- #1

- 35

- 0

## Homework Statement

Show that the radiation field is transverse, ##\vec{\nabla}\cdot\vec{A}=0## and obeys the wave equation ##\nabla^2\vec{A}-\frac{1}{c^2}\partial_t^2\vec{A}=0##. You should start from the expansion of the quantum Electromagnetic field.

## Homework Equations

##H=\frac{1}{2}\int d^3x(E^2+B^2)##

## The Attempt at a Solution

I know that the transverse vector potential gives rise to the EM radiation from moving charges. In this case the Coulomb gauge can be used and both mathematical conditions are met. However, I don't understand what the expansion of the quantum Electromagnetic field or how I could get the answer from it.