Date: 12/19/16-02:56:23 PM Z

Hi,

in fact, since FeynCalc 9.2 GS[0] does evaluate to 0, i.e.

GS[p] /. p -> 0

gives 0, while GA[0]

evaluates to

DiracGamma[ExplicitLorentzIndex[0]]

Cheers,

>
>
> Hello,
>
> I\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'m working with loop integral involve terms like GS[p], and the moment \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"p\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\" need to be put as zero. But I found something strange:
> _____________________________________
> In[19]:= GS[p] /. p -> 0
>
> Out[19]= \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\[Gamma]\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\[CenterDot]0
> 覧覧覧覧覧覧覧覧
>
> or you can see it more clearly using the StandardForm
> 覧覧覧覧覧覧覧覧
> In[20]:= GS[p] /. p -> 0 // StandardForm
>
> Out[20]//StandardForm= GS[0]
> 覧覧覧覧覧覧覧覧
>
> The result should be zero though. It looks like FeynCalc or Mathematica treat the GS[] as a function but without definition of GS[0] =0.
>
> Furthermore, when the OneLoop involves the GS[0], it will become GA[0]
> ________________________________________
> In[22]:= OneLoop[p, GS[p] /. p -> 0]
>
> Out[22]= \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\[Gamma]^0
> ________________________________________
>
> Similar thing happens on the SPD[k,p], it will be zero when you replace one of the moment to be zero, but
>
> In[30]:= Spinor[k, MT] SPD[k, p] /. p -> 0 //
>
> Out[30]= 0 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\[CurlyPhi](k,MT)
>
> or in StandardForm
> Out[31]= SPD[0, k] Spinor[Momentum[k], MT, 1]
>
> And this \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"0\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\" or SPD[0,k] will become GA[0].GA[0] after applied the OneLoop function in my loop integral.
>
> Could you please look into this case?
> Thank you very much!
>
> Lu Jie

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