# Peskin, Schroeder (2.30)

#### Ratzinger

Can someone tell me what the two commutators in (2.30) stand for? It has to be Dirac delta functions, but which one exactly?

thank you

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#### hellfire

Acording to (2.29) the first one should be - $\delta$(p' + p) and the second $\delta$(p + p'). After substracting both the negative sign as well as the factor 2 cancel in (2.30). I guess you should then make use of:

$$\int \delta(p + p^{\prime}) F(p^{\prime}) dp^{\prime} = F(- p)$$

to obtain the final result in (2.30).

#### Ratzinger

Thanks hellfire

"Peskin, Schroeder (2.30)"

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