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could anyone explain to me why in effective field theory (as in ch29 srednicki), you look at diagrams with only [tex]k<\Lambda[/tex] as external lines and [tex]k>\Lambda[/tex] for your interal lines? why do these diagrams with say, 6 external legs of this type, equate to the constant [tex] c_6 [/tex] say? In previous chapters of the book it's usually the exact 6 point vertex function that would equate to such a diagram, not the 6 point coupling constant itself etc.

I understand the math behind what Srednicki is doing, but not sure I understand what he is actually trying to do here, so all comments on this whole topic in QFT would be great.

thanks

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# Wilsonian effective field theory

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