Polarization[k] is the head of a polarization momentum
with momentum k.
A slashed polarization vector (\varepsilon_{\mu}(k) \gamma^\mu) has to be
entered as GS[Polarization[k]].
Unless the option Transversality is set to
True, all polarization vectors are not transverse by
default.
The internal representation for a polarization vector corresponding
to a boson with four momentum k is:
Momentum[Polarization[k, I ]].
Polarization[k,-I] denotes the complex conjugate
polarization.
Polarization is also an option of various functions related to the
operator product expansion. The setting 0 denotes the
unpolarized and 1 the polarized case.
Polarization may appear only inside
Momentum. Outside of Momentum it is
meaningless in FeynCalc.
The imaginary unit in the second argument of
Polarization is used to distinguish between incoming and
outgoing polarization vectors.
Pair[Momentum[k], Momentum[Polarization[k, I]]]
corresponds to \varepsilon^{\mu}(k),
i.e. an ingoing polarization vector
Pair[Momentum[k], Momentum[Polarization[k, -I]]]
corresponds to \varepsilon^{\ast
\mu}(k), i.e. an outgoing polarization vector
Overview, PolarizationVector, PolarizationSum, DoPolarizationSums.
Polarization[k]\text{Polarization}(k)
Polarization[k] // ComplexConjugate\text{Polarization}(k)
GS[Polarization[k]]\bar{\gamma }\cdot \overline{\text{Polarization}(k)}
GS[Polarization[k]] // StandardForm
(*GS[Polarization[k]]*)Pair[Momentum[k], Momentum[Polarization[k, I]]]\overline{k}\cdot \bar{\varepsilon }(k)