- #1

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- 10

## Homework Statement

## Homework Equations

## The Attempt at a Solution

[/B]

I think I understand part b) . The idea is to move the operator that annihilates to the RHS via the commutator relation.

However I can't seem to get part a.

I have:

## [ P^u, P^v]= \int \int \frac{1}{(2\pi)^6} d^3k d^3 k' (a^{\dagger}(k)a(k)a^{\dagger}(k')a(k') k^u k'^v - a^{\dagger}(k')a(k')a^{\dagger}(k)a(k) k'^vk^u)##

And I can't even think of a first move here, and I don't see anyway to include the commutator expression?

Many thanks in advance