Name: Nikita Belyaev (email_not_shown)
Date: 08/04/14-11:01:55 AM Z

Thanks for the response, in this particular case it works.
But if I add two gamma matrixes to the formula

Tr1a = Tr[GS[P1].GS[P2].GS[P3].GS[P4].GS[P5].GA[i].(1 - GA[5])];
Tr2a = Tr[GS[Q1].GS[Q2].GS[Q3].GS[Q4].GS[Q5].GA[i].(1 - GA[5])];
Tr3a = Tr[GS[P1].GS[P2].GS[P3].GS[P4].GS[P5].GA[i].GS[Q1].GS[Q2].GS[Q3].GS[Q4].GS[Q5].GA[i].(1 - GA[5])];

Result = Simplify[Contract[Tr1a.Tr2a + 2 Tr3a]] // Schouten

the result is non zero again.

The source of my concern is the following matrix element

Tr1e = Tr[GA[i].(GS[p2] - m).GA[k].(GS[p1] + m)];
Tr2e = Tr[(GS[p] - m).GA[k].(GS[p] + GS[p1] + GS[p2] -
m).GA[l].GS[k2].GA[m].(1 - GA[5])];
Tr3e = Tr[
GS[k1].GA[l].(GS[q] - u).(1 + GA[5].GS[s]).GA[i].(GS[q] -
GS[p1] - GS[p2] - u).GA[m].(1 - GA[5])];
Tr4e = Tr[(GS[p] + GS[p1] + GS[p2] - m).GA[i].(GS[p] -
m).GA[l].GS[k2].GA[m].(1 - GA[5])];
Tr5e = Tr[
GS[k1].GA[l].(GS[q] - GS[p1] - GS[p2] - u).GA[k].(GS[q] -
u).(1 + GA[5].GS[s]).GA[m].(1 - GA[5])];
TrA1A2 = Simplify[Contract[Tr1e.(Tr2e.Tr3e + Tr4e.Tr5e)]] // Schouten

which again contains imaginary part while it should be real.

Is there some rules I have to follow when calculating terms with a lot of gamma matrixes to get a correct result?

Best Regards,
Nikita Belyaev

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