# Srednicki 9.25

1. Jul 31, 2010

### kexue

Can anybody help me out with equation 9.25 in Srednicki's QFT book?

He says the in the eq. 9.25 an integration by parts has been carried out. I do not see how. I guess we integrate 9.9 and get then 9.25 somehow, but how? Any hints?

thank you

2. Aug 1, 2010

Anyone?

3. Aug 4, 2010

### Avodyne

Yes, starting with 9.9,
$$-{1\over2}\int d^4x(A\partial^\mu\varphi\partial_\mu\varphi+Bm^2\varphi^2)$$
we partially integrate to move $\partial^\mu$ from the first $\varphi$ to the second, which results in
$$-{1\over2}\int d^4x(-A\varphi\partial^\mu\partial_\mu\varphi+Bm^2\varphi^2)$$
Then we replace fields by functional derivatives in the way that's done throughout section 9.

4. Aug 4, 2010

### kexue

Thanks so much, Avodyne! You are the Srednicki guy, who never lets us down. I rather randomly pick up the book when I'm in the mood to learn some QFT. Well, and as it is, I always quickly stumble upon some equations I don't understand. So thanks so much for the help, because I really want to learn QFT, no matter what!