· FeynCalc

Name: Vladyslav Shtabovenko Date: 11/24/15-12:32:15 PM Z

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In reply to: Manuel J. Vicente: “FermionSpinSum”

Hi,

thanks for the bug report. This is should be now fixed.

https://github.com/FeynCalc/feyncalc/commit/56d5ca027116332ec88b73855ad54ffce9cdbd86

Cheers,
Vladyslav

Am 23.11.2015 um 16:27 schrieb Manuel J.Vicente:
> Hi,
> using F9.0.0 I get an strange result from FermionSpinSum:
>
> part1 = Spinor[pp, m].(GA[mu] f1 + GA[mu, 5] fa).Spinor[p, m]
> part1cc = ComplexConjugate[part1] /. mu -> nu
> aux=FermionSpinSum[part1cc part1]
> aux/.DiracTrace->Tr
>
>
> 4*f1^2*(Pair[LorentzIndex[mu], Momentum[pp]]*Pair[LorentzIndex[nu], Momentum[p]] +
> Pair[LorentzIndex[mu], Momentum[p]]*Pair[LorentzIndex[nu], Momentum[pp]] +
> Pair[LorentzIndex[mu], LorentzIndex[nu]]*(m^2 - Pair[Momentum[p], Momentum[pp]]))
>
> The result is only a part of the full tensor. In fact, it doesn’t depend on fa at all! The correct result can be recovered just by
>
> Tr[(DiracSlash[p] + m).(GA[nu] f1 - GA[5, nu] fa).(DiracSlash[pp] +
> m).(GA[mu] f1 + GA[mu, 5] fa)]
>
>
> The simpler case with nu=mu also fails.
>
>
> p.s. it works fine in the 8.2 version
>
> best regards
> Manuel J. Vicente
>

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