FeynCalc manual (development version)

Momentum

Momentum[p] is the head of a four momentum p.

The internal representation of a 44-dimensional pp is Momentum[p].

For other than 44 dimensions: Momentum[p, dim].

Momentum[p, 4] simplifies to Momentum[p].

See also

Overview, DiracGamma, Eps, LorentzIndex, MomentumExpand.

Examples

This is a 44-dimensional momentum.

Momentum[p]

p\overline{p}

As an optional second argument the dimension must be specified if it is different from 44.

Momentum[p, D]

pp

The dimension index is suppressed in the output.

Momentum[p, d]

pp

Momentum[-q]

q-\overline{q}

Momentum[-q] // StandardForm

(*-Momentum[q]*)
ex = Momentum[p - q] + Momentum[2 q]

(pq)+2q\left(\overline{p}-\overline{q}\right)+2 \overline{q}

ex // StandardForm

(*Momentum[p - q] + 2 Momentum[q]*)
ex // MomentumExpand // StandardForm

(*Momentum[p] + Momentum[q]*)
ex // MomentumCombine // StandardForm

(*Momentum[p + q]*)
ChangeDimension[Momentum[p], d] // StandardForm

(*Momentum[p, d]*)