Name: Tomas Brauner (email_not_shown)
Date: 06/21/11-01:31:20 PM Z


I am trying to calculate traces of some complicated matrix expressions dotted with GA[5] and get apparently wrong results. (I can check them by hand.) Originally I suspected Mathematica simply does not understand my input involving scalar as well as matrix products the way I think, but I managed to reduce the problem to this:

expr = GS[a, b, c, d];
expr /. Dot[x_, y__] -> Dot[x, y, GA[5]]

gives the expected result, that is -4ie^{abcd}. However, if I instead try to perform the trace inside the replacement rule:

expr /. Dot[x_, y__] -> Tr[Dot[x, y, GA[5]]]

I get a zero. Where is the problem? I use FeynCalc 8.0.0.beta2 with Mathematica 8.

Tomas Brauner

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