# Green function, Delta and Heaviside

1. Feb 19, 2014

### Reingley

1. The problem statement, all variables and given/known data

Show that the explicitly covariant expression:

GR(x-y) = θ(x0-y0)δ(($\vec{x}$-$\vec{y}$)2)/2$\pi$

agrees with the retarded Green function:

δ(x0-y0-|$\vec{x}$-$\vec{y}$|) / (4$\pi$|$\vec{x}$-$\vec{y}$|)

2. Relevant equations

N/A

3. The attempt at a solution

I know that the derivative of the Heaviside function is the delta function, though I'm completely unsure how to apply that to this problem.
My other instinct was to do some Laplace transform, but that seemed futile as well.

Is there some simple property I am missing that would help get me started?