Name: Lu Jie (email_not_shown)
Date: 11/05/12-03:41:19 PM Z


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

or you can see it more clearly using the StandardForm
In[20]:= GS[p] /. p -> 0 // StandardForm

Out[20]//StandardForm= GS[0]

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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