Hi all,(adsbygoogle = window.adsbygoogle || []).push({});

I have a question regarding p.97 of Peskin Schroeder and its explantion of disconnected diagram exponentation. I do understand the formula on the buttom of page 96. [tex]\prod{\frac{1}{n_i!}V_{i}^{n_i}} \cdot (value \; of\; connected \; piece)[/tex]

ButI do not understand the sum over [tex] \{ n_i \}[/tex] in the next step!

I would think that I have to sum over the values of all diagrams. Each value is given by the formula which I understand. But why are there two sums?

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# Peskin - exponention of disconnected diagrams

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