The Kepler Problem (Part 8)

Now comes the really new stuff. I want to explain how the hydrogen atom is in a certain sense equivalent to a massless spin-½ particle in the ‘Einstein universe’. This is the universe Einstein believed in before Hubble said the universe was expanding! It has a 3-sphere for space, and this sphere stays the same size as time passes.

Today I’ll just lay the groundwork. To study relativistic spin-½ quantum particles, we need to understand the Dirac operator. So, we need to bring out the ge...