Name: alessandro mirizzi (email_not_shown)
Date: 02/04/05-01:58:38 PM Z


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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