- #1

Arcturus7

- 16

- 0

## Homework Statement

Derive, using the canonical commutation relation of the position space representation of the fields φ(

**x**) and π(

**y**), the corresponding commutation relation in momentum space.

## Homework Equations

[φ(

**x**), π(

**y**)] = iδ

^{3}(

**x**-

**y**)

My Fourier transforms are defined by: $$ φ^*(\vec p)=\int φ(\vec x)e^{-i\vec p⋅\vec x}d^3\vec x $$

## The Attempt at a Solution

I have essentially taken the approach of Fourier transforming my canonical position space commutation relation, but after evaluating: $$[φ^*(\vec p), π^*(\vec q)] =i\int δ^3(\vec x-\vec y)e^{-i(\vec p⋅\vec x+\vec q⋅\vec y)}d^3\vec x d^3\vec y $$ I am left with an integral that I don't know how to solve, namely: $$ i\int e^{-i(\vec p+\vec q)⋅x}d^3\vec x $$

1) Am I right up till here?

and:

2) Any hints on how to solve this integral? I tried using polar coordinates but didn't get very far. I figured there was probably a symmetry I was missing, but I can't for the life of me see what it would be. I know that the answer should be simply $$[φ^*(\vec p), π^*(\vec q)]= i(2π)^3δ^3(\vec p+\vec q) $$