# Lie algebra (quick question)

1. Dec 29, 2011

### romsofia

Sorry for such a simple question, usually I'd go to my physics teacher for help on this question, but it's break and I really don't know the answer.

I'm currently studying from an online book (http://www.math.harvard.edu/~shlomo/docs/lie_algebras.pdf) and on the bottom of page 8 he states "Let ad A denote the operation of bracketing on the left by A, so adA(B) := [A, B]"

Is this implying [A,B] is the lie bracket (pretty sure this is the case, but better to ask then mislead myself!), and what does the ad mean (nothing comes to mind)?

Thanks for the help!

2. Dec 29, 2011

### Square

3. Dec 29, 2011

### romsofia

That would make sense for it be adjoint endomorphism after a quick skim of the wikipedia page (however, I have never heard of the term)! Thanks for you time.