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When I use ComplexConjugate in Feyncalc, if there are repeated indices in its argument, a visual bug occurs. The most minimal example would be:

ComplexConjugate[Contract[GA[\[Mu]].MT[\[Mu], \[Nu]].GA[\[Nu]]]]

for which I get the awful $\gamma^{\$\text{AL(\$30)}}.\gamma^{\$\text{AL(\$30)}}$, or another 'random' number in place of the 30.

The same thing happens without the Contract, but it only occurs with the use of ComplexConjugate.

How can I solve it?

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  • $\begingroup$ Calc @ ComplexConjugate[Contract[GA[[Mu]].MT[[Mu], [Nu]].GA[[Nu]]]] gives 4. $\endgroup$
    – Rolf Mertig
    Commented May 16, 2020 at 22:10
  • $\begingroup$ I don't really know what a "visual bug" is ... . Mathematically it is not a bug. This kind of renaming is necessary for certain more complicated operations in order to avoid getting wrong results. I think I introduced this for calculations involving tensor reductions and Schouten identities. $\endgroup$
    – Rolf Mertig
    Commented May 16, 2020 at 22:15
  • $\begingroup$ Although FeynCalc documentation usually lags behind recent development, this case is actually covered (feyncalc.github.io/FeynCalcBook/ref/ComplexConjugate.html), cf. "Since FeynCalc 9.3 ComplexConjugate will automatically rename dummy indices." $\endgroup$
    – vsht
    Commented May 18, 2020 at 9:40

1 Answer 1

Reset to default
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SetOptions[ComplexConjugate, FCRenameDummyIndices -> False]

will not rename the repeated (dummy) indices.

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  • $\begingroup$ Thank you very much! I'm sorry about calling it a bug, my understanding of these things is less then minimal. Knowing now, from your comment, that this relabeling is useful for some computations I might actually get used to it. $\endgroup$
    – GaloisFan
    Commented May 16, 2020 at 22:40

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