DiracOrder does not support lightcone components of Dirac matrices and Feynman

[CalunVier]

• Your Mathematica version

14.0.0 for Microsoft Windows (64-bit) (December 13, 2023)

• Your FeynCalc version

10.1.0

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

Yes

• 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.

(** User Mathematica initialization file **)

• 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.

AntiCommutator[GSD[nb], GALRD[\[Nu], n, nb]] = 0
GSD[nb] . GALRD[\[Nu], n, nb] // DiracOrder[#, {\[Nu], nb}] &

output

0
GSD[nb] . GALRD[\[Nu], n, nb]

I was expecting nb and nu to swap places but no.

[vsht]

It works, if you disable DiracTrick.

FCClearScalarProducts[]
ScalarProduct[n] = 0;
ScalarProduct[nb] = 0;
ScalarProduct[n, nb] = 2;
GSD[nb] . GALRD[\[Nu], n, nb] // 
 DiracOrder[#, {\[Nu], nb}, DiracTrick -> False] &

There must be some standard ordering between the LC-components, and the currently chosen one is n,nb,perp. It's hard-coded here

feyncalc/FeynCalc/Dirac/DiracTrick.m

Line 1137 in 52c9848

diracologyDDimFinalOrdering[ b___,DiracGamma[LightConePerpendicularComponent[c_, n_Momentum, nb_Momentum], dim_],