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| title | chunk | source | category | tags | date_saved | instance |
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| Casimir effect | 6/6 | https://en.wikipedia.org/wiki/Casimir_effect | reference | science, encyclopedia | 2026-05-05T10:54:44.616020+00:00 | kb-cron |
== Repulsive forces == There are a few instances where the Casimir effect can give rise to repulsive forces between uncharged objects. Evgeny Lifshitz showed (theoretically) that in certain circumstances (most commonly involving liquids), repulsive forces can arise. This has sparked interest in applications of the Casimir effect toward the development of levitating devices. An experimental demonstration of the Casimir-based repulsion predicted by Lifshitz was carried out by Munday et al. who described it as "quantum levitation". Other scientists have also suggested the use of gain media to achieve a similar levitation effect, though this is controversial because these materials seem to violate fundamental causality constraints and the requirement of thermodynamic equilibrium (Kramers–Kronig relations). Casimir and Casimir–Polder repulsion can in fact occur for sufficiently anisotropic electrical bodies; for a review of the issues involved with repulsion see Milton et al. A notable recent development on repulsive Casimir forces relies on using chiral materials. Q.-D. Jiang at Stockholm University and Nobel Laureate Frank Wilczek at MIT show that chiral "lubricant" can generate repulsive, enhanced, and tunable Casimir interactions. Timothy Boyer showed in his work published in 1968 that a conductor with spherical symmetry will also show this repulsive force, and the result is independent of radius. Further work shows that the repulsive force can be generated with materials of carefully chosen dielectrics.
== Speculative applications == It has been suggested that the Casimir forces have application in nanotechnology, in particular silicon integrated circuit technology based micro- and nanoelectromechanical systems, and so-called Casimir oscillators. In 1995 and 1998 Maclay et al. published the first models of a microelectromechanical system (MEMS) with Casimir forces. While not exploiting the Casimir force for useful work, the papers drew attention from the MEMS community due to the revelation that Casimir effect needs to be considered as a vital factor in the future design of MEMS. In particular, Casimir effect might be the critical factor in the stiction failure of MEMS. In 2001, Capasso et al. showed how the force can be used to control the mechanical motion of a MEMS device. The researchers suspended a polysilicon plate from a torsional rod – a twisting horizontal bar just a few microns in diameter. When they brought a metallized sphere close up to the plate, the attractive Casimir force between the two objects made the plate rotate. They also studied the dynamical behaviour of the MEMS device by making the plate oscillate. The Casimir force reduced the rate of oscillation and led to nonlinear phenomena, such as hysteresis and bistability in the frequency response of the oscillator. According to the team, the system's behaviour agreed well with theoretical calculations. The Casimir effect shows that quantum field theory allows the energy density in very small regions of space to be negative relative to the ordinary vacuum energy, and the energy densities cannot be arbitrarily negative as the theory breaks down at atomic distances. Such prominent physicists such as Stephen Hawking and Kip Thorne, have speculated that such effects might make it possible to stabilize a traversable wormhole.
== See also ==
Negative energy Scharnhorst effect Van der Waals force Squeezed coherent state
== References ==
== Further reading ==
=== Introductory readings === Casimir effect description from University of California, Riverside's version of the Usenet physics FAQ. A. Lambrecht, The Casimir effect: a force from nothing, Physics World, September 2002. NASA Astronomy Picture of the Day: Casimir effect (17 December 2006) Simpson, W. M. R; Leonhardt, U. (2015). Forces of the Quantum Vacuum: An introduction to Casimir physics. World Scientific. ISBN 978-981-4632-90-4.
=== Papers, books and lectures === Casimir, H. B. G.; Polder, D. (1948). "The Influence of Retardation on the London-van der Waals Forces". Physical Review. 73 (4): 360–372. Bibcode:1948PhRv...73..360C. doi:10.1103/PhysRev.73.360. Casimir, H. B. G. (1948). "On the attraction between two perfectly conducting plates" (PDF). Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen. B51: 793–795. Lamoreaux, S. K. (1997). "Demonstration of the Casimir Force in the 0.6 to 6 μm Range". Physical Review Letters. 78 (1): 5–8. Bibcode:1997PhRvL..78....5L. doi:10.1103/PhysRevLett.78.5. S2CID 25323874. Bordag, M.; Mohideen, U.; Mostepanenko, V. M. (October 2001). "New developments in the Casimir effect". Physics Reports. 353 (1–3): 1–205. arXiv:quant-ph/0106045. Bibcode:2001PhR...353....1B. doi:10.1016/S0370-1573(01)00015-1. S2CID 119352552. Milton, K. A. (2001). The Casimir Effect: Physical Manifestations of Zero-point Energy (Reprint ed.). World Scientific. ISBN 978-981-02-4397-5. Dalvit, Diego; Milonni, Peter; Roberts, David; Da Rosa, Felipe (2011). Dalvit, Diego; Milonni, Peter W.; Roberts, David; da Rosa, Felipe (eds.). Casimir Physics. Lecture Notes in Physics. Vol. 834. arXiv:1007.0966. Bibcode:2011LNP...834.....D. doi:10.1007/978-3-642-20288-9. ISBN 978-3-642-20287-2. ISSN 0075-8450. OCLC 844922239. Bressi, G.; Carugno, G.; Onofrio, R.; Ruoso, G. (2002). "Measurement of the Casimir Force between Parallel Metallic Surfaces". Physical Review Letters. 88 (4) 041804. arXiv:quant-ph/0203002. Bibcode:2002PhRvL..88d1804B. doi:10.1103/PhysRevLett.88.041804. PMID 11801108. S2CID 43354557. Kenneth, O.; Klich, I.; Mann, A.; Revzen, M. (2002). "Repulsive Casimir Forces". Physical Review Letters. 89 (3) 033001. arXiv:quant-ph/0202114. Bibcode:2002PhRvL..89c3001K. doi:10.1103/PhysRevLett.89.033001. PMID 12144387. S2CID 20903628. Barrow, J. D. (2005). "Much Ado About Nothing". Lecture at Gresham College. Archived from the original on 30 September 2007. (Includes discussion of French naval analogy.) Barrow, J. D. (2000). The Book of Nothing: Vacuums, Voids, and the Latest Ideas About the Origins of the Universe. Pantheon Books. ISBN 978-0-09-928845-9. (Also includes discussion of French naval analogy.) Downling, J. P. (1989). "The Mathematics of the Casimir Effect". Mathematics Magazine. 62 (5): 324–331. doi:10.1080/0025570X.1989.11977464. Patent No. PCT/RU2011/000847 Author Urmatskih.
=== Temperature dependence === Measurements Recast Usual View of Elusive Force from NIST Nesterenko, V. V.; Lambiase, G.; Scarpetta, G. (2005). "Calculation of the Casimir energy at zero and finite temperature: Some recent results". Rivista del Nuovo Cimento. 27 (6): 1–74. arXiv:hep-th/0503100. Bibcode:2004NCimR..27f...1N. doi:10.1393/ncr/i2005-10002-2. S2CID 14693485.
== External links == Casimir effect article search on arxiv.org G. Lang, The Casimir Force web site, 2002 J. Babb, bibliography on the Casimir Effect web site, 2009 H. Nikolic, The origin of Casimir effect; Vacuum energy or van der Waals force? presentation slides, 2018 Wikiversity:Quantum mechanics/Casimir effect in one dimension