Sigma Matrix

Question

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

Answer 1

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.

Comments

Dear Kasper,

Sorry for the silly question. I was trying to implement some sueprspace calculus and looking in the 1x reference guide I found the sigmamatrix definition. Only afterwards I realised that it remained at the level of definition and no algorithm actually works with it.

Regarding your invitation to ask more questions here, for the moment I do not have any (at least I did not try enough certain things to be able to make up a proper question) as I am at the beginning, but if you know of some note-book making use of superspace claculus (N=1, d=4, a la Wess & Bagger), that may really help. I was looking for some example, but could not find any.

Thanks, Andrei