Reducing the functional to a single integral against G #
Q_0 0 is the integral of f_0 squared and the moment term is the double integral of
|u - v| f_0 u f_0 v; added, they are the integral of f_0 against G.
The self-convolution restricted to the support interval.
Part (I): Q₀(0) = ∫_{-1/2}^{1/2} f₀(u)² du.