# Sigma Matrix

Hi,

Since SigmaMatrix from the 1.X version is no longer present in Cadabra2, is there a simple way to define this property in a Cadabra2 notebook?

Thanks,
Andrei

That property never really had much use, as none of the algorithms made use of it. In other words, you still had to write out manual substitution rules for sigma products and so on. You can do the same thing in 2.x; just declare \sigma^{m} to be SelfNonCommuting as a starting point, then use substitute to work out sigma products and the like. You may want to look at the ImplicitIndices property documentation to help you convert sigma expressions with and without spinor indices.

We are working on a revamped spinor functionality which will include a lot more in a special package, but it's not yet done and kinda tricky to get right given all the different things people want to do with it.

And as always, feel free to ask here with concrete questions about how to do certain manipulations.