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บรรทัด 373:
พฤติกรรมคล้ายหลุมดำเนื่องจากเอดีเอสและซีเอฟทีระหว่างทฤษฎีของแรงนิวเคลียร์ที่รุนแรงไม่มีอะไรเกี่ยวข้องกับทฤษฎีแรงโน้มถ่วงและทฤษฎีแรงโน้มถ่วงควอนตัม ทฤษฎีเหล่านี้คล้ายกันเพราะใช้อธิบาย[[ทฤษฎีสตริง]] ดังนั้นการก่อตัวและความไม่ต่อเนื่องของ ควาร์ก-กลูออน พลาสมานั้นก็เกี่ยวข้องกับการเกิดหลุมดำ ลูกไฟที่ [[Relativistic Heavy Ion Collider]] [RHIC] เป็นปรากฏการณ์ที่อาจเทียบได้กับหลุมดำ และคุณสมบัติส่วนใหญ่จะทำให้ได้อย่างถูกต้องโดยใช้การเปลี่ยนเทียบนี้ อย่างไรก็ดี ลูกไฟนี้ไม่ใช่วัตถุโน้มถ่วง และก็ยังไม่ทราบแน่ชัดว่าจะมีพลังงานมากกว่าที่เครื่องเร่งอนุภาค[[Large Hadron Collider]] [LHC] จะสามารถสร้างหลุมดำจิ๋วขึ้นมาตามทฤษฎีหรือไม่<ref>See [[Safety of particle collisions at the Large Hadron Collider]] for a more in depth discussion.</ref>
==ประวัิติของหลุมดำ==
จากแนวคิดนิวตันของมิเชลและ่[[ลาปลาส]]นั้นมักจะกล่าวถึงดาวมืด เพื่อที่จะแยกออกจากทฤษฎีสัมพัทธภาพของหลุมดำ
===ทฤษฎีของนิวตัน===
ในปี 1783 นักธรณีวิทยาชื่อ จอห์น มิเชล(John Michell)ได้เขียนจดหมายถึง เฮนรี่ คาเวนดิช(Henry Cavendish) กล่าวถึงแนวความคิดเกี่ยวกับวัตถุที่มีขนาดใหญ่มากที่ไม่สามารถที่จะหนีออกจากขึ้นบรรยาการได้ ซึ่งแนวคิดนี้ก็ได้รับการตีพิมพ์ในเวลาต่อมา<ref name = "Michell1784"/>
{{cquote|''ถ้ามีทรงกลมที่มีความหนาแน่น และเส้นผ่านศูนย์กลางเหมือนดวงอาทิตย์และเป็นสัดส่วนต่อกัน 500 ต่อ 1 มีวัตถุตกลงจากความสูงที่มีค่าอนันต์ก็จะมีความเร็วมากกว่าแสงและสมมติว่าแสงนั้นถูกดึงดูดโดยแรงบางอย่างที่เป็นสัดส่วนกับแรงภายในของตัวมันเอง จะทำให้แสงแผ่รังสีจากวัตถุที่จะย้อนกลับมาจากแรงโน้มถ่วงที่เหมาะสม''}}
นี่เป็นข้อสรุปว่าแสงจะได้รับอิทธิพลจากความโน้มถ่วงเหมือน ๆ กับวัตถุขนาดใหญ่
ในปี 1796 นักคณิตศาสตร์ชื่อ ปิแอร์ ไซมอน ลาปลาส ได้เสนอแนวคิดเดียวกันในหนังสือที่จัดพิมพ์ครั้งที่หนึ่งและสองของเขา ชื่อ ''Exposition du système du Monde''
แนวความคิดเกี่ยวกับหลุมดำได้ถูกเพิกเฉยในศตวรรษที่ 19 นับตั้งแต่มีการกล่าวว่าแสงเป็นคลื่นที่ไม่มีมวล และไม่ได้รับอิทธิพลจากความโน้มถ่วง ไม่เหมือนกับหลุมดำในปัจจุบันที่มีวัตถุด้านหลังขอบฟ้าที่ยืนยันว่าจะยังคงที่อยู่แม้จะเกิดการยุบตัว
===ทฤษฎีเกี่ยวกับสัมพัทธภาพทั่วไป===
ในปี 1915 [[อัลเบิร์ต ไอน์สไตน์]] ได้พัฒนาทฤษฎีเกี่่ยวกับความโน้มถ่วงเรียกว่าสัมพัทธภาพทั่วไป ซึ่งในตอนแรกพบว่าแรงโน้มถ่วงมีผลกระทบกับแสง เม้ว่าจะถือว่าแสงมีมวลเป็นศูนย์ก็ตาม แต่ความจริงแล้วแหล่งกำเนิดของสภาพโน้มถ่วงนั้นไม่ใช่เกิดจากสภาพสมดุลแต่เกิดจากพลังงาน หลังจากนั้นไม่กี่เดือน คาร์ล ชวาร์สชิลด์ ได้เสนอมาตราชวาร์สชิลด์ สำหรับสนามโน้มถ่วงของมวลที่เป็นจุดและมวลทรงกลม<ref name ="Schwarzschild1916"/> ที่แสดงว่าหลุมดำมีอยู่จริง รังสีชวาร์สชิลด์นั้นเป็นที่รู้จักกันว่าเป็นรัศมีของขอบฟ้าเหตุการณ์ของหลุมดำที่ไม่หมุน แต่ผู้คนยังไม่เข้าใจกันในตอนนั้น ตัวอย่างเมื่อชวาร์สชิลด์คิดว่ามันไม่เป็นทางกายภาพ โจอันนาส โดรสเต นักศึกษาของเฮนดริก ลอว์เรนซ์ ได้ให้คำตอบเดียวกันสำหรับมวลที่เป็นจุดในหลายเดือนต่อมา หลังจากที่ชวาร์สชิลด์เสนอแนวคิด และได้เพิ่มเติมคุณสมบัติบางประการอีกด้วย
In 1930, the [[astrophysicist]] [[Subrahmanyan Chandrasekhar]] argued that, according to [[special relativity]], a non-rotating body above 1.44 solar masses (the [[Chandrasekhar limit]]), would collapse since there was nothing known at that time could stop it from doing so. His arguments were opposed by [[Arthur Eddington]], who believed that something would inevitably stop the collapse. Eddington was partly right: a [[white dwarf]] slightly more massive than the Chandrasekhar limit will collapse into a [[neutron star]]. But in 1939, [[Robert Oppenheimer]] published papers (with various co-authors) which predicted that stars above about three solar masses (the [[Tolman-Oppenheimer-Volkoff limit]]) would collapse into black holes for the reasons presented by Chandrasekhar.<ref>[http://prola.aps.org/abstract/PR/v55/i4/p374_1 On Massive Neutron Cores], J. R. Oppenheimer and G. M. Volkoff, ''Physical Review'' '''55''', #374 (15 February 1939), pp. 374–381.</ref>
Oppenheimer and his co-authors used [[Schwarzschild metric|Schwarzschild's system of coordinates]] (the only coordinates available in 1939), which produced [[mathematical singularity|mathematical singularities]] at the [[Schwarzschild radius]], in other words the equations broke down at the Schwarzschild radius because some of the terms were [[infinity|infinite]]. This was interpreted as indicating that the Schwarzschild radius was the boundary of a "bubble" in which time "stopped". For a few years the collapsed stars were known as "frozen stars" because the calculations indicated that an outside observer would see the surface of the star frozen in time at the instant where its collapse takes it inside the Schwarzschild radius. But many physicists could not accept the idea of time standing still inside the Schwarzschild radius, and there was little interest in the subject for over 20 years.
In 1958 [[David Finkelstein]] broke the deadlock over "stopped time" and introduced the concept of the [[event horizon]] by presenting the [[Eddington-Finkelstein coordinates]], which enabled him to show that "The Schwarzschild surface r = 2 m is not a singularity but acts as a perfect unidirectional membrane: causal influences can cross it but only in one direction".<ref>D. Finkelstein (1958). "Past-Future Asymmetry of the Gravitational Field of a Point Particle". Phys. Rev. 110: 965–967. </ref> Note that at this stage all theories, including Finkelstein's, covered only non-rotating, uncharged black holes.
In 1963 [[Roy Kerr]] extended Finkelstein's analysis by presenting the [[Kerr metric]] (coordinates) and showing how this made it possible to predict the properties of [[rotating black hole]]s.<ref>{{cite web|url=http://prola.aps.org/abstract/PRL/v11/i5/p237_1|title=R. P. Kerr, "Gravitational field of a spinning mass as an example of algebraically special metrics", ''Phys. Rev. Lett.'' '''11''', 237 (1963)}}</ref> In addition to its theoretical interest, Kerr's work made black holes more believable for astronomers, since black holes are formed from stars and all known stars rotate.
In 1967 astronomers discovered [[pulsars]], and within a few years could show that the known pulsars were rapidly rotating [[neutron star]]s. Until that time, neutron stars were also regarded as just theoretical curiosities. So the discovery of pulsars awakened interest in all types of ultra-dense objects that might be formed by gravitational collapse.
In 1970, [[Stephen Hawking]] and [[Roger Penrose]] proved that black holes are a feature of all solutions to Einstein's equations of gravity, not just of Schwarzschild's, and therefore black holes cannot be avoided in some collapsing objects.<ref name="predicted">The Singularities of Gravitational Collapse and Cosmology. S. W. Hawking, R. Penrose, Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 314, No. 1519 (27 January 1970), pp. 529–548</ref>
In 1971, [[Louise Webster]] and [[Paul Murdin]], at the [[Royal Greenwich Observatory]],<ref>{{cite journal
| last=Webster | first=B. Louise | coauthors=Murdin, Paul
| title=Cygnus X-1—a Spectroscopic Binary with a Heavy Companion?
| journal=Nature | year=1972
| volume=235 | issue=2 | pages=37–38
| url=http://www.nature.com/nature/journal/v235/n5332/abs/235037a0.html
| accessdate=2008-03-10 | doi=10.1038/235037a0 }}</ref> and [[Charles Thomas Bolton]], working independently at the [[University of Toronto]]'s [[David Dunlap Observatory]],<ref>{{cite journal
| last=Bolton | first=C. T. | year=1972
| title=Identification of Cygnus X-1 with HDE 226868
| journal=Nature | volume=235 | issue=2 | pages=271–273
| url=http://www.nature.com/nature/journal/v235/n5336/abs/235271b0.html
| accessdate=2008-03-10 | doi=10.1038/235271b0 }}</ref> observed [[HDE 226868]] [[wobble]], as if orbiting around an invisible but massive companion. Further analysis led to the declaration that the companion, [[Cygnus X-1]], was in fact a black hole.<ref>{{cite web
| last=Rolston | first=Bruce | date=10 November 1997
| url=http://news.utoronto.ca/bin/bulletin/nov10_97/art4.htm
| title=The First Black Hole | publisher=University of Toronto
| accessdate=2008-03-11 }}
</ref><ref>{{cite journal
| last=Shipman | first=H. L.
| title=The implausible history of triple star models for Cygnus X-1 Evidence for a black hole
| journal=Astrophysical Letters
| year=1975 | volume=16 | issue=1 | pages=9–12
| url=http://adsabs.harvard.edu/abs/1975ApL....16....9S
| accessdate=2008-03-11 }}</ref>
==Alternative models==
{{Main|Nonsingular black hole models}}
Several alternative models, which behave like a black hole but avoid the singularity, have been proposed. However, most researchers judge these concepts artificial, as they are more complicated but do not give near term observable differences from black holes (see [[Occam's razor]]). The most prominent alternative theory is the [[Gravastar]].
In March 2005, physicist [[George Chapline]] at the [[Lawrence Livermore National Laboratory]] in [[California]] proposed that black holes do not exist, and that objects currently thought to be black holes are actually [[dark-energy star]]s. He draws this conclusion from some quantum mechanical analyses. Although his proposal currently has little support in the physics community, it was widely reported by the media.<ref name = "Nature-20050503">
{{cite web| url=http://www.nature.com/news/2005/050328/full/050328-8.html
| title=Black holes 'do not exist'
| publisher=News@Nature.com
| accessdate=2006-03-25}}</ref><ref name = "Arxiv.org-DarkEnergyStars">
{{cite web| url=http://arxiv.org/abs/astro-ph/0503200
| title=Dark Energy Stars
| first=G. | last=Chapline
| accessdate=2006-03-25}}</ref> A similar theory about the non-existence of black holes was later developed by a group of physicists at [[Case Western Reserve University]] in June 2007.<ref>
{{cite web| url=http://blog.case.edu/case-news/2007/06/20/blackholes
| title=Black holes don't exist, Case physicists report
| first =Heidi | last=Cool
| date=2007-06-20
| accessdate=2007-07-02
| publisher=[[Case Western Reserve University]]}}</ref>
Among the alternate models are [[magnetospheric eternally collapsing objects]], clusters of [[elementary particle]]s<ref name="Maoz 1998">
{{cite journal| url=http://www.journals.uchicago.edu/doi/full/10.1086/311194
| journal=The Astrophysical Journal Letters
| volume=494 | issue=2 | pages=L181–L184
| year=1998| month=20 February
| title=Dynamical Constraints On Alternatives To Supermassive Black Holes In Galactic Nuclei
| first=Eyal| last=Maoz
| doi=10.1086/311194}}
</ref> (e.g., [[boson star]]s<ref name = "arxiv.org-Torres2000">
{{cite web| url=http://arxiv.org/abs/astro-ph/0004064
| year=2000
| title=A supermassive boson star at the galactic center?
| first=Diego F.| last=Torres
| coauthors=S. Capozziello, G. Lambiase
| accessdate=2006-03-25}}
</ref>), [[fermion ball]]s,<ref name = "arxiv.org-Munyanezr2001">
{{cite web| url=http://arxiv.org/abs/astro-ph/0103466
| title=The motion of stars near the Galactic center: A comparison of the black hole and fermion ball scenarios
| first=F.| last=Munyaneza
| coauthors=R.D. Viollier
| year=2001
| accessdate=2006-03-25}}
</ref> self-gravitating, degenerate heavy [[neutrino]]s<ref name = "arxiv.org-Tsiklauri1998">
{{cite web| url=http://arxiv.org/abs/astro-ph/9805273
| title=Dark matter concentration in the galactic center
| first=David| last=Tsiklauri
| coauthors=Raoul D. Viollier
| year=1998
| accessdate=2006-03-25}}
</ref> and even clusters of very low mass (~0.04 solar mass) black holes.<ref name="Maoz 1998"/>
==More advanced topics==
===Entropy and Hawking radiation===
In 1971, [[Stephen Hawking]] showed that the total area of the event horizons of any collection of classical black holes can never decrease, even if they collide and swallow each other; that is merge.<ref>[[Stephen Hawking]] ''[[A Brief History of Time]]'', 1998, ISBN 0-553-38016-8</ref> This is remarkably similar to the Second Law of [[Thermodynamics]], with area playing the role of [[entropy]]. As a classical object with zero temperature it was assumed that black holes had zero entropy; if so the second law of thermodynamics would be violated by an entropy-laden material entering the black hole, resulting in a decrease of the total entropy of the universe. Therefore, [[Jacob Bekenstein]] proposed that a black hole should have an entropy, and that it should be proportional to its horizon area. Since black holes do not classically emit radiation, the thermodynamic viewpoint seemed simply an analogy, since zero temperature implies infinite changes in entropy with any addition of heat, which implies infinite entropy. However, in 1974, Hawking applied [[quantum field theory]] to the curved spacetime around the event horizon and discovered that black holes emit [[Hawking radiation]], a form of [[thermal radiation]], allied to the [[Unruh effect]], which implied they had a positive temperature. This strengthened the analogy being drawn between black hole dynamics and thermodynamics: using the [[Laws of black hole mechanics#The First Law|first law of black hole mechanics]], it follows that the entropy of a non-rotating black hole is one quarter of the area of the horizon. This is a universal result and can be extended to apply to cosmological horizons such as in [[de Sitter space]]. It was later suggested that black holes are maximum-entropy objects, meaning that the maximum possible entropy of a region of space is the entropy of the largest black hole that can fit into it. This led to the [[holographic principle]].
The Hawking radiation reflects a characteristic [[temperature]] of the black hole, which can be calculated from its entropy. The more its temperature falls, the more massive a black hole becomes: the more energy a black hole absorbs, the colder it gets. A black hole with roughly the [[Orders of magnitude (mass)#23|mass of the planet Mercury]] would have a temperature in equilibrium with the [[cosmic microwave background]] radiation (about 2.73 K). More massive than this, a black hole will be colder than the background radiation, and it will gain energy from the background faster than it gives energy up through Hawking radiation, becoming even colder still. However, for a less massive black hole the effect implies that the mass of the black hole will slowly evaporate with time, with the black hole becoming hotter and hotter as it does so. Although these effects are negligible for black holes massive enough to have been formed astronomically, they would rapidly become significant for hypothetical [[micro black hole|smaller black holes]], where quantum-mechanical effects dominate. Indeed, small black holes are predicted to undergo runaway evaporation and eventually vanish in a burst of radiation.
[[Image:First Gold Beam-Beam Collision Events at RHIC at 100 100 GeV c per beam recorded by STAR.jpg|thumb|right|400px|If ultra-high-energy collisions of particles in a [[particle accelerator]] can create microscopic black holes, it is expected that all types of particles will be emitted by black hole evaporation, providing key evidence for any [[grand unified theory]]. Above are the high energy particles produced in a gold ion collision on the [[Relativistic Heavy Ion Collider|RHIC]].]]
Although general relativity can be used to perform a semi-classical calculation of black hole entropy, this situation is theoretically unsatisfying. In [[statistical mechanics]], entropy is understood as counting the number of microscopic configurations of a system which have the same macroscopic qualities(such as [[mass]], [[Charge (physics)|charge]], [[pressure]], etc.). But without a satisfactory theory of [[quantum gravity]], one cannot perform such a computation for black holes. Some promise has been shown by [[string theory]], however. There one posits that the microscopic degrees of freedom of the black hole are [[D-brane]]s. By counting the states of D-branes with given charges and energy, the entropy for certain [[supersymmetric]] black holes has been reproduced. Extending the region of validity of these calculations is an ongoing area of research.
===Black hole unitarity===
An open question in fundamental physics is the so-called information loss paradox, or [[black hole information paradox|black hole unitarity]] paradox. Classically, the laws of physics are the same run forward or in reverse. That is, if the position and velocity of every particle in the universe were measured, we could (disregarding [[chaos theory|chaos]]) work backwards to discover the history of the universe arbitrarily far in the past. In quantum mechanics, this corresponds to a vital property called [[unitarity]], which has to do with the conservation of probability.<ref name="PlayDice000">{{cite web
| title = ''Does God Play Dice?'' Archived Lecture by Professor Steven Hawking, Department of Applied Mathematics and Theoretical Physics (DAMTP) University of Caimbridge
| url = http://www.hawking.org.uk/lectures/dice.html
| accessdate = 2007-09-07
}}</ref>
Black holes, however, might violate this rule. The position under classical general relativity is subtle but straightforward: because of the classical [[no hair theorem]], we can never determine what went into the black hole. However, as seen from the outside, information is never actually destroyed, as matter falling into the black hole takes an infinite time to reach the event horizon.
[[Bekenstein bound|Ideas about quantum gravity]], on the other hand, suggest that there can only be a limited finite entropy (i.e. a maximum finite amount of information) associated with the space near the horizon; but the change in the entropy of the horizon plus the entropy of the Hawking radiation is always sufficient to take up all of the entropy of matter and energy falling into the black hole.
Many physicists are concerned however that this is still not sufficiently well understood. In particular, at a quantum level, is the quantum state of the Hawking radiation uniquely determined by the history of what has fallen into the black hole; and is the history of what has fallen into the black hole uniquely determined by the quantum state of the black hole and the radiation? This is what determinism, and unitarity, would require.
For a long time [[Stephen Hawking]] had opposed such ideas, holding to his original 1975 position that the Hawking radiation is entirely thermal and therefore entirely random, containing none of the information held in material the hole has swallowed in the past; this information he reasoned had been lost. However, on 21 July 2004 he presented a new argument, reversing his previous position.<ref name = "Nature-20040407">{{cite web| url=http://www.nature.com/news/2004/040712/full/040712-12.html| title=Hawking changes his mind about black holes| publisher=News@Nature.com| accessdate=2006-03-25}}</ref> On this new calculation, the entropy (and hence information) associated with the black hole escapes in the Hawking radiation itself. However, making sense of it, even in principle, is difficult until the black hole completes its evaporation. Until then it is impossible to relate in a 1:1 way the information in the Hawking radiation (embodied in its detailed internal correlations) to the initial state of the system. Once the black hole evaporates completely, such identification can be made, and unitarity is preserved.
By the time Hawking completed his calculation, it was already very clear from the AdS/CFT correspondence that black holes decay in a unitary way. This is because the fireballs in gauge theories, which are analogous to Hawking radiation, are unquestionably unitary. Hawking's new calculation has not been evaluated by the specialist scientific community, because the methods he uses are unfamiliar and of dubious consistency; but Hawking himself found it sufficiently convincing to pay out on a [[Thorne-Hawking-Preskill bet|bet]] he had made in 1997 with Caltech physicist [[John Preskill]], to considerable media interest.
<!--==Mathematical theory of non-rotating, uncharged black holes==
{{see|Schwarzschild metric |Deriving the Schwarzschild solution}}
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