FCLoopEikonalPropagatorFreeQ[exp] checks if the integral
is free of eikonal propagators \frac{1}{p
\cdot q+x}. If the option First is set to
False, propagators that have both a quadratic and linear
piece, e.g. \frac{1}{p^2 + p \cdot q+x}
will also count as eikonal propagators. The option Momentum
can be used to check for the presence of eikonal propagators only with
respect to particular momenta. The check is performed only for
StandardPropagatorDenominator and
CartesianPropagatorDenominator.
FCI@SFAD[p, p - q]
FCLoopEikonalPropagatorFreeQ[%]\frac{1}{(p^2+i \eta ).((p-q)^2+i \eta )}
\text{True}
FCI@SFAD[{{0, p . q}}]
FCLoopEikonalPropagatorFreeQ[%]\frac{1}{(p\cdot q+i \eta )}
\text{False}
FCI@CFAD[{{0, p . q}}]
FCLoopEikonalPropagatorFreeQ[%, Momentum -> {q}]\frac{1}{(p\cdot q-i \eta )}
\text{False}
FCI@SFAD[{{q, q . p}}]
FCLoopEikonalPropagatorFreeQ[%, First -> False]\frac{1}{(q^2+p\cdot q+i \eta )}
\text{False}