Date: 10/21/17-07:10:22 AM Z

> I've stumbled upon a frustrating bug in the FeynCalcExternal form of
> D-dimensional Eps expressions. Essentially, the expressions behave
> differently depending on how many of their indices are contracted with
> four vectors (and which indices are contracted!).
> Attached is a short notebook file that illustrates the point
> concisely. Has anyone else run into this?
>
> Thanks,
>
> Alex Williamson
> University of Toronto

With the current stable and development version this works as expected:

ex1 = Table[
IntegerDigits[n, 2, 4] /. {0 -> LorentzIndex, 1 -> Momentum}, {n,
0, 15}]
ex2 = (Eps[#[[1]][mu, D], #[[2]][nu, D], #[[3]][al, D], #[[4]][be,
D]] &) /@ ex1
FCE /@ ex2

giving

{LCD[al, be, mu, nu], LCD[al, mu, nu][be], -LCD[be, mu, nu][al],
LCD[mu, nu][al, be], LCD[al, be, mu][nu], -LCD[al, mu][be, nu],
LCD[be, mu][al, nu], LCD[mu][al, be, nu], -LCD[al, be, nu][mu],
LCD[al, nu][be, mu], -LCD[be, nu][al, mu], -LCD[nu][al, be, mu],
LCD[al, be][mu, nu], LCD[al][be, mu, nu], -LCD[be][al, mu, nu],
LCD[][al, be, mu, nu]}

I'll nevertheless add this example to our testsuite.

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