# Reference recommendation for the study of simple Lie algebras

I'm a physics student trying to learn something about the classification of compact simple Lie algebras. I asked one of my TA's for a book recommendation and got Fulton's "Representation Theory". After giving it a shot and reading chapters 7 and 8 (with which's topics I'm already familiar with) I can't really say that I'm understanding a lot. It's hard to say why, but I guess I'm not a huge fan of the way how the author explains (words) things, and I'm missing the mathematical structure (Lemma, Prop., Thm, Proof, etc.).

Googling the topic gives a lot of results, but many of these are semester projects or thesis from other people and not really textbooks. I don't mind reading those, but I'm not really sure if these are the most pedagogical approach to learn something about the topic. Some of the above mentioned semester projects/thesis:

The last one actually looked quite promising, but I haven't really had time to check it in a bit more detail. My question therefore boils down to: What textbooks/references can you recommend for the topic "Classification of compact simple Lie algebras"?

PS:

• I've already had a proper two semester course on representation theory, starting with groups and their properties in a abstract form, then to represenations in general, then to Lie algebra representations, etc. So I have some basic understanding about these things. I saw that in the context of representation theory some concepts of differential geometry are mentioned (manifolds, differentials, etc.), you can also assume that a basic knowledge is present in this area as well.
• I've seen this question, which kind of relates to mine, but it seems to focus on much narrower questions than mine, so I don't really think it qualifies as duplicate.
• That is a difficult question. Usually people interested in Lie algebras are either physicists who want something in the style of the Georgi classic (Lie Algebras in Particle Physics) or pure mathematicians who want the Lie Group material covered in depth. I agree with you that the Fulton book is an odd choice for Lie Algebras (even though I like it for other reasons). Commented Jan 30, 2020 at 14:43
• On top of Dietrich Burde's excellent pointers here, compare the answers to math.stackexchange.com/q/3121110/96384. Commented Jan 30, 2020 at 17:35