FEYN CALC SYMBOL

# DoPolarizationSums sums over vector polarizations for expressions with a factor of the form Pair[LorentzIndex[rho1_], Momentum[Polarization[p_, -I]]]* Pair[LorentzIndex[rho2_], Momentum[Polarization[p_, I]]].

## ExamplesExamplesopen allclose all

### Basic Examples  (1)Basic Examples  (1)

In the following (and indeed everywhere else within FeynCalc), notice that Lorentz indices written as super or subscripts are not to be taken as such. Instead, by convention, when two indices are contracted one is always lower and the other upper.
FeynCalc uses the following normalization of Polarization vectors:
 In:=
 Out= In:=
 Out= DoPolarizationSums is chosen in such a way as to be consistent with this normalization and with  = :
We can choose e.g. the following polarization vectors, labeled with a subscript, { , , , } = {(,0,0,0), (0,,0,0), (0,0,,0), (0,0,0,)}.
 In:=
 In:=
 In:=
 Out= ee[i][μ] is :
 In:=
 In:=
tt[i,j,μ,ν] is  :  = :
 In:=
 Out=   = :
 In:=
 Out= In:=
 Out= In:=
 Out= In:=
 Out= In:=
 Out= In:=
 Out= In:=