FeynAmpDenominatorSplit[expr]
splits all FeynAmpDenominator[a,b, ...]
in expr
into FeynAmpDenominator[a]*FeynAmpDenominator[b]*...
. FeynAmpDenominatorSplit[expr, Momentum ->q1]
splits all FeynAmpDenominator
in expr into two products, one containing q1
and other momenta, the second being free of q1
.
Overview, FeynAmpDenominatorCombine.
[q1, q1 - p, q1 - q2, q2, q2 - p]
FAD
= FeynAmpDenominatorSplit[%] ex
// FCE // StandardForm
ex
(*FAD[q1] FAD[-p + q1] FAD[q1 - q2] FAD[q2] FAD[-p + q2]*)
= FeynAmpDenominatorSplit[FAD[q1, q1 - p, q1 - q2, q2, q2 - p], Momentum -> {q1}] ex
// FCE // StandardForm
ex
(*FAD[q2, -p + q2] FAD[q1, -p + q1, q1 - q2]*)
[ex] // FCE // StandardForm
FeynAmpDenominatorCombine
(*FAD[q1, q2, q1 - q2, -p + q1, -p + q2]*)