Name: Vladyslav Shtabovenko (email_not_shown)
Date: 11/26/14-10:08:41 PM Z


On the second thought (and after discussing this with Rolf), there is
probably no reason why EpsEvaluate shouldn't expand things like
Momentum[p1+p2-p3] etc. by default. So we decided to add this to the
development version.

Thanks to Lingxiao for bringing this to our attention!

The change is very trivial, so that you can easily "backport" it to
Feyncalc 8.2 or use the workaround with MomentumExpand until the new
version is out.

<https://github.com/FeynCalc/feyncalc/commit/8d58253607842023bf8d1597b71b447ec58bc7ad>

Cheers,
Vladyslav

Am 26.11.2014 um 21:19 schrieb Vladyslav Shtabovenko:
> Hi,
>
> EpsEvaluate doesn't normally expand momenta, but actually it's just one
> additional command that you need:
>
> Eps[Momentum[p1], Momentum[p2], Momentum[p3],
> Momentum[p1 + p2]] // MomentumExpand // EpsEvaluate
>
> Cheers,
> Vladyslav
>
> Am 26.11.2014 um 14:42 schrieb Lingxiao Xu:
>> Hi,
>> Thanks for all the help!
>> So my real problem is how to modify the code which I posted in my
>> first message to prevent all these trivial contractions of LeviCivita
>> tensors from appearing. Since for the process which I want to evaluate,
>> 9 terms would come out. I just don't want to replace the trivial
>> LeviCivita tensors one by one.
>> Furthermore, after checking FeynCalc manual, I think the function
>> EpsEvaluate might help. But it doesn't work correctly. For example,
>> "LC[][p1, p2, p3, p1 + p2] // EpsEvaluate"‍
>> gives" -\[Epsilon]^(p1p2p1+p2p3) " rather
>> than" -\[Epsilon]^(p1p2p1p3)+‍-\[Epsilon]^(p1p2p2p3)".‍‍
>>
>> I am using FeynCalc 8.2.0 with Mathematica 9.0 on Win7(64bits).
>> Thanks for more help.
>>
>> Best Regards!
>> Lingxiao
>>
>



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