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Register a new userA quantum mechanism underlying the gauge symmetry in quantum electrodynamics
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Authors
Wen-ge Wang
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In this paper, a formulation, which is completely established on a quantum ground, is presented for basic contents of quantum electrodynamics (QED). This is done by moving away, from the fundamental level, the assumption that the spin space of bare photons should (effectively) possess the same properties as those of free photons observed experimentally. Within this formulation, bare photons with zero momentum can not be neglected when constructing the photon field; and an explicit expression for the related part of the photon field is derived. When a local gauge transformation is performed on the electron field, this expression predicts a change that turns out to be equal to what the gauge symmetry requires for the gauge field. This gives an explicit mechanism, by which the photon field may change under gauge transformations in QED.
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The ether concept -- abandoned for a long time but reinstated by Dirac in 1951-1953 -- has in recent years emerged into a fashionable subject in theoretical physics, now usually with the name of the Einstein-Dirac ether. It means that one special inertial frame is singled out, as the rest frame. What is emphasized in the present note, is that the idea is a natural example of the covariant theory of quantum electrodynamics in media if the refractive index is set equal to unity. A treatise on this case of quantum electrodynamics was given by the present author back in 1971, published then only within a preprint series. The present version is a brief summary of that formalism, with a link to the original paper. We think it is one of the first treatises on modern ether theory.
The duality symmetry between electricity and magnetism hidden in classical Maxwell equations suggests the existence of dual charges, which have usually been interpreted as magnetic charges and have not been observed in experiments. In quantum electrodynamics (QED), both the electric and magnetic fields have been unified into one gauge field $A_{mu}$, which makes this symmetry inconspicuous. Here, we recheck the duality symmetry of QED by introducing a dual gauge field. Within the framework of gauge-field theory, we show that the electric-magnetic duality symmetry cannot give any new conservation law. By checking charge-charge interaction and specifically the quantum Lorentz force equation, we find that the dual charges are electric charges, not magnetic charges. More importantly, we show that true magnetic charges are not compatible with the gauge-field theory of QED, because the interaction between a magnetic charge and an electric charge can not be mediated by gauge photons.
At the foundation of modern physics lie two symmetries: the Lorentz symmetry and the gauge symmetry, which play quite different roles in the establishment of the standard model. In this paper, it is shown that, different from what is usually expected, the two symmetries, although mathematically independent of each other, have important overlap in their physical effects. Specifically, we find that the interaction Lagrangian of QED can be derived, based on the Lorentz symmetry with some auxiliary assumption about vacuum fluctuations, without resorting to the gauge symmetry. In particular, the derivation is based on geometric relations among representation spaces of the SL(2,C) group. In this formulation of the interaction Lagrangian, the origin of the topological equivalence of the eight basic Feynman diagrams in QED can be seen quite clearly.
Gauge invariance, a core principle in electrodynamics, has two separate meanings, only one of which is robust. The reliable concept treats the photon as the gauge field for electrodynamics. It is based on symmetries of the Lagrangian, and requires no mention of electric or magnetic fields. The other depends directly on the electric and magnetic fields, and how they can be represented by potential functions that are not unique. The first gauge concept has been fruitful, whereas the second has the defect that there exist gauge transformations from physical to unphysical states. The fields are unchanged by the gauge transformation, so that potentials are the necessary guides to correctness.
Decompositional equivalence is the principle that there is no preferred decomposition of the universe into subsystems. It is shown here, by using simple thought experiments, that quantum theory follows from decompositional equivalence together with Landauers principle. This demonstration raises within physics a question previously left to psychology: how do human - or any - observers agree about what constitutes a system of interest?
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