article.cfm?id=naked-singularities "Do Naked Singularities Break the Rules of Physics?"], ''Scientific American'', January 2009.
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| *Marcus Chown, [http://www.newscientist.com/article/mg20327204.700-fastspinning-black-holes-might-reveal-all.html "Fast-spinning black holes might reveal all"] ''New Scientist'', August 2009.
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| {{Black holes}}
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| {{DEFAULTSORT:Naked Singularity}}
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| [[Category:Black holes]]
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