Name: Gang Li (email_not_shown)
Date: 08/03/15-04:26:58 PM Z


Hello, Vladyslav,

I've faced with a problem when I want to extract a particular term using the Mathematica function "Coefficeint".
Num = TR[(GSD[q] + m).(a + I*b*GA5).(GSD[q + pc] + m).(a +
      I*b*GA5).(GSD[q + pa + pb] + m).GAD[mu].(GSD[q + pb] + m).GAD[
     nu]] // Simplify

tmp = Coefficient[Num, a*a] // Simplify
---------------------------------------------
Coefficient[tmp, MTD[mu, nu]] = 0 (does not work!)
_____________________________________________

However,
Coefficient[tmp, Pair[LorentzIndex[mu, D], LorentzIndex[nu, D]]]
works well.

Why does FeynCalc contain different input forms of the same expression?



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