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|Unsolved problem in physics:
In cosmology, the vacuum catastrophe is the disagreement of over 100 orders of magnitude between measured values of the vacuum energy density and the theoretical zero-point energy suggested by quantum field theory. This discrepancy has been described as "the worst theoretical prediction in the history of physics."
The magnitude of this discrepancy is entirely beyond the descriptive power of any kind of commonplace comparison. For instance, the statement "the observable universe consists of exactly one elementary particle" is closer to being accurate, by at least ten orders of magnitude, than the incorrect vacuum-catastrophe prediction.
It should be stressed that quantum field theory in itself gives no prediction for any measurable vacuum energy unless several assumptions are made that have no grounds in observation or established theory. These include the assumption that quantum field theory acts as a natural and effective field theory down to the Planck scale and the assumption that vacuum energy gravitates. The nature of vacuum energy continues to be of great theoretical interest because of the ambiguities in what our best theories appear to suggest for it.
The problem was identified at an early stage by Walther Nernst, who raised the question of the consequences of such a huge energy of vacuum on gravitational effects. A recent philosophical and historical assessment is provided by Rugh and Zinkernagel.
- MP Hobson, GP Efstathiou & AN Lasenby (2006). General Relativity: An introduction for physicists (Reprint ed.). Cambridge University Press. p. 187. ISBN 978-0-521-82951-9.
- Bianchi, Eugenio; Rovelli, Carlo (2010). "Why all these prejudices against a constant?". arXiv:1002.3966 [astro-ph.CO].
- W Nernst (1916). "Über einen Versuch von quantentheoretischen Betrachtungen zur Annahme stetiger Energieänderungen zurückzukehren". Verhandl. der Deutschen Phys. Gesellschaften (in German) 18: 83.
- TM Nieuwenhuizen (2007). Beyond the quantum. World Scientific. p. 250. ISBN 981-277-117-4.
- SE Rugh, H Zinkernagel; Zinkernagel (2002). "The quantum vacuum and the cosmological constant problem". Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 33 (4): 663–705. doi:10.1016/S1355-2198(02)00033-3.