# I Help to understand the Retarded Function

Tags:
1. Nov 26, 2016

### needved

When the Einstein equation are linearized the results are the weak field Einstein equations

$$\left ( -\frac{\partial^{2}}{\partial t^{2}} + \nabla^{2} \right ) \bar h^{\mu\nu}=-16\pi T^{\mu\nu}$$
a solution for this equations considering the source are the Retarded function
$$\bar h^{\mu\nu} (t,\vec x)=4 \int d^{3}x' \frac{[T^{\mu\nu}(t',\vec x')]_{[ret]}}{|\vec x - \vec x'|}$$
with

$$t' = t_{ret} = t-|\vec x - \vec x'|$$

until i know "t" and "x" in spacetime are the same but what physical situation describes
$$|\vec x - \vec x'|$$
Is similar to electromagnestism, when $$\vec x$$ represent the place where you want calculate the potencial and $$\vec x'$$ represent the place where the charge is located?