SIS
SIS[p]
can be used as input for 3-dimensional σμpμ with 4-dimensional Lorentz vector p and is transformed into PauliSigma[Momentum[p]]
by FeynCalcInternal.
See also
Overview, PauliSigma, SISD.
Examples
σˉ⋅p
SIS[p] // FCI // StandardForm
(*PauliSigma[Momentum[p]]*)
(σˉ⋅p).(σˉ⋅q).(σˉ⋅r).(σˉ⋅s)
SIS[p, q, r, s] // StandardForm
(*SIS[p] . SIS[q] . SIS[r] . SIS[s]*)
SIS[q] . (SIS[p] + m) . SIS[q]
(σˉ⋅q).(σˉ⋅p+m).(σˉ⋅q)