Name: Sam (email_not_shown)
Date: 12/17/14-11:04:26 PM Z


Hi,

I'm very confused, so any help is appreciated.

When I evaluate
Tr[DiracMatrix[a] DiracMatrix[b] DiracMatrix[c] DiracMatrix[d]]
I get, as expected
4 (g^(a d) g^(b c)-g^(a c) g^(b d)+g^(a b) g^(c d))
Notice that the minus sign is on the term proportional to g^(a c), which has to be true because the other terms are even permutations of each other and thus must be symmetric.

However, upon evaluating
Tr[DiracMatrix[a] DiracMatrix[\[Beta]] DiracMatrix[
   c] DiracMatrix[\[Delta]]]
I get the incorrect answer
4 (g^(a \[Delta]) g^(c \[Beta])-g^(a \[Beta]) g^(c \[Delta])+g^(a c) g^(\[Beta] \[Delta]))
Notice that the minus sign is on the term proportional to g^(a \[Beta]) now, which is not how it should be.

Is this a problem with how Feyncalc understands Greek letters? If so, this is a big problem, since that is my default when I work by hand and that is naturally how I input my gamma matrices, but when I turn slashes into gamma matrices I use the Latin alphabet.

Any help is appreciated,
Thanks,
Sam



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