Modern Physics: One-Pager#
This is a sketch of the mathematics behind the Physics Roadmap. Sorry for my poor handwriting, a clean version is on my to-do list. The figure shows four quadrants: Newtonian mechanics (N, top left); special relativity (SR, bottom left), quantum mechanics (QM, top right), and quantum field theory (QFT, bottom right). The overarching principle is that of least action, famously presented in Chapter 19 of [Feynman et al., 1963], and we encounter several varieties of the equations of motion (Newton, Hamilton, Schrödinger, Einstein, Klein–Gordon, and Dirac).