Name: Nixom Date: 08/25/09-04:48:42 PM Z
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….