advanced_notions:quantum_field_theory:virtual_particles
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advanced_notions:quantum_field_theory:virtual_particles [2018/04/09 10:44] tesmitekle |
advanced_notions:quantum_field_theory:virtual_particles [2019/02/01 11:58] (current) jakobadmin [Abstract] |
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| Another instance where virtual particles appear is in particle interactions. When two particles, like two electrons collide it can happen that the photon, which is responsible for the interaction, is converted into a electron-positron pair and then back into the photon. These virtual particles must be taken into account in calculations to get the correct results. | Another instance where virtual particles appear is in particle interactions. When two particles, like two electrons collide it can happen that the photon, which is responsible for the interaction, is converted into a electron-positron pair and then back into the photon. These virtual particles must be taken into account in calculations to get the correct results. | ||
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| * http://physics.stackexchange.com/questions/4349/are-w-z-bosons-virtual-or-not/22064#22064 | * http://physics.stackexchange.com/questions/4349/are-w-z-bosons-virtual-or-not/22064#22064 | ||
| * http://www.mat.univie.ac.at/~neum/physfaq/topics/vacfluc | * http://www.mat.univie.ac.at/~neum/physfaq/topics/vacfluc | ||
| + | * https://profmattstrassler.com/articles-and-posts/particle-physics-basics/quantum-fluctuations-and-their-energy/ | ||
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| <tabbox Concrete> | <tabbox Concrete> | ||
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| </blockquote> | </blockquote> | ||
| + | |||
| + | <blockquote>The calculational tool represented by Feynman diagrams suggests an often abused picture | ||
| + | according to which “real particles interact by exchanging virtual particles”. Many | ||
| + | physicists, especially nonexperts, take this picture literally, as something that really and | ||
| + | objectively happens in nature. In fact, I have never seen a popular text on particle physics | ||
| + | in which this picture was not presented as something that really happens. Therefore, this | ||
| + | picture of quantum interactions as processes in which virtual particles exchange is one of | ||
| + | the most abused myths, not only in quantum physics, but in physics in general. Indeed, | ||
| + | there is a consensus among experts for foundations of QFT that such a picture should | ||
| + | not be taken literally. The fundamental principles of quantum theory do not even contain | ||
| + | a notion of a “virtual” state. The notion of a “virtual particle” originates only from a | ||
| + | specific mathematical method of calculation, called perturbative expansion. In fact, perturbative | ||
| + | expansion represented by Feynman diagrams can be introduced even in classical | ||
| + | physics [52, 53], but nobody attempts to verbalize these classical Feynman diagrams in terms of classical “virtual” processes. So why such a verbalization is tolerated in quantum | ||
| + | physics? The main reason is the fact that the standard interpretation of quantum | ||
| + | theory does not offer a clear “canonical” ontological picture of the actual processes in | ||
| + | nature, but only provides the probabilities for the final results of measurement outcomes. | ||
| + | In the absence of such a “canonical” picture, physicists take the liberty to introduce various | ||
| + | auxiliary intuitive pictures that sometimes help them think about otherwise abstract | ||
| + | quantum formalism. Such auxiliary pictures, by themselves, are not a sin. However, a | ||
| + | potential problem occurs when one forgets why such a picture has been introduced in the | ||
| + | first place and starts to think on it too literally. | ||
| + | <cite>Quantum mechanics: Myths and facts by H. Nikolic</cite> | ||
| + | </blockquote> | ||
| <tabbox Abstract> | <tabbox Abstract> | ||
| - | <note tip> | + | <blockquote>"[I]n a closed system all quanta can be considered as virtual." |
| - | The motto in this section is: //the higher the level of abstraction, the better//. | + | <cite>[[https://journals.aps.org/pr/abstract/10.1103/PhysRev.76.769|Richard Feynman]]</cite></blockquote> |
| - | </note> | + | |
| + | * https://www.physicsforums.com/insights/physics-virtual-particles/ | ||
| + | * https://www.physicsforums.com/insights/misconceptions-virtual-particles/ | ||
| <tabbox Why is it interesting?> | <tabbox Why is it interesting?> | ||
| <blockquote>There are no real one-particle systems in nature, not even few-particle | <blockquote>There are no real one-particle systems in nature, not even few-particle | ||
| Line 74: | Line 99: | ||
| -->Do virtual particles actually physically exist?# | -->Do virtual particles actually physically exist?# | ||
| - | see https://physics.stackexchange.com/questions/185110/do-virtual-particles-actually-physically-exist and https://physics.stackexchange.com/questions/109229/virtual-particles-and-physical-laws/109249#109249 | + | see https://physics.stackexchange.com/questions/185110/do-virtual-particles-actually-physically-exist and https://physics.stackexchange.com/questions/109229/virtual-particles-and-physical-laws/109249#109249 and https://physics.stackexchange.com/questions/147096/are-virtual-particles-only-a-fictive-tool-in-equations |
| <-- | <-- | ||
| -->Are vacuum fluctuations really happening all the time? # | -->Are vacuum fluctuations really happening all the time? # | ||
| Line 80: | Line 105: | ||
| see https://physics.stackexchange.com/questions/146003/are-vacuum-fluctuations-really-happening-all-the-time | see https://physics.stackexchange.com/questions/146003/are-vacuum-fluctuations-really-happening-all-the-time | ||
| + | <-- | ||
| + | |||
| + | -->What physical evidence is there that subatomic particles pop in and out of existence?# | ||
| + | see https://physics.stackexchange.com/questions/162845/what-physical-evidence-is-there-that-subatomic-particles-pop-in-and-out-of-exist | ||
| <-- | <-- | ||
| </tabbox> | </tabbox> | ||
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