Lectures on quantum field theory

" Dirac's life-long (1948-1984) and relentless pursuit for a quantum electrodynamics with a logical footing"

In the 1950’s in his search for a better QED, Paul Dirac developed the Hamiltonian theory of constraints (Cand J Math 1950 vol 2, 129; 1951 vol 3, 1) based on lectures that he delivered at the 1949 International Mathematical Congress in Canada. Although Dirac, like Einstein, would never jump on the band wagon, it is not simply true that he was not aware of particles called mesons ( see Farmelo G 2009 "The Strangest Man", London Faber & Faber). Dirac (1951 “The Hamiltonian Form of Field Dynamics” Cand Jour Math, vol 3 ,1) had also solved the problem of putting the Tomonaga-Schwinger equation into the Schrödinger representation ( See Phillips R J N 1987 “Tributes to Dirac” p31 London:Adam Hilger) and given explicit expressions for the scalar meson field (spin zero pion or pseudoscalar meson ), the vector meson field (spin one rho meson), and the electromagnetic field (spin one massless boson,photon) . Dirac had met Feynman in 1961 and the two physicists talked about the non-existence of an equation “similar to the relativistic equation of the electron” describing a meson which apparently Feynman was supposed to be working on! Feynman started the conversation with the question “It must be good to have invented that equation ”. J C Polkinghorne admitted how wrong he was about Dirac and contemporary particle physics in an article in Kursunoglu & Wigner (Ed) 1990 "Reminiscences about a great physicist" p228 Cambridge:CUP..quote... “All very clever”, we thought to ourselves, " but Dirac would probably not know a pion if he saw one”. The last laugh is where it ought to be, with the great and insightful not tossed about by every wind of physical fashion but profound in his understanding of the quantum field theory that he had invented. I realize now ,with hindsight, that I heard Dirac talk about monopoles and the quantum mechanics of constrained and