# Commutation for fields (1 Viewer)

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Hi everyone
in chapter 2 as you know there is a question (2.4) about the commutations between the field and momentum.

[ [P]^{}[j], $$\phi$$ ]

as momentum is in integral form I don't know how to prove them!

I tried to open the terms but I don't know how to put the field in an intergal!

Call the x' integration variable in the definition of P. Calculate the commutator with phi(x) using the fact that integral is linear (much like a sum), therefore commutator with the integral is the integral of commutators. Use what you already know under the integral, simplify.

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