## SUNFDeltaContract

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

### See also

[Overview](Extra/FeynCalc.md), [SUNFDelta](SUNFDelta.md), [SUNFIndex](SUNFIndex.md).

### Examples

```mathematica
SUNFDelta[SUNFIndex[a], SUNFIndex[b]]^2 
 
SUNFDeltaContract[%]
```

$$\delta _{ab}^2$$

$$N$$