FEYN CALC SYMBOL

# FieldDerivative

is the derivative of f[x] with respect to space-time variables x and with Lorentz indices li1, li2, ..., where li1, li2, ... have head LorentzIndex. FieldDerivative[f[x],x,li1,li2,...] can be given as FieldDerivative[f[x],x,{l1,l2,...}], where l1 is li1 without the head, ... 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.