Name: Frederik Orellana Date: 04/16/03-03:14:56 PM Z

After thinking a bit about it, let me clarify:

GA is a way of quickly inputting Dirac matrices. The arguments of GA
should not be wrapped in LorentzIndex; this will be done automatically.

Thus the correct input is

DiracSimplify[GA[0,0]]

which returns (in StandardForm)

DiracGamma[ExplicitLorentzIndex[0]].DiracGamma[ExplicitLorentzIndex[0]]

as it should.

Again: FeynCalc does not deal with explicit (integer) Lorentz indices,
but if there is a real need for this kind of funtionality and someone is
willing to contribute the code, we will be happy to look at including it
in the distribution.

Frederik

Frederik Orellana wrote:
> FeynCalc does not deal with explicit Lorentz indices. In fact,
> LorentzIndex[0], LorentzIndex[1], … get replaced with
> ExplicitLorentzIndex[0], ExplicitLorentzIndex[1], … immediately.
>
> DiracSimplify[GA[ExplicitLorentzIndex[0],ExplicitLorentzIndex[0]] should
> then not return 4. It should be left unevaluated. This should be fixed.
> I will look at it. Thanks for reporting it.
>
> If you need to work with explicit Lorentz indices, you are more than
> welcome to contribute code to facilitate this.
>
> Cheers, Frederik
>
>
>
> Zhiwei Huang wrote:
>
>> I don’t know how to input a single gamma matrix such as \gamma^0,
>>\gamma^1 and so on. In physics, the square of \gamma^0 satisfies
>>(\gamma^0)^2 = 1. However, if I input “GA[LorentzIndex[0]]”, I find that
>>“DiracSimplify[GA[LorentzIndex[0],LorentzIndex[0]]” is equal to 4, and
>>if I input “GA[0]”, I find that “DiracSimplify[GA[0,0]” is equal to
>>“DiracGamma(0).DiracGamma(0)”, which is not I expect.
>> Why I can not conduct \gammma^0 like \gamma^5? We can see that
>>“DiracSimplify[GA[5, 5]]” is exactly equal to 1! It’s wonderful.
>> I want to find a command for \gamma^0 matrix which works like the
>>\gamma^5 case. But I can not find the way. So I really want to get help
>>from you.
>>
>>
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