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FeynCalc / feyncalc

Mathematica package for algebraic calculations in elementary particle physics.
https://feyncalc.github.io
GNU General Public License v3.0
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Error in the simplifications of Dirac matrices involving Light Cone perpendicular vectors (in D dimension) #245

Closed maxferrre closed 6 months ago

maxferrre commented 6 months ago

. Your Mathematica version

13.3.1 for Mac OS X ARM (64-bit) (July 24, 2023)

. Your FeynCalc version

10.0.0

.Did you try to reinstall FeynCalc (stable version) using the automatic installer to make sure that you have the latest bugfixes?

No, but I did check with the latest master branch.

.Does your Mathematica initialization file contain statements that might influence the behavior of FeynCalc? Sometimes external packages may modify init.m in unusual ways, causing troubles for other codes.

No.

.Please provide a minimal working example that illustrates the problem and works on a fresh kernel. The example should be provided either by writing the code (as InputForm!) directly in the issue text or by attaching a Mathematica notebook. Please do not post code samples as screenshots, PDF files etc.: Those essentially require us to retype everything by hand, which is annoying and also time consuming. Please explain the difference between the current behavior and the expected behavior.

<< FeynCalc` GSLRD[p] . GALRD[mu] . GSLRD[p] DiracTrick[%]

OutPut (in InputForm) : 2DiracGamma[LightConePerpendicularComponent[Momentum[p, D], Momentum[FCGV["n"], D], Momentum[FCGV["nb"], D]], D]Pair[LightConePerpendicularComponent[ LorentzIndex[mu, D], Momentum[FCGV["n"], D], Momentum[FCGV["nb"], D]], LightConePerpendicularComponent[Momentum[p, D], Momentum[FCGV["n"], D], Momentum[FCGV["nb"], D]]] - DiracGamma[LightConePerpendicularComponent[LorentzIndex[mu, D], Momentum[FCGV["n"], D], Momentum[FCGV["nb"], D]], D]* Pair[Momentum[p, D], Momentum[p, D]]

the second term should involve "Pair[LightConePerpendicularComponent[Momentum[p, D], Momentum[FCGV["n"], D], Momentum[FCGV["nb"], D],LightConePerpendicularComponent[Momentum[p, D], Momentum[FCGV["n"], D], Momentum[FCGV["nb"], D]]" (the scalar product between the perpendicular components of p), not the full scalar product "Pair[Momentum[p, D], Momentum[p, D]]".

NB : This mistake is not there if I work with dimension 4 objects.

Thank you in advance for your time :)

vsht commented 6 months ago

Hi,

many thanks for the bug report. Could you please check if the fix in the dev version covers all your usage cases?

After that I would push that into stable.

maxferrre commented 6 months ago

Hi,

Thank you for the bug fixing, I can confirm that with this fix my different cases are now giving me the expected results.