FeynCalc manual (development version)

KD

KD[i, j] is the Kronecker delta in 3 dimensions.

See also

Overview, CartesianPair, KDD.

Examples

KD[i, j]

\bar{\delta }^{ij}

Contract[KD[i, j] KD[i, j]]

3

KD[a, b] // StandardForm

(*KD[a, b]*)
FCI[KD[a, b]] // StandardForm

(*CartesianPair[CartesianIndex[a], CartesianIndex[b]]*)
FCE[FCI[KD[a, b]]] // StandardForm

(*KD[a, b]*)