- #1

asimov42

- 377

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- TL;DR Summary
- Seems to be opposite QFT - unclear about Feynman diagrams...

I've been struggling with a somewhat-recent paper by Charles Francis, "A construction of full QED using finite dimensional Hilbert space," available here: https://arxiv.org/pdf/gr-qc/0605127.pdf

But also published in https://www.researchgate.net/journal/1729-5254_Electronic_Journal_of_Theoretical_Physics 10(28):27–80 · May 2006.

Francis introduces a lattice-based technique of sorts, based on

Note that: "The fundamental physical concepts are particles, and Feynman diagrams have a natural interpretation in terms of interactions between particles in the absence of spacetime background. The predictions of perturbative QED are unaltered."

I'm bothered by Section 7.4 of the paper (Finite quantum electrodynamics - Interpretation of Feynman diagrams), where the author states that: "In standard treatments of QED, Feynman diagrams are regarded merely as aids to calculation, not descriptions of underlying structure. By contrast, in this treatment the perturbation expansion is interpreted directly as a quantum-logical statement, meaning that any number of interactions might be found taking place at any time and any position if we were to do a measurement ... in a particle interpretation, Feynman diagrams also give a pictorial representation of the fundamental structure of matter."

The above to me seems like a major step back from QFT, and also like ontological status is given to individual Feynman diagrams (a no-no, I thought). I'm not sure at all what this says about virtual particles, etc. If anyone is will to have a look and chime in (@A. Neumaier perhaps in particular!) I'd be grateful.

But also published in https://www.researchgate.net/journal/1729-5254_Electronic_Journal_of_Theoretical_Physics 10(28):27–80 · May 2006.

Francis introduces a lattice-based technique of sorts, based on

*measurement limitations.*Space is also not fundamental -> "In the present treatment quantum properties are understood to arise precisely because space does not appear as a fundamental physical concept. Measurement results are seen as relationships between the matter (or radiation) under study and reference matter 3 used to defined the measurement"Note that: "The fundamental physical concepts are particles, and Feynman diagrams have a natural interpretation in terms of interactions between particles in the absence of spacetime background. The predictions of perturbative QED are unaltered."

I'm bothered by Section 7.4 of the paper (Finite quantum electrodynamics - Interpretation of Feynman diagrams), where the author states that: "In standard treatments of QED, Feynman diagrams are regarded merely as aids to calculation, not descriptions of underlying structure. By contrast, in this treatment the perturbation expansion is interpreted directly as a quantum-logical statement, meaning that any number of interactions might be found taking place at any time and any position if we were to do a measurement ... in a particle interpretation, Feynman diagrams also give a pictorial representation of the fundamental structure of matter."

The above to me seems like a major step back from QFT, and also like ontological status is given to individual Feynman diagrams (a no-no, I thought). I'm not sure at all what this says about virtual particles, etc. If anyone is will to have a look and chime in (@A. Neumaier perhaps in particular!) I'd be grateful.