❓What is the Hessian matrix of the gravitational potential?

The Hessian matrix of a scalar field $\phi(x)$ is the matrix of its second partial derivatives, $H_{i j}=\frac{\partial^2 \phi}{\partial x^3 \partial x^3}$. Therefore, the gravitational tidal tensor is simply minus the Hessian matrix of the gravitational potential: $T_{i j}=-H_{i j}(\phi)$

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