Virial identity for the four-dimensional gravitational Hartree equation (source code)

= Virial identity for the four-dimensional gravitational Hartree equation
{c}
{title2=$I''(t)=16E(u)$}

For a finite-variance solution in four dimensions,
$$
I(t)=\int|x|^2|u(t,x)|^2\,dx
$$
satisfies $I''(t)=16E(u)$. The identity uses the degree $-2$ homogeneity of the Newtonian kernel. Negative-energy finite-variance data consequently blow up in finite time by the convexity argument.