FeynCalc manual (development version)

MomentumExpand

MomentumExpand[expr] expands Momentum[a+b+ ...] in expr into Momentum[a] + Momentum[b] + ....

See also

Overview, ExpandScalarProduct, MomentumCombine.

Examples

MomentumExpand[Momentum[p + q]] // StandardForm

(*Momentum[p] + Momentum[q]*)
ScalarProduct[p + q, r]

(\overline{p}+\overline{q})\cdot \overline{r}

ScalarProduct[p + q, r] // StandardForm

(*Pair[Momentum[p + q], Momentum[r]]*)
ex = MomentumExpand[ScalarProduct[p + q, r]]

(\overline{p}+\overline{q})\cdot \overline{r}

ex // StandardForm

(*Pair[Momentum[p] + Momentum[q], Momentum[r]]*)
ex = MomentumExpand[ScalarProduct[p + q, r - p]]

(\overline{p}+\overline{q})\cdot (\overline{r}-\overline{p})

ex // StandardForm

(*Pair[Momentum[p] + Momentum[q], -Momentum[p] + Momentum[r]]*)