Generating one-loop Feynman integrands by multiplying Feynman rules (expressed with FAD, SP, ...) and doing a tensor reduction with TID, generates in some cases the warning
Table::nliter: Non-list iterator PropagatorDenominator(q,0) at position 2 does not evaluate to a real numeric value.
and the obtained result contains artificial symbols FeynAmpDenominator[{FeynCalc`FeynAmpDenominatorSimplify`Private`i, 1, 2}].
Your Mathematica version
12.3.1 for Microsoft Windows (64-bit) (June 24, 2021)
Your FeynCalc version
FeynCalc 10.0.0 (Development version) - Commit d78187b3ab6fcb28d15f2e8d86b67704b4b81940
(version from April 2)
Described problem also happened with FeynCalc 9.3.1 when being run on that version of Mathematica.
Does your Mathematica initialization file contain statements that might influence the behavior of FeynCalc? Sometimes external packages may modify `init.m` in unusual ways, causing troubles for other codes.
Presence of Package-X
Minimal (non-)working example
In[1]:= $KeepLogDivergentScalelessIntegrals = True;
In[2]:= FAD[-p + q] FAD[q, q] FAD[q, q] SP[q, q] // TID[#, q] & // FCE // InputForm
During evaluation of In[2]:= Table::nliter: Non-list iterator PropagatorDenominator(q,0) at position 2 does not evaluate to a real numeric value.
During evaluation of In[2]:= Table::nliter: Non-list iterator PropagatorDenominator(q,0) at position 2 does not evaluate to a real numeric value.
Out[2]//InputForm=
-1/4*(FAD[q, q, -p + q]*FeynAmpDenominator[{FeynCalc`FeynAmpDenominatorSimplify`Private`i, 1, 2}]*(D*SP[p, p] - 4*SPD[p, p]))/(1 - D) +
(FAD[q, -p + q]*FeynAmpDenominator[{FeynCalc`FeynAmpDenominatorSimplify`Private`i, 1, 2}]*(2*SP[p, p] - D*SP[p, p] - 4*SPD[p, p]))/
(2*(1 - D)*SPD[p, p]) + (FAD[q, q]*FeynAmpDenominator[{FeynCalc`FeynAmpDenominatorSimplify`Private`i, 1, 2}]*(D*SP[p, p] - 4*SPD[p, p]))/
(4*(1 - D)*SPD[p, p])
Expected result: the product of FADs get internally combined into a large one, and the obtained result for TID be the same as the following:
In[3]:= FAD[-p + q, q, q, q, q] SP[q, q] // TID[#, q] & // FCE // InputForm
Out[3]//InputForm=
-1/4*(FAD[q, q, q, q, -p + q]*(D*SP[p, p] - 4*SPD[p, p]))/(1 - D) - (FAD[q, q, -p + q]*(D*SP[p, p] - 4*SPD[p, p]))/(4*(1 - D)*SPD[p, p]^2) +
(FAD[q, q, q, -p + q]*(2*SP[p, p] - D*SP[p, p] - 4*SPD[p, p]))/(2*(1 - D)*SPD[p, p])
Description
Generating one-loop Feynman integrands by multiplying Feynman rules (expressed with FAD, SP, ...) and doing a tensor reduction with TID, generates in some cases the warning
Table::nliter: Non-list iterator PropagatorDenominator(q,0) at position 2 does not evaluate to a real numeric value.
and the obtained result contains artificial symbolsFeynAmpDenominator[{FeynCalc`FeynAmpDenominatorSimplify`Private`i, 1, 2}]
.12.3.1 for Microsoft Windows (64-bit) (June 24, 2021)
FeynCalc 10.0.0 (Development version) - Commit d78187b3ab6fcb28d15f2e8d86b67704b4b81940
(version from April 2) Described problem also happened with FeynCalc 9.3.1 when being run on that version of Mathematica.Presence of Package-X
Minimal (non-)working example
Expected result: the product of FADs get internally combined into a large one, and the obtained result for TID be the same as the following: