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Unformatted text preview: Answers to Physics 176 One-Minute Questionnaires Lecture date: February 17, 2011 What is the flavor of Feynmans particle theory? As in, how did he go about showing it? After talking with some colleagues and finding some information on the Internet, I found that what I knew about Feynmans ideas was not quite correct. First, it was evidently not Feynman but his PhD advisor, Professor John Wheeler, who suggested to Feynman that one reason why all particles could be exactly identical is that they are all the same particle, but traveling back and forth in time. Second, the formalism of quantum electrodynamics (the quantum theory of photons and electrons) formally allows particles to go back in time in just the same way that Newtons equations of motion allow particles to go backwards in time, simply by reversing the sign of the time variable t everywhere in the dynamical equations. But in QED, an electron going back in time appears as a positron (posi- tive antimatter particle) and vice versa (positrons going back in time behave like electrons). So one reason why the theory cant be correct is that it pre- dicts that there should be equal numbers of positrons and electrons, while only electrons are observed except in rare collisions with enough energy to produce positrons. Could you briefly explain why identical particles have to be exactly identical? I dont know of an elementary argument that would be insightful for you. Quantum field theory, which is the foundation of quantum electrodynamics (the theory of electrons and photons), quantum chromodynamics (the theory of the strong interaction, in which quarks interact to form protons, neutrons, mesons, and other baryonic matter), and the Standard Model (unified the- ory of electromagnetic, weak, and strong interactions) shows that massive particles like an electron or proton arise from the empty vacuum by a par- ticular mathematical mechanism that requires that all particles of a certain...
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