hi.here is maybe a bug of feyncalc.
firstly i try to calculate Tr[GA[a]GA[b]GA[c]GA[d]],feyncalc gives a correct result 4(g^(ad)g^(bc)-g^(ac)g^(bd)+g^(ab)g^(cd)).
but when i put Tr[GA[a]GA[c]GA[b]GA[d]] (just interchange b and c),feyncalc gives me 4(g^(ad)g^(bc)-g^(ac)g^(bd)+g^(ab)g^(cd)),the same with the above.it should be 4(g^(ad)g^(bc)-g^(ab)g^(cd)+g^(ac)g^(bd)).
i find feyncalc arranges the gamma metrice by their alphabet sequence before it does calculation,so the trace of [abcd] is always 4(g^(ad)g^(bc)-g^(ac)g^(bd)+g^(ab)g^(cd)),no matter abcd,acbd,adbc....
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