Bug in FeynArts output

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SDrau
Posts: 14
Joined: 21. Feb 2018, 14:54

Bug in FeynArts output

Post by SDrau » 31. Dec 2020, 14:16

Dear developers,

I seem to have stumbled across a bug in FeynArts output. In feynarts.m there is a line setting the gauge parameter for Goldstone bosons:

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WriteString[outputfile,"GaugeXi[S["<>ToString[FeynArtsNr[PART[S][[i,1]]]]<>",1]] = GaugeXi["<>ToString[Select[GoldstoneBosons[InitalizedVertexCalculaton],(FreeQ[#,PART[S][[i,1]]]==False)&][[1,1]]] <>"] /; a > 1 \n"];
At the end of the line

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 /; a>1 
is superfluous since there is no "a" on the left side and should be removed.
Also, the lines that do use "/; a>1" should have the "=" sign replaced with ":=", as the output is otherwise faulty and causes problems.

Having said that, I began wondering whether it is always the case that "/;a>1" ? I think in the model files one can set the Goldstone boson to be any component of some multiplet, so maybe the condition should read "/; a=!= GoldstoneIndex" instead?

Regards,

Simonas

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