Micro black hole

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A micro black hole, also called a quantum mechanical black hole and inevitably a mini black hole, is simply a tiny black hole for which quantum mechanical effects play an important role. In theory, a black hole can have any size or mass. Under some speculative theories, primordial black holes were created during the big bang at the earliest stages of the evolution of our universe. In 1974 Stephen Hawking theorized that due to quantum effects, such primordial black holes could "evaporate" by a theoretical process now referred to as Hawking Radiation in which particles of matter would be emitted. Under this theory, the smaller the size of the micro black hole, the faster the evaporation rate, resulting in a sudden burst of particles as the micro black hole suddenly explodes. Searches^[1] for such evaporating micro black holes are planned for the GLAST satellite to be launched in 2008, which will search for gamma ray bursts which should be associated with such evaporation.

It is believed that the Large Hadron Collider (LHC) could produce one of these micro black holes. Although the Standard Model of particle physics predicts that LHC energies are far too low to create black holes, some extensions of the Standard Model posit the existence of extra spatial dimensions, in which it would be possible to create micro black holes at the LHC^[2][3][4] at a rate on the order of one per second. According to the standard calculations these are harmless because they would quickly decay by Hawking radiation.

Contents 1 Explanation 1.1 Smallest possible black hole 1.2 Creation of micro black holes 1.3 Stable micro black holes 1.4 Quantum black hole and black hole electron 2 Fireball analogy 3 See also 4 References 5 External links

[edit] Explanation

[edit] Smallest possible black hole

It is believed that the smallest mass a black hole could have is of the order of the Planck mass, which is about 2 × 10⁻⁸ kg or 1.1 × 10¹⁹ GeV/c². At this scale the black hole thermodynamic formulae predict the mini-black hole would have an entropy of only 4π nats; a Hawking temperature of T_P / 8π, requiring thermal energy quanta comparable in energy to almost the mass of the entire mini black hole; and a Compton wavelength equal to the black hole's Schwarzschild radius (this distance being equal to the Planck length). This is the point where a classical gravitational description of the object stops being retrievable with merely small quantum corrections, but in effect completely breaks down.

The existence of a small black hole of this mass is purely hypothetical but if primordial black holes exist, they might reach this condition as the final stage of runaway evaporation due to Hawking radiation. If Hawking Radiation is real, then small black holes would radiate away matter as pairs of virtual quantum particles emerge from the vacuum near the event horizon, with one falling into the black hole, and the other wandering away, with the net result that the black hole loses mass [due to conservation of energy]. Under Hawking's theory, this "evaporation" rate would increase as the black hole lost mass, eventually resulting in a micro black hole that would suddenly explode in a burst of particles.

[edit] Creation of micro black holes

Under standard theories, such an energy to produce a micro black hole is orders of magnitude greater than that which can be produced on Earth in particle accelerators such as the Large Hadron Collider (LHC) (maximum about 1.15 × 10⁶ GeV), or detected in cosmic ray collisions in our atmosphere. It is estimated^{[citation needed]} that to collide two aggregates of fermions to within a distance of a Planck length with the currently achievable magnetic field strength would require a ring accelerator about 1000 light years in diameter to keep the aggregates on track. Even if it were possible, any collision product would be immensely unstable, and almost immediately disintegrate^{[citation needed]}.

Some string theorists have suggested that the multiple dimensions postulated by string theory might make the effective strength of gravity many orders of magnitude stronger at small distances (very high energies). This might effectively lower the Planck energy, and perhaps make black-hole-like descriptions valuable at even lower masses such as those which are reachable at the LHC.^[5][6][7] This higher-dimensional component to gravity is, however, purely theoretical as of 2008.

Steven Hawking also said in chapter 6 of his Brief History of Time that physicist John Wheeler once calculated that a very powerful hydrogen bomb using all the heavy hydrogen 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.

[edit] Stable micro black holes

Others have wondered about the basic assumptions of the quantum gravity program, and whether there is really a compelling case to believe in Hawking radiation^[8]. It is only these quantum assumptions which lead to the crisis at the Planck mass: in classical general relativity, a black hole could in principle be arbitrarily small, once created. Accordingly, it remains a possibility that a stable micro black hole could be created at the LHC, or that they are created in nature by high-energy impacts, only to zip through earth at nearly the speed of light^[9].

[edit] Quantum black hole and black hole electron

Physicist Brian Greene has suggested that the electron may be a micro black hole; see black hole electron. Small black holes would look like elementary particles because they would be completely defined by their mass, charge and spin. On this view, the significance of the Planck mass is that it marks a transition where the Hawking semi-classical approximation breaks down, and a fully quantum mechanical description of the system becomes required. Gravitationally dominated "black hole"-like structures might still exist with these lower masses, but the emission of Hawking radiation would be suppressed by quantum effects, just as an electron constantly orbiting [centripetally accelerating around] an atom does not radiate, despite the apparent predictions of classical electrodynamics.

All that can be said with certainty is that current predictions for the functioning of a black hole with a mass less than Planck mass are inconsistent and incomplete, and it is not known whether a micro black hole can be produced at the energies of the LHC collider or cosmic ray impacts.

[edit] Fireball analogy

The formation of black hole analogs on Earth in particle accelerators has been reported. These black hole analogs, called fireballs, are not the same as gravitational black holes, but they are vital testing grounds for quantum theories of gravity.[35]

They act like black holes because of the correspondence between the theory of the strong nuclear force, which has nothing to do with gravity, and the quantum theory of gravity. They are similar because both are described by string theory. So the formation and disintegration of a fireball in quark gluon plasma can be interpreted in black hole language. The fireball at the Relativistic Heavy Ion Collider [RHIC] is a phenomenon which is closely analogous to a black hole, and many of its physical properties can be correctly predicted using this analogy. The fireball, however, is not a gravitational object. It is presently unknown whether the much more energetic Large Hadron Collider [LHC] would be capable of producing the speculative large extra dimension micro black hole, as many theorists have suggested.

[edit] See also

v • d • e Black holes Formation Stellar evolution · Collapse · Compact star · Tolman-Oppenheimer-Volkoff limit · Primordial black hole Properties Angular momentum · Charge · Size: Micro · Stellar · Intermediate-mass · Supermassive Features Event horizon · Singlarity · Photon sphere · Ergosphere · Hawking radiation Metrics Schwarzschild · Kerr · Reissner-Nordström · Kerr-Newman Issues No hair theorem · Information paradox · Cosmic censorship · Alternative models

[edit] References

[edit] External links

• A. Barrau & J. Grain, The Case for mini black holes : a review of the searches for new physics with micro black holes possibly formed at colliders
• Exit Mundi's micro black hole end of world scenario
• Mini Black Holes Might Reveal 5th Dimension - Space.com