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Robert Griffiths replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 9 years, 2 months ago
Dear Roderich,
In response to your #1899. Thanks for your clarification, but I am still unsure where you stand. Let us start with ‘English’ properties, by which I think you mean macroscopic properties. Will you allow me to assign things like “pointer is directed at the symbol L on the box” to a Hilbert subspace (of necessarily enormous…[Read more]
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Robert Griffiths replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 9 years, 3 months ago
Dear Roderich,
Again, relative to your #1857. Many people have the mistaken notion that spin half can contain large amounts of information because they visualize the quantum state as a classical arrow with a precise direction, or a classical spinning top with a precise axis of rotation. While such pictures are useful, they can mislead. In…[Read more]
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Robert Griffiths replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 9 years, 3 months ago
Dear Roderich,
Thank you for #1857. Let me take up the second topic first: properties of macroscopic systems. Since you believe that quantum theory applies at the macroscopic level, you need some way to represent properties on a Hilbert space, assuming you are not using hidden variables. I use projectors, because these are the ways properties…[Read more]
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Robert Griffiths replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 9 years, 3 months ago
Dear Roderich,
I find your reply to my comment interesting, but I wonder if you could elaborate on the following. My use of a subspace for a quantum property goes back to von Neumann, and I employ it at the microscopic level or spin half and at the macroscopic level, because I believe that quantum mechanics applies at all length scales, “from…[Read more]
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Robert Griffiths replied to the topic What did Bell really prove? in the forum John Bell Workshop 2014 9 years, 3 months ago
Dear Jean,
Your paper is very well written, and a pleasure to read. I thank you.
However, I think your arguments are more than a decade out of date. I analyzed the nonlocality issue of EPRB correlations in Chs. 23 and 24 of my book CONSISTENT QUANTUM THEORY (http://quantum.phys.cmu.edu/CQT), where I considered EPRB correlations, and…[Read more]
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Robert Griffiths started the topic What Does Bell's Theorem Really Tell Us? in the forum John Bell Workshop 2014 9 years, 3 months ago
The claim is often made that the violation of a Bell inequality by standard quantum mechanics (SQM), in agreement with experiments, means that there is an intrinsic nonlocality in the quantum world. I argue against this by examining some derivations of the Clauser-Horne-Shimony-Holt (CHSH) inequality using various assumptions. These indicate…[Read more]
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Robert Griffiths replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 9 years, 3 months ago
8 January 2015
Dear Roderich,
I am pleased to see that someone besides me thinks that Kolmogorov probabilities are not to be abandoned when discussing quantum mysteries. I have made careful use of them in demonstrating that quantum mechanics is local in a fairly precise sense of that term in an article you do not seem to be aware of, or at…[Read more]
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Robert Griffiths replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 9 years, 3 months ago
8 January 2015
Dear Richard, regarding your 1737,
I see no reason why in a relativistic world probabilities need teo be relativized to a particular spacetime point. That may be convenient for some purposes, but why is it needed in general? In a relativistic world, just as in a nonrelativistic world, you need to make clear what you are talking…[Read more]
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Robert Griffiths replied to the topic Local Causality, Probability and Explanation (Online 12/30 @ 2 p.m. UTC – 7 ) in the forum John Bell Workshop 2014 9 years, 3 months ago
8 Jan. 2015
Thank you, Prof. Ghirardi. That is precisely my point. I don’t see where
quantum mechnaics plays any essential role in Healey’s discussion. Have I missed something? Bob Griffiths -
Robert Griffiths replied to the topic A reasonable thing that just might work in the forum John Bell Workshop 2014 9 years, 3 months ago
6 January 2015
Dear Daniel,
I only recently got around to looking at your post. Here are some comments, numbered to help me keep them straight.
1. ‘Retrocausality’ means the future influencing the past, which sounds like science fiction. I think you should stick to ‘microscopic time-reversal symmetry’ as otherwise others will be as confused…[Read more]
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Robert Griffiths replied to the topic Local Causality, Probability and Explanation (Online 12/30 @ 2 p.m. UTC – 7 ) in the forum John Bell Workshop 2014 9 years, 3 months ago
Dear Richard,
Busy over year end, so only got to your post recently. Two comments
First, I couldn’t see why agents were really needed for the discussion unless one insists, like some do, that probabilities must be interpreted that way. Everything you said, it seemed to me, could very well be expressed in terms of conditional probabilities based…[Read more]
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Robert Griffiths joined the group John Bell Workshop 2014 9 years, 3 months ago
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Robert Griffiths joined the group John Bell Workshop 2014 9 years, 4 months ago
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Robert Griffiths replied to the topic Panel Discussion: How to make sense of the wave function? [Friday, EDT (UTC-4): 3pm-5pm] in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Correct ‘no’ to ‘know’ in the last line of #1144. RBG
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Robert Griffiths replied to the topic Panel Discussion: How to make sense of the wave function? [Friday, EDT (UTC-4): 3pm-5pm] in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Dear Lee,
My answer to the Dowker and Kent criticism is that the fact that there are alternative frameworks in no way invalidates the quasiclassical framework of Gell-Mann and Hartle. This has not convinced either of them. A not-too-lengthy discussion of things from my present perspective is in “The New Quantum Logic,” Found. Phys. 44 (June,…[Read more]
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Robert Griffiths replied to the topic Panel Discussion: How to make sense of the wave function? [Friday, EDT (UTC-4): 3pm-5pm] in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Dear Shan,
Before the final bell rings let me express what I am sure is the universal belief of the participants: We all appreciate the hard work you have done
in organizing things for this workshop. Thanks a great deal! -
Robert Griffiths replied to the topic Panel Discussion: How to make sense of the wave function? [Friday, EDT (UTC-4): 3pm-5pm] in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Dear Richard, re #1139
I advocate as the principled way the Single Framework Rule; at least that seems to allow in enough things for the physicist to do physics, and not so many that one ends up with insoluble paradoxes. The result, by the way, is
a satisfactory ability to do retrodiction, but without retrocausality, though some criticis of the…[Read more] -
Robert Griffiths replied to the topic Panel Discussion: How to make sense of the wave function? [Friday, EDT (UTC-4): 3pm-5pm] in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Dear Richard, re your #1134
I would agree that statements about what the measurement actually measured, when they are microscopic properties, need to be treated with caution and put in the proper framework or consistent family, and I think the experimentalists are correct (without being able to supply a full explanation of why they are correct)…[Read more]
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Robert Griffiths replied to the topic Panel Discussion: How to make sense of the wave function? [Friday, EDT (UTC-4): 3pm-5pm] in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Dear Richard,
I think your #1129 truncates the measurement problem. Not only do we want
the pointer to stop shaking, we want to learn something about the PREVIOUS state of the particle from the pointer’s later position. That’s how experimental physics is carried out, and most obviously so when the apparatus eats up the particle so it is not…[Read more] -
Robert Griffiths replied to the topic Panel Discussion: How to make sense of the wave function? [Friday, EDT (UTC-4): 3pm-5pm] in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Dear Richard,
Relative to your #1122. I think for most of us ‘the wave function’ is something we can imagine arising from some sort of preparation: Alice has a device that produces a spin-half particle with S_x = 1/2, and we assign a wavefunction to the particle, and maybe also to the apparatus that produces it and to the measurement apparatus,…[Read more]
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