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Cosmology, Quantum Mechanics & Consciousness Message Board › Back to some Real Quantum Mechanics - Quantum Interference - The Movie...

Back to some Real Quantum Mechanics - Quantum Interference - The Movie...

lan B.
user 10895495
London, GB
Post #: 215

Well it's a stupid rule and I didn't know it. Furthermore, during the past week or so I've posted one or two other links which have evidently been completely wasted. Anyway, in the meantime I've solved the problem, finally ..­



A former member
Post #: 139
Gosh, you are really in a nice mood Ian, suggesting now that I am too lazy to check out Omnes on the internet. Wrong yet again! You should stop second-guessing people, it’s not one of your strengths. For your information I did read up about him a few weeks ago and I did then encounter that book review that you mentioned. That small amount of background work was enough to tell me that Omnes has not been one of the big hitters in the QM game. And actually, the fact that you have given just one useful web reference which just happens to be the same as the only good one that I could find does rather support my view that this author is not in the big league.

I’m sure that decoherence theory gives a decent explanation of how bizarre quantum behaviour at the smallest scales carries over into the classical world that we observe. But it seems to me that it cannot be a complete and definitive re-interpretation of QM because (so far as I know) it cannot replicate the maths correctly and also because Stanford Enc explicitly and firmly says so.

That review of the Omnes book looks like a conscientious and insightful piece of writing. On the basis of this review I would expect the book itself to be a good work, exactly as you have said up to 40 times already. My quick impression is that Omnes has put together a cohesive account of QM in terms of ‘consistent histories’ and decoherence. But from what little I’ve read and understood about ‘consistent histories’ after a brief acquaintance, I am not so far impressed that this is really much progress over the Copenhagen interpretation. In particular I draw to your attention the fact that Omnes has not dispensed with the operator formalism and the associated Process 1. He has renamed them instead! He has replaced ‘wave collapse’ with a multiplicity of operators and Process 1 events, corresponding to the multiplicity of minor entanglement events that occur during quantum decoherence. All good stuff, but no radical change from Copenhagen.

Omnes renames Process 1, or the mini-versions of Process 1 during decoherence, as ‘actualisation’. The reviewer then says of Omnes’ rule 5: “This statement by itself does not give a clear picture of the mathematical formulation of actualization.” Quite so: Process 1 and the associated projection operators are all there in the book, apparently conjured out of thin air just like Dirac or von Neumann. There is no new explanation here of the basics of what is going on in QM. Is there?

In your posting #157 on this QM thread you said, Ian: “The whole point about decoherence is that there is no collapse of the wavefunction”. Well that is clearly your point about decoherence but it appears from the review of Omnes that what he calls ‘actualisation’ is the same concept as ‘wave collapse’, subject to the refinement that a lot of individual ‘actualisations’ compound over the decoherence process to produce the effect known as ‘wave collapse’. I have issued a repeated challlenge to show me how decoherence can emulate Process 1. Perhaps the answer from Omnes' book is that when you analyse the detail, you will find that the overall Process 1 is replicated by a lot of actualisations. Yes, I would accept such an explanation, but then I would say that decoherence in these terms is basically a worked-through elaboration of the Copenhagen model using a lot of little 'wave-collapses'. Which then add up to the big wave collapse. So decoherence doesn't explain it away, does it?

By the way I can copy and paste as well as you; here are the closing remarks of the book review:

“But the core resolution is merely a desperate bluff. ....................The bluff lies in such statements as: “the actuality of facts is something that need not be explained by a theory,” and “when one finds a gap between theory and reality only at their common extremities, this is not a failure but the mark of an unprecedented success for quantum mechanics, as compared with all the theories before it.” The fact that an obviously competent physicist is driven to such assertions is evidence that the quantum theory remains in conceptual murk. The challenge remains: interpret quantum mechanics on its own terms, without appeal to authority, in a way that makes sense to reasonable people. This challenge has not yet met an adequate response.”

Quite so Mr Reviewer, I heartily endorse your general sentiments. And please tell me, Ian, which of the recognised quantum interpretations do you actually favour, wave-collapse or no-collapse or lots of little collapses? I look forward to the clarification.

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