The Standard Model

This is the fascinating story of the development of Standard Model of particle physics between Dirac's prediction of the positron in 1928 and the introduction of the six-quark model in 1973. The Standard Model of particle physics is the theory describing three of the four known fundamental forces in the universe (electromagnetic, weak and strong interactions - excluding gravity), and classifying all known elementary particles. Although the Standard Model has demonstrated some success in providing experimental predictions, it falls short of being a complete theory of fundamental interactions. Part I describes the development of the Standard Model from the Bohr model of the atom in 1913, based on what were believed to be 3 stable particles, electrons in orbit around a nucleus comprised of protons and neutrons, to its emergence in 1973 as the six-quark model, comprising 52 elementary particles and anti-particles, of which only the electron is believed to be stable. Part III, which was previously Part II, introduced an alternative to the Standard Model, Supersymmetry; and Part IV, which was previously Part II, introduced, String Theory.
The Second Edition includes a new PART II on Unified Gravity, describing two recent papers by Partanen, M. & Tulkki, J. The innovation of most interest is their introduction in the March, 2024 paper of an eight-component spinorial wave equation of the electromagnetic field and the application of this to produce an eight-component spinorial (non-relativistic) formulation of Maxwell's equations in which the four equations are represented by a single eight-component spinorial equation. The second paper attempted to use this to derive a gauge theory of gravity called unified gravity using compact, finite-dimensional symmetries, in which the metric tensor entered through geometric conditions. The Second Edition also includes a description of the Lagrangian on pages 20-1.