What is the source of curvature in an accelerating frame?

[Adel Makram]

I'll respond to this with another question: how can $\nabla^2 \Phi$ be nonzero when $\rho$ is zero, which it is everywhere outside the source? Doesn't that violate Poisson's equation?

(Hint: you might want to check the actual definition of the Laplacian operator $\nabla^2$ in spherical coordinates.)

This is cool, yes it should violate it unless $\nabla^2\Phi$ is zero which it is according to the definition of Lapalacisn operator. Thank you.