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pragmatist comments on What independence between ZFC and P vs NP would imply - Less Wrong Discussion

1 Post author: alexflint 08 December 2011 02:30PM

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Comment author: shminux 09 December 2011 07:32:05AM *  0 points [-]

I suspect that he misinterprets, as it were, what an interpretation is, namely, a way of thinking that elucidates the underlying mathematical framework. He seems to think that different interpretations can make different predictions based on the same math:

We are led by the Copenhagen Interpretation to expect that the positions of the interference minima should have no particular significance, and that the wires should intercept 6% of the light they do for uniform illumination.

...

Thus, it appears that both the Copenhagen Interpretation and the Many-Worlds Interpretation have been falsified by experiment.

Does this mean that the theory of quantum mechanics has also been falsified? No indeed! The quantum formalism has no problem in predicting the Afshar result. A simple quantum mechanical calculation using the standard formalism shows that the wires should intercept only a very small fraction of the light. The problem encountered by the Copenhagen and Many-Worlds Interpretations is that the Afshar Experiment has identified a situation in which these popular interpretations of quantum mechanics are inconsistent with the quantum formalism itself.

I would say that, more likely than not, his mental model of what an interpretation is is different from what physicists tend to mean. It does not help that he has an ax to grind, as the author of his pet "transactional" interpretation.

Comment author: pragmatist 10 December 2011 03:59:51AM *  1 point [-]

Copenhagen and Many Worlds do not employ the same math. Many Worlds posits a single dynamical evolution law, given by Schrodinger's equation. Copenhagen supplements this with an intermittent stochastic collapse process (Von Neumann's Process 2). So Copenhagen vs. MWI is a question open to empirical test.

There are certain interpretations that are empirically indistinguishable from MWI. Bohmian mechanics is an example, although even here the math is different but this difference is postulated to be epistemically inaccessible.

EDIT: I think calling Copenhagen, MWI, Bohm, GRW, etc. different interpretations of a single theory is pretty misleading, suggesting that they are different models of the same axiomatic system. They should really be regarded as different theories, with a large amount of overlap in their mathematical structure.

Comment author: shminux 11 December 2011 12:58:24AM 1 point [-]

There is no "intermittent stochastic collapse process" anywhere in the math of QM. The measurement is a black box with the Born rule to decide the outcome. Bohm is a different story, and not a happy one.

Comment author: pragmatist 12 December 2011 05:53:10AM 0 points [-]

The measurement process in the orthodox interpretation isn't just a means for determining outcomes. It also has an effect on the subsequent evolution of the wave function. There is a discontinuity in the dynamics before and after a measurement. I don't see how that wouldn't count as part of the math of the theory.

Comment author: shminux 12 December 2011 08:02:52AM *  0 points [-]

True, but there is nothing stochastic about this. Measurement is an external event controlled by an observer. The Born rule and the jump into an eigenstate is the math of it, nothing more, nothing less. The "Von Neumann's Process 2" is an unnecessary interpretational mumbo-jumbo.

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