(ϕ^4) theory

Initialization

Generate model files from phi4.fr by using FeynRules before doing this tutorial. See the example in “phi4_feynrules.wl”.

Quit[];

<<FeynArts`
<<FormCalc`
model=FileNameJoin[{NotebookDirectory[],"phi_to_four_theory_FA","phi_to_four_theory_FA"}];
(*_Hel=0;*)

You can ascertain that the files exist by

FileExistsQ[model<>".mod"]
FileExistsQ[model<>".gen"]

Create Topology (and also ignore helicities)

topo=CreateTopologies[0,2->2];
Paint[topo];
diag=InsertFields[topo,{S[1],S[1]}->{S[1],S[1]},InsertionLevel->{Classes},
Model->model,GenericModel->model]
Paint[diag];

ClearProcess[];
amp=CalcFeynAmp[CreateFeynAmp[diag],FermionChains->VA]
SquaredME[amp]
%[[1]]//.%[[2]]
%//FullForm