Primordial black hole

From Wikipedia, the free encyclopedia

A primordial black hole is a hypothetical type of black hole that is formed not by the gravitational collapse of a star but by the extreme density of matter present during the universe's early expansion.

According to the Hot Big Bang Model (see: Standard Model), during the first few moments after the big bang, pressure and temperature were extremely great. Under these conditions, simple fluctuations in the density of matter may have resulted in local regions dense enough to create black holes. Although most regions of high density would be quickly dispersed by the expansion of the universe, a primordial black hole would be stable, persisting to the present.

Contents 1 Possible detection 2 Implications 3 String theory 4 References 5 See also

[edit] Possible detection

One way to detect primordial black holes is by their Hawking radiation. All black holes are believed to emit Hawking radiation at a rate inversely proportional to their mass. Since this emission further decreases their mass, black holes with very small mass would experience runaway evaporation, creating a massive burst of radiation. A regular black hole (of about 3 solar masses) cannot lose all of its mass within the lifetime of the universe (they would take about 10⁶⁰ years to do so). However, since primordial black holes are not formed by stellar core collapse, they may be of any size. It has been calculated that primordial black holes that were created with a mass of about 10¹² kg would have a lifetime about equal to the age of the universe. If these low-mass black holes exist, we should be able to observe some of these explosions today.

[edit] Implications

The evaporation of primordial black holes has been suggested as one possible explanation for gamma ray bursts. This explanation is, however, considered unlikely. Other problems for which primordial black holes have been suggested as a solution include the dark matter problem, the cosmological domain wall problem ^[1] and the cosmological monopole problem. ^[2]

Even if they do not solve these problems, the low number of primordial black holes (they have never been detected) aids cosmologists by putting constraints on the spectrum of density fluctuations in the early universe.

[edit] String theory

General relativity predicts the smallest primordial black holes would have evaporated by now, but if there were a fourth spatial dimension — as predicted by string theory — it would affect how gravity acts on small scales and "slow down the evaporation quite substantially." ^[3] This could mean there are several thousand black holes in our solar system. To test this theory scientists will use the Gamma-ray Large Area Space Telescope (GLAST) to be put in orbit by NASA in 2007. If they observe specific small interference patterns within gamma-ray bursts; it could be the first indirect evidence for primordial black holes and string theory.

[edit] References

1. ^ D. Stojkovic, K. Freese and G. D. Starkman, Holes in the walls: primordial black holes as a solution to the cosmological domain wall problem, Phys. Rev. D 72, 045012 (2005) preprint.
2. ^ D. Stojkovic and K. Freese, A black hole solution to the cosmological monopole problem, Phys. Lett. B 606, 251-257 (2005) preprint.
3. ^ McKee, Maggie. (2006) NewScientistSpace.com – Satellite could open door on extra dimension

• S.W. Hawking, Commun.Math. Phys. 43 (1975) 199 : the article it all began with !
• D. Page, Phys. Rev. D13 (1976) 198 : first detailed studies of the evaporation mechanism
• B.J. Carr & S.W. Hawking, Mon. Not. Roy. Astron. Soc 168 (1974) 399 : links between primordial black holes and the early universe
• A. Barrau et al., Astron. Astrophys. 388 (2002) 676 , Astron. Astrophys. 398 (2003) 403 , Astrophys. J. 630 (2005) 1015 : experimental searches for primordial black holes thanks to the emitted antimatter
• A. Barrau & G. Boudoul, Review talk given at the International Conference on Theoretical Physics TH2002 : cosmology with primordial black holes
• A. Barrau & J. Grain, Phys. Lett. B 584 (2004) 114 : searches for new physics (quantum gravity) with primordial black holes
• P. Kanti, Int. J. Mod. Phys. A19 (2004) 4899 : evaporating black holes and extra-dimensions

[edit] See also

• Black hole, a general survey

Classification by type:

• Schwarzschild, or still, black hole
• Kerr, or spinning, black hole
• Kerr-Newman and Reissner-Nordström, or charged then spinning, black holes

Classification by mass:

• Micro black hole and extra-dimensional black hole
• Primordial black hole, a hypothetical leftover of the Big Bang
• Stellar black hole, which could either be a static black hole or a rotating black hole
• Intermediate-mass black hole
• Supermassive black hole, which could also either be a static black hole or a rotating black hole