On flat Euclidean $R^4$ the Laplace operator has the Green function $G(x,y) = \frac{1}{4\pi^2(x-y)^2}$, i.e.
$$-\Delta G(x,y) = \delta^4(x-y).$$
What would be the corresponding Green function on $R \times S^3$? I'm guessing this must be simple because $R \times S^3$ is probably conformally equivalent to $R^4$ (just like $S^4$ is) but not sure how to do the conformal transformation on $G(x,y)$.
