I have a problem in traces evaluation with FeynCalc on Mathematica (<< HighEnergyPhysics`FeynCalc`)
For example in the following
P2 = GS[p2]
P1 = GS[p1]
al = GS[a, pp]
be = GS[pp, a]
DiracTrace[(P2 + m), (al - be), (P1 + m), DiracTraceEvaluate -> True]
gives 0
while if I evaluate separately each piece
DiracTrace[(P2 + m), (al) , (P1 + m), DiracTraceEvaluate -> True]
gives
4(a.pp m^2 + (a.pp)(p1.p2) + (a.p2)(p1.pp) - (a.p1)(p2.pp))
and
DiracTrace[(P2 + m), (-be) , (P1 + m), DiracTraceEvaluate -> True]
gives
4(-(a.pp)m^2 -(a.pp)(p1.p2) + (a.p2)(p1.pp)-(a.p1)(p2.pp))
and so there is a discrepancy between the two results.
I would like to understand where is the mistake.
Thank you in advance
Alessandro Mirizzi
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