Coxeter and Dynkin diagrams classify some of the most beautiful objects in mathematics. Here I use Dynkin diagrams to classify compact Lie groups—and especially compact semisimple Lie groups.
This is one of a series of lectures at the University of Edinburgh on topics drawn from my column This Week’s Finds:
http://math.ucr.edu/home/baez/twf/
Cover image by Tom Ruen, CC BY-SA 4.0