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What is the default position in the mind-body problem?

siti

Well-Known Member
What is measured in the tests of the Bell and Leggett-Garg inequalities is whether the results are consistent with or violate the inequalities.

Do you understand that the correlations between Alice's findings and Bob's findings are not the effect of matter or energy?
You can't measure "inequalities" and "violations" - you have to measure physical things - matter/energy things like "photons" for example.

Yes I do understand that they are not the effect of classical physical processes...but there is no measurement that is not performed physically and no experiment that is not initiated physically - so how do we know that any of the quantum mechanical effects that are observed could happen in the absence of physical reality? "Particles" and their "properties" may be non-realistic and non-local, but in the end I reckon that just means we don't understand reality well enough to describe it properly.
 

Polymath257

Think & Care
Staff member
Premium Member
And you claim that "matter and energy don't have the properties of the classical viewpoint". Prove your claim that matter and energy do not propogate at finite speeds.

I never claimed that. In fact, I claimed exactly the opposite. Since QM is a local thoeyr, all information propagates at speeds less than that of light.

Then how do you account for the correlations that violate the postulates of locality and realism as defined by Bell and Leggett-Garg inequalities?
Those correlations violate the combination of locality and realism. Quantum mechanics is a local, non-realist description.

Above I noted what Bell said about the theorem that he proved: "If [a hidden variable theory] is local it will not agree with quantum mechanics, and if it agrees with quantum mechanics it will not be local. This is what the theorem says." So you're saying that Bell was just wrong about QM being a nonlocal theory?

What Bell said is correct. But your interpretation is wrong. There is no local hidden-variable (i.e, realistic) theory that agrees with the predictions of quantum mechanics. But QM is NOT a hidden variable theory. It *is* local, but it is not realistic.

And I linked to a paper on an experiment that found that the collapse of the wavefunction of a single photon is nonlocal. And you are saying that that is wrong?

Yes. It is a misinterpretation. The wave function describes the probabilities and correlations. Those probabilities and correlations propagate at less than the speed of light.

In these experiments, a correlation is set up in an entangled pair. Later, an observation is made of one of the pair and either later or in a different location, an observation is made of the other partner. A correlation is found in some properties of the two particles, usually the spin.

What locality means in this context is that the results of the first observation will not change the local results of the other observation. It is only when the two sets of results are brought together that the correlation is revealed. if you are *only* looking at the second set of observations, there is no way to tell that the first set of observations was done nor what the outcomes were for it.
 

Polymath257

Think & Care
Staff member
Premium Member
What is measured in the tests of the Bell and Leggett-Garg inequalities is whether the results are consistent with or violate the inequalities.

Right. And the observed results show that no local realistic description (i.e, a hidden variable theory) can explain these results.

Do you understand that the correlations between Alice's findings and Bob's findings are not the effect of matter or energy?

Wrong. The correlations were established when the entangled pair is formed. That *is* a property of the matter and energy of that system: that the resulting pair of particles will be entangled.
 

Nous

Well-Known Member
Premium Member
You can't measure "inequalities" and "violations"
Tell it to the physicists:

Bell’s theorem states that quantum mechanics is incompatible with local realism. He showed that if we assume, in line with Einstein’s theory of relativity, that there are no physical influences traveling faster than the speed of light (the assumption of locality) and that objects have physical properties independent of measurement (the assumption of realism), then correlations in measurement outcomes from two distant observers must necessarily obey an inequality[4]. Quantum mechanics, however, predicts a violation of the inequality for the results of certain measurements on entangled particles. Thus, Bell’s inequality is a tool to rule out philosophical standpoints based on experimental results. Indeed, violations have been measured.​

https://arxiv.org/pdf/1511.03190

- you have to measure physical things - matter/energy things like "photons" for example.
Energy and momentum are just abstract quantities.
 

Nous

Well-Known Member
Premium Member
And you claim that "matter and energy don't have the properties of the classical viewpoint". Prove your claim that matter and energy do not propogate at finite speeds.
I never claimed that. In fact, I claimed exactly the opposite.
In #269, you stated: “But matter and energy don't have the properties of the classical viewpoint.”

And in #274, you stated: “The classical viewpoint has matter made of particles with unique properties where the forces are propagated at finite speeds”

What Bell said is correct. But your interpretation is wrong. There is no local hidden-variable (i.e, realistic) theory that agrees with the predictions of quantum mechanics. But QM is NOT a hidden variable theory.
Bell clearly states that "If [a hidden variable theory] is local it will not agree with quantum mechanics . . ."

You should work on getting more comfortable with the facts.

Yes. It is a misinterpretation. The wave function describes the probabilities and correlations. Those probabilities and correlations propagate at less than the speed of light.
Apparently you are trying to knock down a straw man. Note the description of Einstein's objection to QM with which this paper begins:

Einstein never accepted orthodox quantum mechanics because he did not believe that its nonlocal collapse of the wavefunction could be real. When he first made this argument in 1927 (ref. 1), he considered just a single particle. The particle’s wavefunction was diffracted through a tiny hole so that it ‘dispersed’ over a large hemispherical area before encountering a screen of that shape covered in photographic film. Since the film only ever registers the particle at one point on the screen, orthodox quantum mechanics must postulate a ‘peculiar mechanism of action at a distance, which prevents the wave... from producing an action in two places on the screen’1. That is, according to the theory, the detection at one point must instantaneously collapse the wavefunction to nothing at all other points.​

Experimental proof of nonlocal wavefunction collapse for a single particle using homodyne measurements : Nature Communications

It's the collapse of the wavefunction that is nonlocal--even the wavefunction of a single particle, as this study demonstrates.

In these experiments, a correlation is set up in an entangled pair.
Not in the experiment just noted.
 

Nous

Well-Known Member
Premium Member
Do you understand that the correlations between Alice's findings and Bob's findings are not the effect of matter or energy?
Wrong. The correlations were established when the entangled pair is formed. That *is* a property of the matter and energy of that system: that the resulting pair of particles will be entangled.
Hello? You have just denied that the realism postulate is violated!

The wavefunction does not determine that Alice will get spin up for any particular measurement. It only determines that when she does get spin up, Bob will get spin down, even when he is space-like separated from her.

Let us review how these experiments are performed (my underlining):

At equal distances from the source we shall suppose that there are two detectors, [A] and [B ], at rest with respect to the source. [. . .] Agents Mulder and Scully respectively, patiently writing down the results of each run of the apparatus. Mulder is holding his detector at a constant angle, while Scully varies her detector angle from time to time, hoping to send a message to her partner.

We know that the results recorded by Mulder and Scully will be correlated. To be a bit more specific, if the particles are fermions of spin 1/2, and if we are recording spin up or down in a particular direction, then the correlation will be given by −cosθAB, where θAB is the relative angle between the two detectors. We know that this correlation violates a Bell Inequality [1, p. 140–147], and we know that this means that the particular results our two agents get could not have been encoded in the particles when they left the source.


https://arxiv.org/pdf/quant-ph/9906036

(The thesis of that paper--"that most or all no-signalling proofs to date are question-begging, in that they depend upon assumptions about the locality of the measurement process that needed to be established in the first place"--is quite interesting.)
 

Polymath257

Think & Care
Staff member
Premium Member
Tell it to the physicists:

Bell’s theorem states that quantum mechanics is incompatible with local realism. He showed that if we assume, in line with Einstein’s theory of relativity, that there are no physical influences traveling faster than the speed of light (the assumption of locality) and that objects have physical properties independent of measurement (the assumption of realism), then correlations in measurement outcomes from two distant observers must necessarily obey an inequality[4]. Quantum mechanics, however, predicts a violation of the inequality for the results of certain measurements on entangled particles. Thus, Bell’s inequality is a tool to rule out philosophical standpoints based on experimental results. Indeed, violations have been measured.​

https://arxiv.org/pdf/1511.03190

Energy and momentum are just abstract quantities.

Yes, again, local realism is false. There are many experiments that show that you cannot have a theory that is *both* local and realist. That means that any correct description is either not local *or* not realist. Quantum mechanics is not realist. But it *is* local. So it is not local realist.
 

Polymath257

Think & Care
Staff member
Premium Member
In #269, you stated: “But matter and energy don't have the properties of the classical viewpoint.”

And in #274, you stated: “The classical viewpoint has matter made of particles with unique properties where the forces are propagated at finite speeds”

OK, you have a consistent issue that I have noticed. Suppose I say that 'A and B' is a false statement. That does NOT require A and B are both false. It means that A is false or B is false or both.

So, when I say that the classical description 'particles have unique properties and forces are propagated at finite speeds', to deny that means that either 'particles do not have definite properties' or that 'some forces do not propagate at finite speeds' or both.

In this case, the negation is correct because particles do not have definite properties.

Bell clearly states that "If [a hidden variable theory] is local it will not agree with quantum mechanics . . ."

You should work on getting more comfortable with the facts.
And quantum mechanics is not a hidden variable theory. It *is* local, bit it is not realist.

Apparently you are trying to knock down a straw man. Note the description of Einstein's objection to QM with which this paper begins:

Einstein never accepted orthodox quantum mechanics because he did not believe that its nonlocal collapse of the wavefunction could be real. When he first made this argument in 1927 (ref. 1), he considered just a single particle. The particle’s wavefunction was diffracted through a tiny hole so that it ‘dispersed’ over a large hemispherical area before encountering a screen of that shape covered in photographic film. Since the film only ever registers the particle at one point on the screen, orthodox quantum mechanics must postulate a ‘peculiar mechanism of action at a distance, which prevents the wave... from producing an action in two places on the screen’1. That is, according to the theory, the detection at one point must instantaneously collapse the wavefunction to nothing at all other points.​

Experimental proof of nonlocal wavefunction collapse for a single particle using homodyne measurements : Nature Communications

It's the collapse of the wavefunction that is nonlocal--even the wavefunction of a single particle, as this study demonstrates.

Not in the experiment just noted.

There is nothing non-local going on here. Read the links I gave before. Only one particle goes through, so only one particle is detected. It is detected on one side or the other.

Also, notice that Bob cannot determine what Alice does based *only* on his own measurements. No matter what Alice does, Bob's results look the same. it is only when Bob and Alice's results are compared that the correlation between the two sides is revealed.

Now, this experiment *does* show (again) that classical views of how particles work fail. There is a *single* wave function that encompasses both Bob and Alice. That single wave function describes *both* sides of the experiment.
 

Polymath257

Think & Care
Staff member
Premium Member
Hello? You have just denied that the realism postulate is violated!

No, I did not. The entanglement does NOT determine the results of the later observations. It only determines the probabilities and correlations.

The wavefunction does not determine that Alice will get spin up for any particular measurement. It only determines that when she does get spin up, Bob will get spin down, even when he is space-like separated from her.

Yes. Exactly. And that correlation (anti-correlation) is determined when the entangled particles are formed.

Let us review how these experiments are performed (my underlining):

At equal distances from the source we shall suppose that there are two detectors, [A] and [B ], at rest with respect to the source. [. . .] Agents Mulder and Scully respectively, patiently writing down the results of each run of the apparatus. Mulder is holding his detector at a constant angle, while Scully varies her detector angle from time to time, hoping to send a message to her partner.

We know that the results recorded by Mulder and Scully will be correlated. To be a bit more specific, if the particles are fermions of spin 1/2, and if we are recording spin up or down in a particular direction, then the correlation will be given by −cosθAB, where θAB is the relative angle between the two detectors. We know that this correlation violates a Bell Inequality [1, p. 140–147], and we know that this means that the particular results our two agents get could not have been encoded in the particles when they left the source.


https://arxiv.org/pdf/quant-ph/9906036

(The thesis of that paper--"that most or all no-signalling proofs to date are question-begging, in that they depend upon assumptions about the locality of the measurement process that needed to be established in the first place"--is quite interesting.)

Yes. The two sides are *correlated*.

But, suppose we only look at one side. Can Mulder, by only looking at his results, tell what Scully is doing? The answer is no. Can Scully, looking only at her results, tell what Mulder is doing? No.
No measurement that Scully does can be detected by Mulder, even at the level of changing his probabilities. It is only when the data from the two sides is brought together (which cannot happen faster than the speed of light) that the correlations become clear.
 

Polymath257

Think & Care
Staff member
Premium Member
So, you can't give a single such reference?

'An Introduction to Quantum Field Theory' by Michael Peskin and Daniel Schroeder, pages 13-15 and again 27-29. Also page 54.

Notice that causality (as defined in quantum field theories) is equivalent to locality because of relativity: anything outside of the light cone is in the past from some frame of reference.

Or, if you want,

'Elementary Particle Physics' by Otto Nachtman. On page 43, Assumption III is the assumption of locality for quantum field theories.

Edit: If you want an online version, look at
http://www.damtp.cam.ac.uk/user/tong/qft/qft.pdf
The equation at the top of page 37 is the requirement of locality: no influences travel faster than light.
 
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siti

Well-Known Member
Tell it to the physicists:
Certainly.

the physicists said:
Indeed, violations have been measured.
No they haven't! What has been measured are the electrical signals derived from the responses of a pair of photoelectric devices 'tuned' to detect the arrival of 'photons' with selected polarization properties. The selection is made in such a way that the information about what properties are selected for measurement at one station (Alice) could not be transmitted by any classical mechanical process (i.e. without propagating faster than light) to the other station (Bob). The results have shown (in a number of experiments with increasingly robust experimental set-ups designed to eliminate the possibility of undetectable classical processes - aka 'loopholes') a statistically significant correlation between the detections at Alice's detector and Bob's detector that cannot be accounted for by any so-called 'hidden variables' interpretations of quantum mechanics. Bell's Theorem says that any classically determined system (of local, realistic particles with determined properties) would predict a particular inequality between photon detections at the two detectors (i.e. that the number of detection events where the two detectors correspond compared to the number where they don't correspond would be greater than or equal to a particular fraction of the total number of detection events) as there would be no way that the polarization information could possibly be transmitted between the 'entangled' photons in time. The violations of Bell inequalities (where the detection events correspond to each other more than could be predicted by 'hidden variables') are, however, correctly predicted - but by no means fully accounted for - by the probability of quantum mechanics - i.e. the precise mechanism by which the information is shared between Alice's photons and Bob's photons remains unknown.
 

Nous

Well-Known Member
Premium Member
But it *is* local.
You have made it abundantly clear that you hold the belief that QM is a local theory. I've challenged you numerous times to prove that your claim is true, and you haven't been able to do so. Your belief has not basis in reality.
 

Polymath257

Think & Care
Staff member
Premium Member
You have made it abundantly clear that you hold the belief that QM is a local theory. I've challenged you numerous times to prove that your claim is true, and you haven't been able to do so. Your belief has not basis in reality.

Posts #284 and #294
 

Nous

Well-Known Member
Premium Member
Bell clearly states that "If [a hidden variable theory] is local it will not agree with quantum mechanics . . ."

You should work on getting more comfortable with the facts.
And quantum mechanics is not a hidden variable theory. It *is* local, bit it is not realist.
Obviously you need to clear your head of your beliefs and concentrate on what Bell said.

Apparently you are trying to knock down a straw man. Note the description of Einstein's objection to QM with which this paper begins:

Einstein never accepted orthodox quantum mechanics because he did not believe that its nonlocal collapse of the wavefunction could be real. When he first made this argument in 1927 (ref. 1), he considered just a single particle. The particle’s wavefunction was diffracted through a tiny hole so that it ‘dispersed’ over a large hemispherical area before encountering a screen of that shape covered in photographic film. Since the film only ever registers the particle at one point on the screen, orthodox quantum mechanics must postulate a ‘peculiar mechanism of action at a distance, which prevents the wave... from producing an action in two places on the screen’1. That is, according to the theory, the detection at one point must instantaneously collapse the wavefunction to nothing at all other points.​

Experimental proof of nonlocal wavefunction collapse for a single particle using homodyne measurements : Nature Communications

It's the collapse of the wavefunction that is nonlocal--even the wavefunction of a single particle, as this study demonstrates.
There is nothing non-local going on here.
Wow. You just haven't understood anything about quantum mechanics. The description of Einstein's objection to the nonlocal implications of QM seem to me to be quite clear. I don't see how anyone could fail to understand that the particle's wavefunction is expanding over a large expanse, then when it is measured, by hitting a screen, it collapses to a single point.

Even middle school students understand these ideas. You've got work to do.

Quantum mechanics is nonlocal and nonrealist:

Quantum theory predicts and experiments confirm that nature can produce correlations between distant events that are nonlocal in the sense of violating a Bell inequality [1].​

https://www.researchgate.net/profile/Antia_Lamas-Linares/publication/260176298_Testing_quantum_correlations_versus_single-particle_properties_within_Leggett'smodel_and_beyond/links/5589aec108ae4e384e25fed5/Testing-quantum-correlations-versus-single-particle-properties-within-Leggettsmodel-and-beyond.pdf

The abundant experimental confirmation of Bell’s Theorem has made a compelling case for the nonlocality of quantum mechanics (QM), in the precise sense that quantum phenomena exhibit correlations between spacelike separate measurements that are inconsistent with any common cause explanation​

https://arxiv.org/pdf/quant-ph/9906036.pdf

The above results suggest that Bob’s portion of the single photon cannot have a local quantum state before Alice defining her measurement setting θ.

Experimental proof of nonlocal wavefunction collapse for a single particle using homodyne measurements : Nature Communications

A violation of Bell’s inequality not only tells us something about quantum physics, but more impressively, tells us that some spatially separated systems exhibit nonlocal correlations. This must be true for any future theory that is put forward as a complete quantum theory. Consequently, it is nature herself that is nonlocal.​

http://www.alice.id.tue.nl/references/gisin-2009.pdf

In the [Aharonov-Casher] experiment, the invalidity of both the Bell inequality and the Leggett inequality suggests that quantum mechanics is neither local nor realistic. The result is consistent with the works in the literatures11 12 13 14 based on the experiment of entangled photons.​

Testing Leggett's Inequality Using Aharonov-Casher Effect : Scientific Reports
 
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Nous

Well-Known Member
Premium Member
'An Introduction to Quantum Field Theory' by Michael Peskin and Daniel Schroeder, pages 13-15 and again 27-29. Also page 54.

Notice that causality (as defined in quantum field theories) is equivalent to locality because of relativity: anything outside of the light cone is in the past from some frame of reference.

Or, if you want,

'Elementary Particle Physics' by Otto Nachtman. On page 43, Assumption III is the assumption of locality for quantum field theories.

Edit: If you want an online version, look at
http://www.damtp.cam.ac.uk/user/tong/qft/qft.pdf
The equation at the top of page 37 is the requirement of locality: no influences travel faster than light.
So you still can't quote even a single scholarly source claim the quantum mechanics is a local theory?

The only reason that you are unable to substantiate your claim that QM is a local theory is because your claim unequivocally false.
 

Nous

Well-Known Member
Premium Member
Indeed, violations have been measured.
No they haven't! What has been measured are the electrical signals
They detected the signals. They measured a violation of a Bell-type inequality.

The results have shown (in a number of experiments with increasingly robust experimental set-ups designed to eliminate the possibility of undetectable classical processes - aka 'loopholes') a statistically significant correlation between the detections at Alice's detector and Bob's detector that cannot be accounted for by any so-called 'hidden variables' interpretations of quantum mechanics.
No, Bell's theorem and the Bell test experiments rule out local hidden variables as a way to account for the correlations. The de Broglie-Bohm pilot wave theory is a nonlocal hidden variable theory.

The violations of Bell inequalities (where the detection events correspond to each other more than could be predicted by 'hidden variables') are, however, correctly predicted - but by no means fully accounted for - by the probability of quantum mechanics - i.e. the precise mechanism by which the information is shared between Alice's photons and Bob's photons remains unknown.
See Nicholas Gisin's Science article: Quantum Nonlocality: How Does Nature Do It?
 
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