I am trying to use FeynArts -> FeynCalc -> Tarcer to compute some 2-loop self
energy integrals. However, I find that the ToTFI function won't deal with terms in
the numerator which contain an internal loop momentum. I see this when trying to
convert complicated FeynArts output, and I can reproduce the problem with a
simple example, which I copy below.
dm[mu_] := DiracMatrix[mu, Dimension -> 4]
dm := DiracMatrix
ds[p_] := DiracSlash[p]
SetOptions[DiracSlash, Dimension -> 4, FeynCalcInternal -> True];
num := C dm[mu].(ds[k] - M).dm[mu].(ds[k] - ds[q] - M).
dm[nu].(ds[q] - M).dm[nu]
amp := FeynAmpDenominator[PropagatorDenominator[k - p, M],
PropagatorDenominator[k, mw], PropagatorDenominator[k - q, M],
PropagatorDenominator[q, M], PropagatorDenominator[q - p, mw]] //
Contract // FCI
tfiamp := ToTFI[DiracSimplify[num SPC[amp, k, q]], k, q, p]
The output I get is half made up of nice integrals terms like F and V and so on, but
the rest is basically just the original input, for all the terms which contain an internal
momentum (slashed) in the numerator. Is there something I am fundamentally
doing wrong with the input? I am unsure because the ToTFI instructions don't have
an example where there is a dot product of internal momentum and a gamma matrix
like this in the numerator. If I can find the problem in this example then it should
help with also converting the FeynArts output.
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