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Nature Physics on quantum foundations
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[QUOTE="WernerQH, post: 6800698, member: 686891"] Thank you for the reference. I've seen Fröhlich's paper before, and I sympathize with his philosophy, but my notion of event is much more primitive: a point in space-time where a field excitation is created or destroyed. For me the creation of a photon is a real physical event, but it does not happen in an instant. It is a composite event. In a medium with a refractive close to 1, the emissivity (##{\rm W~m^{-2}~Hz^{-1}~sr^{-1}}##) can be written as $$ \epsilon = { \mu_0 \omega^2 \over 8 \pi^2 c} \sum_{\mu\nu} {\bf e}_\mu^* {\bf e}_\nu \int_{-\infty}^{\infty} dt \int d^3x\ e^{-i(kx - \omega t)} \langle j_\nu(0,0) j_\mu(x,t) \rangle $$ suggesting that an emission event actually comprises four primitive (strictly localized) events (## \Psi,\Psi^\dagger,\Psi,\Psi^\dagger ##). Between the times (events) ##j(0)## and ##j(t)## the "state" of the system, whether the photon has been created or not, is in limbo. Evolution is not strictly Markovian. It takes a short, but non-zero time until a fact ("photon has been emitted") is established. And experiments are always reported post factum. :-) Absolutely. Continuous and deterministic evolution according to Schrödinger's equation does not square with the graininess and randomness that we experience in the real world. I agree with Fröhlich that it is an intellectual scandal that it still seems necessary to graft extra "measurement" processes on the evolution of the real world. [/QUOTE]
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