QFT: Lagrangian of a field

Asked Jun 23 '23 at 06:17

Active Jun 23 '23 at 06:55

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I just started going through this http://www.damtp.cam.ac.uk/user/tong/qft.html of QFT and I got stuck at the very beginning. The Lagrangian for the field is derived by:

I think that the second step in this derivation is integration by parts, however after trying multiple times I still don't get what I need to get. Could someone explain what I'm doing wrong and provide step-by-step derivation?

edited Jun 23 '23 at 06:55

Qmechanic

201,751

asked Jun 23 '23 at 06:17

Gytis Vejelis

Hi @Gytis Vejelis and welcome to PSE. I think your confusion may lay to the fact that $\delta\partial_{\mu}\phi_a= \partial_{\mu}\delta\phi_a$, no? Have you used that? – schris38 Jun 23 '23 at 06:39
Possible duplicates: https://physics.stackexchange.com/q/252854/2451 and links therein. – Qmechanic Jun 23 '23 at 06:57
Yes! Now it all makes sense, Thank you! – Gytis Vejelis Jun 23 '23 at 07:46

QFT: Lagrangian of a field

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