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Bill_K
#3
Feb9-12, 10:02 AM
Sci Advisor
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An interaction term in the Lagrangian which is trilinear leads to a 3-particle vertex, while one which is quadrilinear leads to a 4-particle vertex. These things occur for example in electroweak theory. The kinetic energy term for the W boson is 1/4 WμνWμν where Wμν = ∂μWν - ∂νWμ - gWμ x Wν, which leads among other things to a 4-particle WWWW vertex. Also there is a WWhh vertex from its interaction with the Higgs.