Name: Vladyslav Shtabovenko (email_not_shown)
Date: 07/31/15-12:40:34 AM Z


Hi Nikita,

sorry for the late reply. I must also apologize because the FORM code
that I sent you was not correct.

In FORM if one has multiple chains of Dirac matrices, then one has to
specify for each Dirac matrix to which chain it belongs.

<https://www.nikhef.nl/~form/maindir/documentation/tutorial/online/online.html#SECTION00355000000000000000>

In the code I sent all matrices had the same chain number, so that it
was like computing Tr[Line13.Line14+Line15.Line16] opposed to what you
want to compute.

Please the find the corrected code attached. In this case the result is
the same as what you get from FeynCalcFormLink, i.e. the FORM output is
translated to FeynCalc without modifications.

May be you could also check what happens if you compute just
Line13*Line14 or Line15*Line16. You just have to replace

L resFL = TrA2B1 + TrA2B2;

with

L resFL = TrA2B1;

or

L resFL = TrA2B2;

Do those results agree with what you computed by hand?

Cheers,
Vladyslav

Am 28.07.2015 um 23:02 schrieb Nikita Belyaev:
> Hi Vladyslav,
>
>> The attached file is the code for your calculation in FORM. You can run
>> it via
>>
>> form trace.frm
>
> Thank you for that code!
> I've tried to run it and here what I can see. Again considering terms with u^3 I've got the following set of expressions:
>
> - 256*e_[k1,p,p1,s]*p2.k2*u^3 + 256*e_[k1,p,p1,k2]*p2.s*u^3 - 256*e_[k1,p,s,k2]*p1.p2*u^3+
> + 256*e_[k1,p1,p2,s]*p.k2*u^3 - 256*e_[k1,p1,p2,k2]*p.s*u^3 + 512*e_[k1,p1,s,k2]*p.p2*u^3-
> - 256*e_[k1,p2,s,k2]*p.p1*u^3 - 256*e_[p,p1,s,k2]*k1.p2*u^3 + 256*e_[p1,p2,s,k2]*k1.p*u^3
>
> It is very easy to see that by applying the Schouten identity twice we get that this sum is exactly zero as it should be!
>
> Do you have any ideas why FeynCalc have a different output?
>
> Best Regards,
> Nikita Belyaev
>




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