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| '''Micro black holes''', also called '''quantum mechanical black holes''' or '''mini black holes''', are hypothetical tiny [[black holes]], for which [[quantum mechanics|quantum mechanical]] effects play an important role.<ref name="carr">B.J. Carr and S.B. Giddings, "Quantum black holes",[http://www.sciam.com/article.cfm?id=quantum-black-holes Scientific American 292N5 (2005) 30.]</ref> | | Jerrie is what you could certainly call me but Which i don't like when visitors use my full determine. The job I've been [http://www.britannica.com/search?query=occupying occupying] for years is a real people [http://www.wikipedia.org/wiki/manager manager]. Guam is even I've always been enjoying. What I truly doing is fish preserving and I'll be building something else along with it. Go to the little website to find out more: http://circuspartypanama.com<br><br> |
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| It is possible that such quantum [[primordial black holes]] were created in the high-density environment of the early Universe (or [[big bang]]), or possibly through subsequent phase transitions. They might be observed by astrophysicists in the near future, through the particles they are expected to emit by [[Hawking radiation]].
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| Some hypotheses involving additional space dimensions predict that micro black holes could be formed at an energy as low as the [[TeV]] range, which are available in particle accelerators such as the LHC ([[Large Hadron Collider]]). Popular concerns have then been raised over end-of-the-world scenarios (see [[Safety of particle collisions at the Large Hadron Collider]]). However, such quantum black holes would instantly evaporate, either totally or leaving only a very weakly interacting residue. Beside the theoretical arguments, we can notice that the [[cosmic rays]] bombarding the Earth do not produce any damage, although they reach [[center of mass]] energies in the range of hundreds of [[Electronvolt|TeV]].
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| == Minimum mass of a black hole ==
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| In principle, a black hole can have any mass equal to or above the [[Planck mass]] (about 22 micrograms).
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| To make a black hole, one must concentrate mass or energy sufficiently that the [[escape velocity]] from the region in which it is concentrated exceeds the speed of light. This condition gives the [[Schwarzschild radius]], <math>R = 2GM/c^2</math>, where ''G'' is Gravitational constant and ''c'' is the speed of light, of a black hole of mass ''M''. On the other hand, the [[Compton wavelength]], <math>\lambda = h/Mc </math>, where ''h'' is [[Planck constant|Planck's constant]], represents a limit on the minimum size of the region in which a mass ''M'' at rest can be localized. For sufficiently small ''M'', the reduced Compton wavelength (<math>\scriptstyle{\lambda \; = \; \hbar/Mc} </math>, where ''ħ'' is [[Planck constant|Reduced planck constant]]) exceeds half the Schwarzschild radius, and no black hole description exists. This smallest mass for a black hole is thus approximately the [[Planck mass]].
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| Some extensions of present physics posit the existence of extra dimensions of space. In higher-dimensional spacetime, the strength of gravity increases more rapidly with decreasing distance than in three dimensions. With certain special configurations of the extra dimensions, this effect can lower the Planck scale to the TeV range. Examples of such extensions include [[large extra dimension]]s, special cases of the [[Randall-Sundrum model]], and [[string theory]] configurations like the GKP solutions. In such scenarios, black hole production could possibly be an important and observable effect at the [[Large hadron collider|LHC]].<ref name="carr" /><ref name="giddings" /><ref name="dimopoulos" /><ref name="NYT" /><ref name="courier" />
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| It would also be a common natural phenomenon induced by the [[cosmic rays]].
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| All this assumes that the theory of [[general relativity]] remains valid at these small distances. If it does not, then other, presently unknown, effects will limit the minimum size of a black hole.
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| == Stability of a micro black hole ==
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| === Hawking radiation ===
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| {{Main|Hawking radiation}}
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| In 1974 [[Stephen Hawking]] argued that due to [[quantum]] effects,
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| black holes "evaporate" by a process now referred to as [[Hawking radiation]] in which elementary particles (photons, electrons, quarks, gluons, etc.) are emitted.<ref name="hawking">{{cite journal |first=S. W. |last=Hawking |title=Particle Creation by Black Holes |journal=Commun. Math. Phys. |volume=43 |issue=3 |year=1975 |pages=199–220 |doi=10.1007/BF02345020 |bibcode = 1975CMaPh..43..199H }}</ref> His calculations show that the smaller the size of the black hole, the faster the evaporation rate, resulting in a sudden burst of particles as the micro black hole suddenly explodes.
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| Any primordial black hole of sufficiently low mass will [[Hawking evaporation|evaporate]] to near the Planck mass within the lifetime of the Universe. In this process, these small black holes radiate away matter. A rough picture of this is that pairs of [[virtual particle]]s emerge from the [[Vacuum state|vacuum]] near the [[event horizon]], with one member of a pair being captured, and the other escaping the vicinity of the black hole. The net result is the black hole loses mass (due to [[conservation of energy]]). According to the formulae of [[black hole thermodynamics]], the more the black hole loses mass the hotter it becomes, and the faster it evaporates, until it approaches the Planck mass. At this stage a black hole would have a [[Hawking temperature]] of T<sub>P</sub> / 8π (5.6×10<sup>32</sup> K), which means an emitted Hawking particle would have an energy comparable to the mass of the black hole. Thus a thermodynamic description breaks down. Such a mini-black hole would also have an entropy of only 4[[π]] [[Nat (information)|nats]], approximately the minimum possible value. At this point then, the object can no longer be described as a classical black hole, and Hawking's calculations also break down.
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| While Hawking radiation is sometimes questioned,<ref>{{cite journal |first=A. D. |last=Helfer |year=2003 |title=Do black holes radiate? |journal=Reports on Progress in Physics |volume=66 |issue=6 |pages=943 |doi=10.1088/0034-4885/66/6/202 |id= |arxiv=gr-qc/0304042|bibcode = 2003RPPh...66..943H }}</ref> [[Leonard Susskind]] summarizes an expert perspective in his recent book:<ref>{{cite book |first=L. |last=Susskind |title=The Black Hole War: My battle with Stephen Hawking to make the world safe for quantum mechanics |location=New York |publisher=Little, Brown |year=2008 |isbn=978-0-316-01640-7 }}</ref> "Every so often, a physics paper will appear claiming that black holes don't evaporate. Such papers quickly disappear into the infinite junk heap of fringe ideas".
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| === Conjectures for the final state ===
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| Conjectures for the final fate of the black hole include total evaporation and production of a Planck mass-sized black hole remnant. It is possible that such Planck-mass black holes, no longer able either to absorb energy gravitationally like a classical black hole because of the quantised gaps between their allowed energy levels, nor to emit Hawking particles for the same reason, may in effect be stable objects. In such case, they would be WIMPs ([[weakly interacting massive particles]]); this could explain [[dark matter]].<ref>J. H. MacGibbon, Nature 329, 308 (1987)</ref>
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| == Primordial black holes ==
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| {{Main|Primordial black hole}}
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| === Formation in the early Universe ===
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| Production of a black hole requires concentration of mass or energy within the corresponding [[Schwarzschild radius]]. It is hypothesized{{by whom|date=May 2012}} that shortly after the [[big bang]] the Universe was dense enough for any given region of space to fit within its own Schwarzschild radius. Even so, at that time the Universe was not able to collapse into a [[Gravitational singularity|singularity]] due to its uniform mass distribution and rapid growth. This, however, does not fully exclude the possibility that black holes of various sizes may have emerged locally. A black hole formed in this way is called a [[primordial black hole]] and is the most widely accepted hypothesis for the possible creation of micro black holes. Computer simulations suggest that the probability of formation of a primordial black hole is inversely proportional to its mass. Thus the most likely outcome would be micro black holes.{{citation needed|date=May 2012}}
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| === Expected observable effects ===
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| Primordial black holes of initial masses around 10<sup>15</sup> grams would be completing their evaporation today; lighter primordial black holes would have already evaporated.<ref name="carr" /> In optimistic circumstances, the [[Fermi Gamma-ray Space Telescope]] satellite, launched in June 2008, might detect experimental evidence for evaporation of nearby black holes by observing gamma ray bursts.<ref>{{cite journal |title=Primordial black holes as a source of extremely high energy cosmic rays |first=A. |last=Barrau |journal=Astroparticle Physics |volume=12 |issue=4 |year=2000 |pages=269–275 |doi=10.1016/S0927-6505(99)00103-6 |arxiv = astro-ph/9907347 |bibcode = 2000APh....12..269B }}</ref><ref>{{cite news |title=Satellite could open door on extra dimension |first=M. |last=McKee |date=30 May 2006 |work=New Scientist |url=http://www.newscientist.com/article/dn9240-satellite-could-open-door-on-extra-dimension.html }}</ref><ref>{{cite web |url=http://fermi.gsfc.nasa.gov/help/tech/minibh.html |title=Fermi Gamma Ray Space Telescope: "Mini" black hole detection |work= |date= }}</ref> It is unlikely that a collision between a microscopic black hole and an object such as a star or a planet would be noticeable. The small radius and high density of the black hole would allow it to pass straight through any object consisting of normal atoms, interacting with only few of its atoms while doing so. It has, however, been suggested that a small black hole (of sufficient mass) passing through the Earth would produce a detectable acoustic or [[Seismology|seismic]] signal.<ref>{{cite journal |first=I. B. |last=Khriplovich |first2=A. A. |last2=Pomeransky |first3=N. |last3=Produit |lastauthoramp=yes |first4=G. Yu. |last4=Ruban |year=2008 |title=Can one detect passage of small black hole through the Earth? |journal=Physical Review D |volume=77 |issue=6 |pages= 064017 |doi=10.1103/PhysRevD.77.064017 |bibcode = 2008PhRvD..77f4017K |arxiv = 0710.3438 }}</ref><ref>{{cite journal |first=I. B. |last=Khriplovich |first2=A. A. |last2=Pomeransky |first3=N. |last3=Produit |lastauthoramp=yes |first4=G. Yu. |last4=Ruban |title=Passage of small black hole through the Earth. Is it detectable? |journal=Pre-Print |volume= 0801|issue= |pages= 4623|doi= |id= |arxiv=0801.4623|bibcode = 2008arXiv0801.4623K |year=2008 }}</ref><ref>{{cite web |url=http://www.universetoday.com/2007/06/20/are-microscopic-black-holes-buzzing-inside-the-earth |last=Cain |first=Fraser |title=Are Microscopic Black Holes Buzzing Inside the Earth? |work=Universe Today |date=20 June 2007 }}</ref><ref group=lower-alpha>The Schwarzschild radius of a 10<sup>15</sup> gram black hole is ~148 fm ({{nowrap|148 x 10<sup>−15</sup> m}}), which is much smaller than an atom but larger than an atomic nucleus.</ref>
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| == Manmade micro black holes ==
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| === Feasibility of production ===
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| In familiar three-dimensional gravity, the minimum energy of a microscopic black hole is 10<sup>19</sup> [[Electronvolt|GeV]], which would have to be condensed into a region on the order of the [[Planck length]]. This is far beyond the limits of any current technology. It is estimated {{Citation needed|date=January 2008}} that to collide two particles to within a distance of a Planck length with currently achievable magnetic field strengths would require a ring accelerator about 1000 [[light year]]s in diameter to keep the particles on track. [[Stephen Hawking]] also said in chapter 6 of his ''[[Brief History of Time]]'' that physicist [[John Archibald Wheeler]] once calculated that a very powerful hydrogen bomb using all the [[deuterium]] in all the water on Earth could also generate such a black hole, but Hawking does not provide this calculation or any reference to it to support this assertion.
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| However, in some scenarios involving extra dimensions of space, the Planck mass can be as low as the [[Electronvolt|TeV]] range. The [[Large Hadron Collider]] (LHC) has a design energy of 14 TeV for [[proton]]-proton collisions and 1150 TeV for [[Lead|Pb]]-Pb collisions. It was argued in 2001 that in these circumstances black hole production could be an important and observable effect at the LHC<ref name="giddings">{{cite journal |first=S. B. |last=Giddings |lastauthoramp=yes |first2=S. D. |last2=Thomas |year=2002 |title=High-energy colliders as black hole factories: The End of short distance physics |journal=Phys. Rev. D |volume=65 |issue=5 |pages=056010 |doi=10.1103/PhysRevD.65.056010 |id= |arxiv=hep-ph/0106219|bibcode = 2002PhRvD..65e6010G }}</ref><ref name="dimopoulos">{{cite journal |last=Dimopoulos |first=S. |last2=Landsberg |first2=G. L. |year=2001 |title=Black Holes at the Large Hadron Collider |journal=Phys. Rev. Lett. |pmid=11690198 |volume=87 |issue=16 |pages=161602 |doi= 10.1103/PhysRevLett.87.161602|id= |arxiv=hep-ph/0106295 |bibcode=2001PhRvL..87p1602D}}</ref><ref name="NYT">{{cite news |url=http://www.nytimes.com/2001/09/11/science/physicists-strive-to-build-a-black-hole.html |title=Physicists Strive to Build A Black Hole |newspaper=The New York Times | first=George |last=Johnson |date=September 11, 2001 |accessdate=2010-05-12 }}</ref><ref name="courier">{{cite web|url=http://cerncourier.com/cws/article/cern/29199 |work=CERN courier |title=The case for mini black holes |date=November 2004 }}</ref><ref>{{cite journal |publisher=American Institute of Physics |journal=Bulletin of Physics News |volume=558 |date=September 26, 2001 |first=Phillip F. |last=Schewe |first2=Ben |last2=Stein |lastauthoramp=yes |first3=James |last3=Riordon |title=?? }}</ref>
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| or future higher-energy colliders. Such quantum black holes should decay emitting sprays of particles that could be seen by detectors at these facilities.<ref name="giddings" /><ref name="dimopoulos" /> A paper by Choptuik and Pretorius, published on March 17, 2010 in ''[[Physical Review Letters]]'', presented a computer-generated proof that micro black holes must form from two colliding particles with sufficient energy, which might be allowable at the energies of the LHC if additional dimensions are present other than the customary four (three space, one time).<ref>{{cite journal |last=Choptuik |first=Matthew W. |lastauthoramp=yes |first2=Frans |last2=Pretorius |year=2010 |title=Ultrarelativistic Particle Collisions |journal=Phys. Rev. Lett. |volume=104 |pmid=20366461 |issue=11 |pages=111101 |doi=10.1103/PhysRevLett.104.111101 |id= |arxiv=0908.1780 |bibcode=2010PhRvL.104k1101C}}</ref><ref>{{cite journal |last=Peng |first=G. X. |last2=Wen |first2=X. J. |last3=Chen |first3=Y. D. |year=2006 |title=New solutions for the color-flavor locked strangelets |journal=Physics Letters B |volume=633 |issue=2–3 |pages=314–318 |doi=10.1016/j.physletb.2005.11.081 |id= |arxiv=hep-ph/0512112|bibcode = 2006PhLB..633..314P }}</ref>
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| === Safety arguments ===
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| {{Main|Safety of high energy particle collision experiments}}
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| Hawking's calculation<ref name="hawking" /> and more general [[quantum mechanics|quantum mechanical]] arguments predict that micro black holes evaporate almost instantaneously.
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| Additional safety arguments beyond those based on Hawking radiation were given in the paper,<ref>S.B. Giddings and M.L. Mangano, "Astrophysical implications of hypothetical stable TeV-scale black holes", [http://arxiv.org/abs/0806.3381 arXiv:0806.3381], [http://link.aps.org/doi/10.1103/PhysRevD.78.035009 Phys. Rev. D78: 035009, 2008]</ref><ref>M.E. Peskin, "The end of the world at the Large Hadron Collider?" [http://physics.aps.org/articles/v1/14 Physics 1, 14 (2008)]</ref> which showed that in hypothetical scenarios with stable black holes that could damage Earth, such black holes would have been produced by [[cosmic rays]] and would have already destroyed known astronomical objects such as the Earth, Sun, neutron stars, or white dwarfs.
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| == Black holes in quantum theories of gravity ==
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| It is possible, in some theories of quantum gravity, to calculate the quantum corrections to ordinary, classical black holes. Contrarily to conventional black holes which are solutions of gravitational field equations of the general theory of relativity, quantum gravity black holes incorporate quantum gravity effects in the vicinity of the origin, where classically a curvature singularity occurs. According to the theory employed to model quantum gravity effects, there are different kinds of quantum gravity black holes, namely loop quantum
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| black holes, non-commutative black holes, asymptotically safe black holes. In these approaches, black holes are singularity free.
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| [[Virtual black hole|Virtual-micro black holes]] (VMBH) have been proposed by [[Stephen Hawking]] in 1995,<ref>{{cite arXiv |last=Hawking |first=Stephen |authorlink= |eprint=hep-th/9510029v1 |title=Virtual Black Holes |class= |year=1995 |version= |accessdate= }}</ref> and by [[Fabio Scardigli]] in 1999 as part of a [[Grand Unified Theory|GUT]] which could be a [[quantum gravity]] candidate.<ref>{{cite arXiv |last=Scardigli |first=Fabio |authorlink= |eprint=hep-th/9904025 |title=Generalized Uncertainty Principle in Quantum Gravity from Micro-Black Hole Gedanken Experiment |class= |year=1999 |version= |accessdate= }}</ref><ref>https://plus.google.com/+JonathanLangdale/posts/RUroe4Lv2iu</ref>
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| == Micro black holes in fiction ==
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| {{Main|Black holes in fiction}}
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| == See also ==
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| * [[Planck particle]]
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| == Notes ==
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| {{notes}}
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| == References ==
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| {{reflist|colwidth=30em}}
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| == Bibliography ==
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| <div class="references-small">
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| * D. Page, [http://prola.aps.org/abstract/PRD/v13/i2/p198_1 Phys. Rev. D13 (1976) 198] : first detailed studies of the evaporation mechanism
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| * B.J. Carr & S.W. Hawking, [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1974MNRAS.168..399C Mon. Not. Roy. Astron. Soc 168 (1974) 399] : links between primordial black holes and the early universe
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| * A. Barrau et al., [http://arxiv.org/abs/astro-ph/0112486 Astron. Astrophys. 388 (2002) 676], [http://arxiv.org/abs/astro-ph/0207395 Astron. Astrophys. 398 (2003) 403], [http://arxiv.org/abs/astro-ph/0505436 Astrophys. J. 630 (2005) 1015] : experimental searches for primordial black holes thanks to the emitted antimatter
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| * A. Barrau & G. Boudoul, [http://arxiv.org/abs/astro-ph/0212225 Review talk given at the International Conference on Theoretical Physics TH2002] : cosmology with primordial black holes
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| * A. Barrau & J. Grain, [http://arxiv.org/abs/hep-ph/0311238 Phys. Lett. B 584 (2004) 114] : searches for new physics (quantum gravity) with primordial black holes
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| * P. Kanti, [http://arxiv.org/abs/hep-ph/0402168 Int. J. Mod. Phys. A19 (2004) 4899] : evaporating black holes and extra-dimensions
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| * D. Ida, K.-y. Oda & S.C.Park, [http://arxiv.org/abs/hep-th/0602188]: determination of black hole's life and extra-dimensions
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| * Sabine Hossenfelder: ''What Black Holes Can Teach Us'', [http://www.arxiv.org/abs/hep-ph/0412265 hep-ph/0412265]
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| * L. Modesto, [http://arxiv.org/abs/gr-qc/0407097 PhysRevD.70.124009]: Disappearance of Black Hole Singularity in Quantum Gravity
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| * P. Nicolini, A. Smailacic, E. Spallucci, [http://arxiv.org/abs/gr-qc/0510112 j.physletb.2005.11.004]: Noncommutative geometry inspired Schwarzschild black hole
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| * A. Bonanno, M. Reuter, [http://arxiv.org/abs/hep-th/0602159 PhysRevD.73.083005]: Spacetime Structure of an Evaporating Black Hole in Quantum Gravity
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| * S. Fujioka et al., [http://www.nature.com/nphys/journal/v5/n11/abs/nphys1402.html Nature Physics 5, 821 – 825 (2009)]: X-ray astronomy in the laboratory with a miniature compact object produced by laser-driven implosion
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| </div>
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| == External links ==
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| * ''[http://arxiv.org/abs/0806.3381 Astrophysical implications of hypothetical stable TeV-scale black holes]''
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| * A. Barrau & J. Grain, [http://www.cerncourier.com/main/article/44/9/22 The Case for mini black holes] : a review of the searches for new physics with micro black holes possibly formed at colliders
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| * [http://www.space.com/scienceastronomy/060626_mystery_monday.html Mini Black Holes Might Reveal 5th Dimension] – Space.com
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| * [http://www.ostina.org/content/view/3547/1077/ Doomsday Machine Large Hadron Collider?] – A scientific essay about energies, dimensions, black holes, and the associated public attention to CERN, by Norbert Frischauf (also available as Podcast)
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| {{black holes}}
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| [[Category:Black holes]]
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| [[Category:Hypothetical astronomical objects]]
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| [[Category:Hypothetical particles]]
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