FeynAmp[q, amp] is the head of a Feynman amplitude. amp denotes the analytical expression for the amplitude and q is the integration variable. FeynAmp[q1, q2, amp] denotes a two-loop amplitude.
FeynAmp has no functional properties and serves just as a head. There are however special typesetting rules attached.
See also: Amplitudes.
This is a 1-loop gluon self-energy amplitude (ignoring factors of (2 π)).
This is a generic 2-loop amplitude.
|The FeynCalc Book||FermionSpinSum||FeynAmpDenominator|