Editing Antiparticle (section)

=== Feynman–Stückelberg interpretation <!--'[[Feynman–Stueckelberg interpretation]]', '[[Feynman-Stueckelberg interpretation]]', '[[Stueckelberg–Feynman interpretation]]', '[[Stueckelberg-Feynman interpretation]]', '[[Feynman–Stückelberg interpretation]]', '[[Feynman-Stückelberg interpretation]]', '[[Stückelberg–Feynman interpretation]]', and '[[Stückelberg-Feynman interpretation]]' redirect here-->===

By considering the propagation of the negative energy modes of the electron field backward in time, [[Ernst Stückelberg]] reached a pictorial understanding of the fact that the particle and antiparticle have equal mass '''m''' and spin '''J''' but opposite charges '''q'''. This allowed him to rewrite [[perturbation theory (quantum mechanics)|perturbation theory]] precisely in the form of diagrams. [[Richard Feynman]] later gave an independent systematic derivation of these diagrams from a particle formalism, and they are now called [[Feynman diagram]]s. Each line of a diagram represents a particle propagating either backward or forward in time. In Feynman diagrams, anti-particles are shown traveling backwards in time relative to normal matter, and vice versa.<ref>{{cite book|author=Griffiths, D.J. |author-link=David J. Griffiths |page=61 |year=2008 |title=Introduction to Elementary Particles |edition=2nd |publisher=[[John Wiley & Sons]] |isbn=978-3-527-40601-2|quote=}}</ref> This technique is the most widespread method of computing [[probability amplitude|amplitudes]] in [[quantum field theory]] today.

Since this picture was first developed by Stückelberg,<ref>Stückelberg, Ernst (1941), "La signification du temps propre en mécanique ondulatoire." ''Helv. Phys. Acta'' '''14''', pp. 322–323.</ref> and acquired its modern form in Feynman's work,<ref>{{cite journal|first=Richard P.|last=Feynman|title=Space-time approach to non-relativistic quantum mechanics|journal= [[Reviews of Modern Physics]]|volume= 20|pages= 367–387|year=1948|doi=10.1103/RevModPhys.20.367|bibcode = 1948RvMP...20..367F|issue=2 |url=https://authors.library.caltech.edu/47756/1/FEYrmp48.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://authors.library.caltech.edu/47756/1/FEYrmp48.pdf |archive-date=2022-10-09 |url-status=live}}</ref> it is called the '''Feynman–Stückelberg interpretation'''<!--boldface per WP:R#PLA--> of antiparticles to honor both scientists.