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Dear Jong-Wan,

the result

I \[Pi]^2 (-((A0[m^2] GA[\[Alpha]])/(2 (1 - D))) +

2 FV[p, \[Alpha]] GS[p] - ((2 - 4 D + D^2) A0[m^2] FV[

p, \[Alpha]] GS[p])/(2 (1 - D) m^2))

is correct. What is (in general) not correct and dangerous, is to do

exp /. D->4

Please have a look at

https://github.com/FeynCalc/feyncalc/wiki/FAQ#limitto4

this should explain it better.

Cheers,

Vladyslav

Am 24.11.2016 um 06:17 schrieb Jong-Wan Lee:

*> Dear Frederik,
*

*>
*

*> I used to use Feyncalc 8.2.0 on Mathematica 9, and recently I started to
*

*> use Feyncalc 9.2.0 on Mathematica 11. However, I encountered a problem
*

*> in doing the one loop integral,
*

*>
*

*> SP[p,p]=m^2;(*kinematics*)
*

*> SetOptions[B0, BReduce->True, B0Unique->True, B0Real->True];
*

*> OneLoop[k, FVD[k, \[Alpha]].GSD[k] FAD[{k, m}, p - k]];
*

*>
*

*> In the old version, I have
*

*>
*

*> I \[Pi]^2 (m^2 DiracGamma[LorentzIndex[\[Alpha]]]+8
*

*> DiracGamma[Momentum[p]] Pair[LorentzIndex[\[Alpha]],
*

*> Momentum[p]] )/9 + (
*

*> I \[Pi]^2 A0[m^2] (m^2 DiracGamma[LorentzIndex[\[Alpha]]] +
*

*> 2 DiracGamma[Momentum[p]] Pair[LorentzIndex[\[Alpha]],
*

*> Momentum[p]]))/(6 m^2)
*

*>
*

*> but, in the new version, I have
*

*>
*

*> 2 I \[Pi]^2 DiracGamma[Momentum[p]] Pair[LorentzIndex[\[Alpha]],
*

*> Momentum[p]] + (
*

*> I \[Pi]^2 A0[m^2] (m^2 DiracGamma[LorentzIndex[\[Alpha]]] +
*

*> 2 DiracGamma[Momentum[p]] Pair[LorentzIndex[\[Alpha]],
*

*> Momentum[p]]))/(6 m^2)
*

*>
*

*> Comparing the two results, I find that the second terms which include
*

*> the UV divergence terms are same, but the first finite terms are
*

*> different. In fact the result from the old version is the correct one.
*

*> Can you help me to resolve this problem?
*

*>
*

*> Best regards,
*

*> Jong-Wan
*

- application/mathematica attachment: example.nb

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