I try to compute some loop diagram in Mathematica with FeynCalc package.

In the nominator, I have a huge trace and it shows the right solution but in the next step I need to find the solution of a partial derivative such as simply

FieldDerivative[FV[p,Î¼].DiracMatrix[Î½],{FV[p,Î½]}]

and output is

∂pν(pμγν\partial_{p^{\nu}}(p^{\mu}\gamma^{\nu}

But absolutely I expect

γμ\gamma^{\mu}

So do you have any suggestion?

Thanks in advance…

Note: I used “Contract” function but it doesn’t work…

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1 Answer

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If you look at ?FieldDerivative you see that it contains following text

NOTICE: FieldDerivative is defined only for objects with head \

QuantumField[…]. If the space-time derivative of other objects is \

wanted, the corresponding rule must be specified.

I.e. FieldDerivative is used for deriving Feynman rules, but not for differentiating Lorentz tensors. What you need is FourDivergence and this is the code for what you are trying to do:

FourDivergence[FV[p, mu] GA[nu], FV[p, nu]]

which returns what you expect.

P.S. There is a dedicated mailing list for questions related to FeynCalc.