CV[p, i]
is a 3-dimensional Cartesian vector and is
transformed into
CartesianPair[CartesianMomentum[p], CartesianIndex[i]]
by
FeynCalcInternal
.
Overview, FV, Pair, CartesianPair.
[p, i] CV
\overline{p}^i
[p - q, i] CV
\left(\overline{p}-\overline{q}\right)^i
[CV[p, i]] // StandardForm
FCI
(*CartesianPair[CartesianIndex[i], CartesianMomentum[p]]*)
ExpandScalarProduct
is used to expand momenta in
CV
[CV[p - q, i]] ExpandScalarProduct
\overline{p}^i-\overline{q}^i