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A. Neumaier
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The wording is mine, but the meaning is the same. An open system is dissipative, and dissipation is just the form an incomplete collapse takes. The equations for open systems and the equations for objective collapse http://en.wikipedia.org/wiki/Ghirardi-Rimini-Weber_theory are essentially of the same form. The main difference is that objective collapse theories believe that collapse happens at the most fundamental level, while the general theory of open systems takes its equations to be just as empirically validated rather than as fundamental, and often derives it under some plausibility assumptions (that are difficult to justify rigorously) from an underlying Schroedinger equation.akhmeteli said:Thank you very much for the references. I'm still not sure though. Those references do not seem to have wordings similar to what you offer: "There is universal agreement that collapse is _observable_ in open systems" .
This just means that the collapse is only approximate, but to a very good approximation. The collapse in the Copenhagen interpretation also happens gradually, in the course of completing a measurement; it is instantaneous only in the unphysical idealization that a measurement takes no time.akhmeteli said:Furthermore, everybody emphasizes that the transition from one state to another is fast, but continuous
What happens during the measurement duration is not specified by the Copenhagen interpretation, and therefore can well be continuous.
Just like all claims made in physics - I never heard even a single claim that models used in physics are accurate to infinite number of digits!akhmeteli said:(so theoretically there is always a superposition); therefore, the only thing one can say is that under some conditions collapse can be a good approximation.
The equations used for the quantitatively correct modeling of open system are without exception non-unitary. Unitary evolution is at best claimed for the much bigger, practically unobservable system composed of the actually observed system and its environment.akhmeteli said:No authors of your references seem to claim any experimental deviations from unitary evolution.
Well, if you take both unitary evolution and the projection postulate as absolute truth, exact to infinitely many decimal places, you get a contradiction. But it is ridiculous to regard it as that. There have been many measurements of spectroscopic energy levels, but none of them produced an exact infinite decimal expansion of a discrete eigenvalue of the Hamiltonian (normalized to ground state zero) as would be required by the Born rule as typically stated in textbooks. This shows that these postulates must be regarded as approximations.akhmeteli said:On the other hand, unitary evolution directly contradicts strict collapse, as defined in the projection postulate.
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