Virtual particle: Difference between revisions

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A '''virtual particle''' is a theoretical transient [[particle]] that exhibits some of the characteristics of an ordinary particle, while having its existence limited by the [[uncertainty principle]], which allows the virtual particles to spontaneously emerge from vacuum at short time and space ranges.<ref>{{cite book |author=Griffiths, D.J. |author-link=David J. Griffiths |page=56 |year=2008 |title=Introduction to Elementary Particles |edition=2nd |publisher=[[John Wiley & Sons]] |year=2008 |isbn=978-3-527-40601-2 |edition=2nd |page=65 |author-link=David J. Griffiths}}</ref> The concept of virtual particles arises in the [[perturbation theory (quantum mechanics)|perturbation theory]] of [[quantum field theory]] (QFT) where interactions between ordinary particles are described in terms of exchanges of virtual particles. A process involving virtual particles can be described by a schematic representation known as a [[Feynman diagram]], in which virtual particles are represented by internal lines.<ref>Peskin, M.E., Schroeder, D.V. (1995). ''An Introduction to Quantum Field Theory'', Westview Press, {{ISBN|0-201-50397-2}}, p. 80.</ref><ref>Mandl, F., Shaw, G. (1984/2002). ''Quantum Field Theory'', John Wiley & Sons, Chichester UK, revised edition, {{ISBN|0-471-94186-7}}, pp. 56, 176.</ref>

Virtual particles do not necessarily carry the same [[mass]] as the corresponding real particle, although they always conserve [[energy]] and [[momentum]]. The closer its characteristics come to those of ordinary particles, the longer the virtual particle exists. They are important in the physics of many processes, including particle scattering and [[Casimir force]]s. In quantum field theory, forces—such as the [[electromagnetic repulsion]] or attraction between two charges—can be thought of as resulting from the exchange of virtual [[photon]]s between the charges. Virtual photons are the [[exchange particle]] for the [[Electromagnetism|electromagnetic interaction]].