FAD is the FeynCalc external form of FeynAmpDenominator and denotes an inverse propagator. FAD[q, q-p, ...] is 1/(q^2 (q-p)^2 ...). FAD[{q1,m}, {q1-p,m}, q2, ...] is 1/( (q1^2 - m^2) ( (q1-p)^2 - m^2 ) q2^2 ... ). Translation into FeynCalc internal form is performed by FeynCalcInternal.
See also: FAD, FCE, FCI, FeynAmpDenominator, FeynAmpDenominatorSimplify, PropagatorDenominator.
The FeynCalc Book | Factor2 | FCE |