Name: Vladyslav Shtabovenko (email_not_shown)
Date: 04/08/15-04:49:54 PM Z


The bug if now fixed in the repository

<https://github.com/FeynCalc/feyncalc/commit/1cc6a191ca358e106381851776b6ba433bda791b>

and

a = DiracReduce[DiracMatrix[i].DiracMatrix[j].DiracMatrix[k]];
b = DiracReduce[DiracMatrix[i].DiracMatrix[j].DiracMatrix[k]];
DiracSimplify[(SpinorUBar[p, m].a.SpinorU[p, m]) (SpinorUBar[k,
     m].b.SpinorU[k, m])]

a = DiracMatrix[i].DiracMatrix[j].DiracMatrix[k];
b = DiracMatrix[i].DiracMatrix[j].DiracMatrix[k];
DiracReduce[(SpinorUBar[p, m].a.SpinorU[p, m]) (SpinorUBar[k,
     m].b.SpinorU[k, m

return the same result. Thanks again!

Cheers,
Vladyslav

Am 01.04.2015 um 15:58 schrieb Vladyslav Shtabovenko:
> Hi Asher,
>
> thanks for reporting this. The problem comes from the index renaming
> in DiracReduce, that doesn't take into account that the double index can
> already appear in the expression.
>
> We will fix this in the master repository very soon. For now, you can
> either remove the line
>
> temp = Contract[temp, Rename-> True];
>
> in DiracReduce.m, or, if you are using the development version, apply
> FCRenameDummyIndices on the results of DiracReduce:
>
> a = DiracReduce[DiracMatrix[i].DiracMatrix[j].DiracMatrix[k]] //
> FCRenameDummyIndices;
> b = DiracReduce[DiracMatrix[i].DiracMatrix[j].DiracMatrix[k]] //
> FCRenameDummyIndices;
> DiracSimplify[(SpinorUBar[p, m].a.SpinorU[p, m]) (SpinorUBar[k,
> m].b.SpinorU[k, m])]
>
> Sorry for the inconvenience.
>
> Cheers,
> Vladyslav
>
> Am 31.03.2015 um 00:55 schrieb Asher Berlin:
>> Hi,
>>
>> I've noticed that using DiracReduce on matrices before entering them into expressions involving spinors results in errors in the final evaluation. Consider the following input below:
>>
>> a = DiracReduce[DiracMatrix[i].DiracMatrix[j].DiracMatrix[k]];
>> b = DiracReduce[DiracMatrix[i].DiracMatrix[j].DiracMatrix[k]];
>> DiracSimplify[(SpinorUBar[p, m].a.SpinorU[p, m])(SpinorUBar[k,m].b.SpinorU[k,m])]
>>
>> a = DiracMatrix[i].DiracMatrix[j].DiracMatrix[k];
>> b = DiracMatrix[i].DiracMatrix[j].DiracMatrix[k];
>> DiracReduce[(SpinorUBar[p, m].a.SpinorU[p, m])(SpinorUBar[k,m].b.SpinorU[k,m])]
>>
>> You'll notice that the 2 lines of output differ in one of the terms. I've tried this using FC 8.2 and FC 9 and the same discrepancy remains. Any ideas of what could be going wrong here?
>>



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