FeynCalc manual (development version)

SI

SI[mu] can be used as input for 3-dimensional \sigma^{\mu } with 4-dimensional Lorentz index \mu and is transformed into PauliSigma[LorentzIndex[mu]] by FeynCalcInternal.

See also

Overview, PauliSigma, SID, SIE.

Examples

SI[\[Mu]]

\bar{\sigma }^{\mu }

SI[\[Mu]] // FCI // StandardForm

(*PauliSigma[LorentzIndex[\[Mu]]]*)

SI[\[Mu], \[Nu]] - SI[\[Nu], \[Mu]]

\bar{\sigma }^{\mu }.\bar{\sigma }^{\nu }-\bar{\sigma }^{\nu }.\bar{\sigma }^{\mu }

SI[\[Mu], \[Nu], \[Rho], \[Sigma]]

\bar{\sigma }^{\mu }.\bar{\sigma }^{\nu }.\bar{\sigma }^{\rho }.\bar{\sigma }^{\sigma }

SI[\[Mu], \[Nu], \[Rho], \[Sigma]] // StandardForm

(*SI[\[Mu]] . SI[\[Nu]] . SI[\[Rho]] . SI[\[Sigma]]*)

SI[\[Alpha]] . (SIS[p] + m) . SI[\[Beta]]

\bar{\sigma }^{\alpha }.\left(\bar{\sigma }\cdot \overline{p}+m\right).\bar{\sigma }^{\beta }