CSI[i]
can be used as input for 3-dimensional with 3-dimensional Cartesian index i
and is transformed into PauliSigma[CartesianIndex[i]]
by FeynCalcInternal
.
[i] CSI
[i, j] - CSI[j, i] CSI
StandardForm[FCI[CSI[i]]]
(*PauliSigma[CartesianIndex[i]]*)
[i, j, k, l] CSI
StandardForm[CSI[i, j, k, l]]
(*CSI[i] . CSI[j] . CSI[k] . CSI[l]*)