They don't even have to be Feynman diagrams - theoretical (rather than mathematical) physicists are usually pretty lazy. We make up notation for us rather than

They don't even have to be Feynman diagrams - theoretical (rather than mathematical) physicists are usually pretty lazy. We make up notation for us rather than the reader. Mathematicians, I find, are a lot worse but still bearable. Engineers though, oh boy, seem to actively enjoy using notation to obscure the material in the books I have read.