Diagrammatic Notation for Tensors: Worthwhile Learning?

[Eidos]

Hi guys

I was first introduced to diagrammatic notation in Roger Penrose's book "Road to Reality".
I wanted to know if any of you are familiar with diagrammatic notation for tensors? As such, is it worthwhile learning? Its certainly a lot clearer (for me anyway :P) than index notation for some of the more complicated structures.

I quite like the way contraction looks and a few of the graphical 'proofs' seem very natural (like the determinant of a product being the product of the determinants).

As an aside: If you were to add two tensors of the same valence, what would the new structure look like?

Thanks
Jacques

 

[shoehorn]

It's junk, in my opinion.