What is the name of the formula on the picture Electron (painting from the Hungarian painter Oliver Sin)?

Question

jamesj · Answer

?

anonymous · Answer

On the left hand side is energy minus rest energy, written according to special relativity.  On the right side, I'm not sure, it looks a little like an operator for the potential energy, particularly given the e there.

My first guess is that it might be some fragment of equation from the first attempts to write a relativistic theory of the electron, before the Dirac equation.  That's because of the line drawn through the formula, as if it was found to be wrong and discarded.