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FeynCalc 4.2.0
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lag is an unsimplified deceptively complicated lagrangian. With various simplifying operations, many terms cancel:
![lag = i UVector[QuantumField[DiracBar[Particle[Fermion[20]]]]][x] . DiracGamma[LorentzIndex[μ]] . ((1/2 (NM[-(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity], (i IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - (NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]] + NM[IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]])/(8 DecayConstant[PseudoScalar[2]]^2)] + NM[(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity], -(i IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - (NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]] + NM[IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]])/(8 DecayConstant[PseudoScalar[2]]^2)] - 1/2 i NM[-(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity], QuantumField[Particle[AxialVector[0]], LorentzIndex[μ]][x] + QuantumField[Particle[Vector[0]], LorentzIndex[μ]][x], (i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity]] - 1/2 i NM[(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity], -QuantumField[Particle[AxialVector[0]], LorentzIndex[μ]][x] + QuantumField[Particle[Vector[0]], LorentzIndex[μ]][x], -(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity]]) - i UMatrix[UIdentity] QuantumField[Particle[Vector[1]], LorentzIndex[μ]][x]) . UVector[QuantumField[Particle[Fermion[20]]]][x] + UVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[Fermion[20]]]][x]) - UVector[QuantumField[DiracBar[Particle[Fermion[20]]]]][x] . UVector[QuantumField[Particle[Fermion[20]]]][x] ParticleMass[Fermion[20]] + 1/2 (i UVector[QuantumField[DiracBar[Particle[Fermion[20]]]]][x] . DiracGamma[LorentzIndex[μ]] . NM[-(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity], (i IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - (NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]] + NM[IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]])/(8 DecayConstant[PseudoScalar[2]]^2)] . UVector[QuantumField[Particle[Fermion[20]]]][x] - i UVector[QuantumField[DiracBar[Particle[Fermion[20]]]]][x] . DiracGamma[LorentzIndex[μ]] . NM[(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity], -(i IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - (NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]] + NM[IsoDot[IsoVector[QuantumField[PartialD[LorentzIndex[μ]], Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]])/(8 DecayConstant[PseudoScalar[2]]^2)] . UVector[QuantumField[Particle[Fermion[20]]]][x] + 1/2 UVector[QuantumField[DiracBar[Particle[Fermion[20]]]]][x] . DiracGamma[LorentzIndex[μ]] . NM[-(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity], QuantumField[Particle[AxialVector[0]], LorentzIndex[μ]][x] + QuantumField[Particle[Vector[0]], LorentzIndex[μ]][x], (i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity]] . UVector[QuantumField[Particle[Fermion[20]]]][x] - 1/2 UVector[QuantumField[DiracBar[Particle[Fermion[20]]]]][x] . DiracGamma[LorentzIndex[μ]] . NM[(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity], -QuantumField[Particle[AxialVector[0]], LorentzIndex[μ]][x] + QuantumField[Particle[Vector[0]], LorentzIndex[μ]][x], -(i IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]])/(2 DecayConstant[PseudoScalar[2]]) - NM[IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]], IsoDot[IsoVector[QuantumField[Particle[PseudoScalar[2]]]][x], IsoVector[UMatrix[UGenerator[]]]]]/(8 DecayConstant[PseudoScalar[2]]^2) + UMatrix[UIdentity]] . UVector[QuantumField[Particle[Fermion[20]]]][x]) CouplingConstant[HBChPT2[2]]](HTMLFiles/index_8.gif)
![i Overscript[Overscript[N^( ), _], →] . γ^μ . ((1/2 ((-(i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé) '6 ((i ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] + ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2)) + ((i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé) '6 (-(i ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] + ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2)) - 1/2 i ((-(i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé) '6 (A^( ) _ μ + V^( ) _ μ) '6 ((i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé)) - 1/2 i (((i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé) '6 (V^( ) _ μ - A^( ) _ μ) '6 (-(i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé))) - i ÷¬öé γ^( ) _ μ) . Overscript[N^( ), →] + ∂ _ μ(Overscript[N^( ), →])) + 1/2 C^( ) (i Overscript[Overscript[N^( ), _], →] . γ^μ . ((-(i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé) '6 ((i ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] + ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2))) . Overscript[N^( ), →] - i Overscript[Overscript[N^( ), _], →] . γ^μ . (((i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé) '6 (-(i ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] + ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2))) . Overscript[N^( ), →] + 1/2 Overscript[Overscript[N^( ), _], →] . γ^μ . ((-(i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé) '6 (A^( ) _ μ + V^( ) _ μ) '6 ((i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé)) . Overscript[N^( ), →] - 1/2 Overscript[Overscript[N^( ), _], →] . γ^μ . (((i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé) '6 (V^( ) _ μ - A^( ) _ μ) '6 (-(i Overscript[π^( ), ->] · Overscript[σ, ->])/(2 f _ π^(ó )) - (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->])/(8 (f _ π^(ó ))^2) + ÷¬öé)) . Overscript[N^( ), →]) - Overscript[Overscript[N^( ), _], →] . Overscript[N^( ), →] m _ N^(ó )](HTMLFiles/index_9.gif)
![la = lag // NMExpand // DotSimplify // CommutatorReduce[#, FullReduce -> True] & // Simplify](HTMLFiles/index_10.gif){kind=small}
![1/(128 (f _ π^(ó ))^4) (64 (2 i Overscript[Overscript[N^( ), _], →] . γ^μ . ∂ _ μ(Overscript[N^( ), →]) + C^( ) Overscript[Overscript[N^( ), _], →] . γ^μ . A^( ) _ μ . Overscript[N^( ), →] + Overscript[Overscript[N^( ), _], →] . γ^μ . V^( ) _ μ . Overscript[N^( ), →] + 2 Overscript[Overscript[N^( ), _], →] . γ^μ . γ^( ) _ μ . Overscript[N^( ), →] - 2 Overscript[Overscript[N^( ), _], →] . Overscript[N^( ), →] m _ N^(ó )) (f _ π^(ó ))^4 - 64 C^( ) Overscript[Overscript[N^( ), _], →] . γ^μ . (∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->]) . Overscript[N^( ), →] (f _ π^(ó ))^3 + 16 i (Overscript[Overscript[N^( ), _], →] . γ^μ . (Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->]) . Overscript[N^( ), →] - Overscript[Overscript[N^( ), _], →] . γ^μ . (∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->]) . Overscript[N^( ), →]) (f _ π^(ó ))^2 - 8 C^( ) Overscript[Overscript[N^( ), _], →] . γ^μ . (Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->]) . Overscript[N^( ), →] f _ π^(ó ) + 2 i Overscript[Overscript[N^( ), _], →] . γ^μ . (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->]) . Overscript[N^( ), →] + 2 i Overscript[Overscript[N^( ), _], →] . γ^μ . (Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->]) . Overscript[N^( ), →] + C^( ) Overscript[Overscript[N^( ), _], →] . γ^μ . ((Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->]) A^( ) _ μ) . Overscript[N^( ), →] + Overscript[Overscript[N^( ), _], →] . γ^μ . ((Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->]) V^( ) _ μ) . Overscript[N^( ), →])](HTMLFiles/index_11.gif)
Just to check if DiscardTerms works on complicated expressions, we will apply it to the unsimplified lag.
Say we want just the ππNN part. We have two options:
Either use Method->Coefficient, then we need give only ππ to Retain:
![DiscardTerms[lag, Retain -> {ParticleField[Pion] -> 2}, CommutatorReduce -> True, Method -> Coefficient]](HTMLFiles/index_12.gif){kind=small}
![(i Overscript[Overscript[N^( ), _], →] . γ^μ . (Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->]) . Overscript[N^( ), →])/(8 (f _ π^(ó ))^2) - (i Overscript[Overscript[N^( ), _], →] . γ^μ . (∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->]) . Overscript[N^( ), →])/(8 (f _ π^(ó ))^2)](HTMLFiles/index_13.gif)
or use Method->Expand, then we must give all fields to Retain:
![DiscardTerms[lag, Retain -> {ParticleField[Nucleon] -> 2, ParticleField[Pion] -> 2}, CommutatorReduce -> True, Method -> Expand]](HTMLFiles/index_14.gif){kind=small}
![(i Overscript[Overscript[N^( ), _], →] . γ^μ . (Overscript[π^( ), ->] · Overscript[σ, ->] '6 ∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->]) . Overscript[N^( ), →])/(8 (f _ π^(ó ))^2) - (i Overscript[Overscript[N^( ), _], →] . γ^μ . (∂ _ μ(Overscript[π^( ), ->]) · Overscript[σ, ->] '6 Overscript[π^( ), ->] · Overscript[σ, ->]) . Overscript[N^( ), →])/(8 (f _ π^(ó ))^2)](HTMLFiles/index_15.gif)
Converted by Mathematica (July 10, 2003)