Pair[x, y] is the head of a special pairing used in the internal representation: x and y may have heads LorentzIndex or Momentum. If both x and y have head LorentzIndex, the metric tensor is understood. If x and y have head Momentum, a scalar product is meant. If one of x and y has head LorentzIndex and the other Momentum, a Lorentz vector is understood.
See also: FourVector, FV, FVD, MetricTensor, MT, MTD, ScalarProduct, SP, SPD.
This represents a four-dimensional metric tensor.
This is a D-dimensional metric tensor.
|The FeynCalc Book||OPESumSimplify||PartialD|