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advanced_notions:elementary_particles [2018/04/09 10:46] tesmitekle [FAQ] |
advanced_notions:elementary_particles [2018/04/14 10:08] (current) aresmarrero [Abstract] |
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+ | <blockquote>A question not often addressed when discussing the standard model is how one describes physical | ||
+ | particles. Taking the electron as an example, the assumption usually made is that the free Dirac | ||
+ | spinor in the interacting theory, at asymptotic times, can be viewed as an electron since ‘the coupling | ||
+ | switches off’. This would mean that what is being caught in a detector is really a free fermion. The | ||
+ | problem here, of course, is that in QED and QCD the coupling does not switch off, and assuming | ||
+ | it does so generates infrared divergences. As a result, the spinors do not become free even at | ||
+ | asymptotic times [1, 2], nor do they ever become gauge invariant. [...] | ||
+ | |||
+ | The physical picture is of a matter particle | ||
+ | surrounded by a cloud of ‘photons’, neither of which are individually observable, but which together | ||
+ | constitute a gauge invariant, physical particle. This description is nonlocal, which is an immediate | ||
+ | consequence of gauge invariance, but observables calculated with our states are manifestly local and | ||
+ | correctly reproduce classically expected physics. | ||
+ | |||
+ | <cite>[[https://arxiv.org/abs/0907.4071|Stability, creation and annihilation of charges in gauge theories]] by Anton Ilderton, Martin Lavelle, David McMullan</cite> | ||
+ | |||
+ | |||
+ | </blockquote> | ||
+ | |||
+ | ----- | ||
+ | |||
* http://math.ucr.edu/home/baez/qg-spring2003/elementary/ | * http://math.ucr.edu/home/baez/qg-spring2003/elementary/ | ||
* See http://physics.stackexchange.com/questions/33350/particle-as-a-representation-of-the-lorentz-group | * See http://physics.stackexchange.com/questions/33350/particle-as-a-representation-of-the-lorentz-group | ||
* [[http://www.pnas.org/content/99/1/33.full.pdf|A closer look at the elementary fermions]] by Maurice Goldhaber | * [[http://www.pnas.org/content/99/1/33.full.pdf|A closer look at the elementary fermions]] by Maurice Goldhaber | ||
+ | |||
+ | ----- | ||
<blockquote> | <blockquote> |