〈 Berger | Dillon 〉

Thanks for the thread. Interesting to hear that you are sold on this, Predrag.

Sold on it? He practically wrote the book! And the book is here: http://birdtracks.eu/version9.0/GroupTheory.pdf …

I wasn’t talking about bird tracks! I know Predrag wrote the book – I have it, and love it! I was talking about the newly proposed diagrammatic approach to vector calculus (The topic of Predrag’s thread; I asked him about it because I know he likes diagrammatic methods.)

The diagrammatic methods for vector calculus and the diagrammatic methods for group representation theory are two aspects of the same game. Penrose invented these methods for tensor calculus, which combines vector calculus and group rep theory. So Predrag should like both.

Ok, thanks. I had not appreciated that the vector calculus diagrammatic methods were essentially the same thing as the methods for group theory.

Yeah, the cool thing is that all the usual operations in 3d vector calculus are covariant under 3d rotations, so they're all about "things you can do with representations of SO(3)". The all-important Levi-Civita symbol epsilon_{ijk} is the star of the show here.