FeynCalc manual (development version)

SUNDeltaContract

SUNDeltaContract[exp] substitutes for all SUNDelta in exp SUNDeltaContract, contracts the adjoint $\text{SU}(N)$ indices and resubstitutes SUNDelta. SUNDeltaContract[i, j] is the Kronecker-delta for $\text{SU}(N)$ in the adjoint representation with contraction properties. It wraps the head SUNIndex around its arguments.

See also

Overview, SUNDelta, SUNIndex.

Examples

SUNDelta[SUNIndex[a], SUNIndex[b]]^2 
 
SUNDeltaContract[%]

$$\left(\delta ^{ab}\right)^2$$

$$N^2-1$$