FourLaplacian[exp, p, q] is ∂∂pμ∂∂qμ\frac{\partial}{\partial p_{\mu }} \frac{\partial}{\partial q_{\mu }}∂pμ∂∂qμ∂ applied to exp.
FourLaplacian[exp, p, q]
exp
Overview, FourDivergence, ThreeDivergence.
SP[q, q] FourLaplacian[%, q, q]
q‾2\overline{q}^2q2
2D2 D2D
SOD[q]^OPEmFAD[q, q - p] FourLaplacian[%, q, q]
(Δ⋅q)OPEmFAD(q,q−p)(\Delta \cdot q)^{\text{OPEmFAD}(q,q-p)}(Δ⋅q)OPEmFAD(q,q−p)
000