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