FeynCalc manual (development version)

SUNDeltaContract

SUNDeltaContract[exp] substitutes for all SUNDelta in exp SUNDeltaContract, contracts the adjoint SU(N)\text{SU}(N) indices and resubstitutes SUNDelta. SUNDeltaContract[i, j] is the Kronecker-delta for SU(N)\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[%]

(δab)2\left(\delta ^{ab}\right)^2

N21N^2-1