ExplicitDiracIndex[ind]
is an explicit Dirac index,
i.e., ind
is an integer.
Overview, DiracChain, DCHN, DiracIndex, DiracIndexDelta, DIDelta, DiracChainJoin, DiracChainCombine, DiracChainExpand, DiracChainFactor.
[GA[\[Mu]], 1, 2] DCHN
\left(\bar{\gamma }^{\mu }\right){}_{12}
[GA[\[Mu]], 1, 2] // FCI // StandardForm
DCHN
(*DiracChain[DiracGamma[LorentzIndex[\[Mu]]], ExplicitDiracIndex[1], ExplicitDiracIndex[2]]*)