ThreeDivergence[exp, CV[p, i]] calculates the partial
derivative of exp w.r.t. p^i.
ThreeDivergence[exp, CV[p, i], CV[p,i], ...] gives the
multiple derivative.
Owing to the fact that in FeynCalc dummy Cartesian index are always
understood to be upper indices, applying ThreeDivergence to
an expression is equivalent to the action of \nabla^i = \frac{\partial}{\partial p^i}.
CSP[p, q]
ThreeDivergence[%, CV[q, i]]\overline{p}\cdot \overline{q}
\overline{p}^i
CSP[p - k, q]
ThreeDivergence[%, CV[k, i]](\overline{p}-\overline{k})\cdot \overline{q}
-\overline{q}^i
CFAD[{p, m^2}, p - q]
ThreeDivergence[%, CVD[p, i]]\frac{1}{(p^2+m^2-i \eta ).((p-q)^2-i \eta )}
\frac{2 q^i-2 p^i}{(p^2+m^2-i \eta ).((p-q)^2-i \eta )^2}-\frac{2 p^i}{(p^2+m^2-i \eta )^2.((p-q)^2-i \eta )}
Differentiation of 3-vectors living in different dimensions (3, D-1, D-4) works only in the t’Hooft-Veltman scheme
ThreeDivergence[CVD[p, i], CV[p, j]]
\text{\$Aborted}
FCSetDiracGammaScheme["BMHV"];ThreeDivergence[CVD[p, i], CV[p, j]]\bar{\delta }^{ij}