The Refutation of Bohmian Mechanics

Demystifier

Irrespective of physics, this chain of reasoning is logically totally wrong.
Namely, if A is some evidence for B, it does not mean that A implies B.
For example, being in grave is an evidence for being dead, but you can still be in grave without being dead.

Anyway, perhaps we are a statistical fluctuation?

Demystifier

I'm not sure what kind of an answer do you expect here. Perhaps the straightest answer is: through the Schrodinger (or Schrodinger-Pauli, or Dirac, or Maxwell ...) equation and the associated equation for the particle trajectories - of the isolated system.

camboy

So, as you haven't corrected yourself at all, do I take it you don't accept that anything that you have said is wrong?

If this is not the case, would you mind listing for me the things about which you have changed your opinion as a result of this thread?
As far as deBB is concerned, you appear to be entirely ignorant of everything that has been published since the 1990s, of a great many things published before that, and of absolutely everything that refutes your and Streater's "Bohmian mechanics is demonstrably incorrect" thesis. So I feel free to make certain assumptions.
That's not my point. No-one is asking for thanks. My complaint is the following. You have made multiple statements on this thread which are demonstrably incorrect. When told they are incorrect and you apparently have no further argument, you simply move onto another point without saying whether you agree with the correction or not. Anyone reading this thread and attempting to make sense of it needs to have that information if they are to draw a conclusion about who is right and who is wrong, otherwise they might simply assume because you are a big clever person and I am a student that you automatically win. Is that your intention? Because it certainly looks like it.
Then I apologize for suggesting that you were.

EDIT: though looking at your public web page, you can hardly blame me for my assumption. So you're a professor of mathematics who has the foundations of quantum mechanics as one of his main research interests. Huge difference, I agree. My original point therefore stands that - as a respectable professor at a major university - you have a responsibility not to make sweeping incorrect statements damning entire fields in public forums, since people will believe you merely because of who you are.
Then what on earth did you mean by statements such as "The worst thing about Bohmian mechanics is their low standards of quality", "Bohmians are not aware of many things", "Bohmian trickery is inapplicable" and all the rest. Are these supposed to be compliments?

Don't misunderstand me. I am happy to debate you, but not on the understanding that you are so goddamned clever that your so-called disproof of Bohmian mechanics is so obvious it doesn't need to be peer-reviewed, or when you persist in continually using such a sarcastic tone.

akhmeteli

First, you may have noticed an emoticon by my "claim", second, strictly speaking, depending on peer reviews, truth either belongs here or not (so it is indeed "dependent" in this respect on peer reviews). With all due respect, your "truth" of post 7 does not belong here.

No, we don't have to agree. And no, the fact that your paper has been cited does not make its discussion here appropriate. Rules are rules. I am not trying to look "holier than thou". I admit that I also sinned against this rule and got a heads-up from a mentor. Since then I tried to stick to the rules.

I am sure mentors here value your input, as I do, and would give you some slack, as I would do, if I were in their shoes, but you should not abuse our respect.

And again, if indeed the Bohm interpretation is a lost cause, so be it, but I specifically objected to your claim and was not trying to defend the interpretation. To explain my position I may mention that I had a longish discussion with a knowledgeable Bohmian here. Ironically, I also argued in that discussion that there is no clear indication of discrepancy between predictions of the Bohm interpretation and standard quantum mechanics.

In your example both the Bohm interpretation and standard quantum mechanics predict the same state forever. It is not at all obvious that the Bohmian interpretation gives wrong statistics in this case (unless you impose your very own theory of measurements on the Bohm interpretation, as you do in your paper). I believe this is just your personal theory.

If this is meant to be an argument, I fail to see how it is relevant. Maybe I just don't know enough about quantum computing though. However, I did not ask you for arguments, I asked about the status of your claim "no quantum computing in the Bohm interpretation." This is another strong claim, and I just tried to understand if that was common knowledge or just another personal theory of yours. If this is common knowledge, how about a reference? And if there is no peer-reviewed article supporting your claim, then your claim does not belong here. If this is your recent discovery, please publish it first and then discuss it here.

With all due respect, this is rich. You made a strong claim, and I just challenged you to support it with valid references. I am under no obligation to prove that your claim is wrong. Furthermore, I have no idea if it is indeed wrong or right.

camboy

It is wrong. I supplied him with an appropriate reference demonstrating how to do deBB quantum computing in #22 (and again in #27 after he ignored it).

Of course he immediately dismissed it, not because of a coherent 'personal theory' but because "[deBB] can be coerced into accomodating anything - in this case by introducing artificial pointer coordinates that don't exist in the standard description". This simply means "[deBB] is not like standard QM, and I - the great Neumaier - don't like it". It is not an intellectual argument.

A. Neumaier

But in the Bohmian interpretationl, one interprets only changes in the pointer varibles as observables.. Thus the nerves won't serve as pointer variables to observe light.

A. Neumaier

If the Boltzmann's H-therorem were any evidence for the universe being in global equilibrium then
e would observe this global equilibrium - which means we wouldn't exist, contradiction.[/QUOTE]
Irrespective of physics, this chain of reasoning is logically totally wrong.
Namely, if A is some evidence for B, it does not mean that A implies B.
For example, being in grave is an evidence for being dead, but you can still be in grave without being dead.[/QUOTE]
This means that you have very weak standards for what you regard as evidence for global thermal equilibrium and for quantum equilibrium. Your arguments deon't hold any water, as my example of the hill-climber showed.
No serious statistician rregards anything as a fluctuation that persists for so long.

A. Neumaier

In standard QM, a spin system is given by N spins, basis states that tell which subset of spins is up (the complementary subset is down), their linear compinations as general statres, and a Hamiltonian that is an expression in the su(2) operators J^k_0, J^k_+ and J^k_-, one k for each spin. This determines the quantum dynamics via Schroedinger's equation i hbar psi(t)=H psi(t).

But it doesn't determine the Bohmian dynamics if there is no detector close by to give ontological meaning to the system.

A. Neumaier

Indeed. I believe that my position regarding my paper is correct. Your arguments didn't convince me of a mistake.
For example, I had thought that Bohmian mechanics never considered quantum computing, and I learnt that it had. Though the presentation given was not enough to convinve me that BM accounts for qunatum computing - see the still pending dialogue.
It may appear s to you,, but it isn't the case.
more precisely, which seem incorrect to you. I didn't buy your arguments.
In questions of interpretation, there is a lot of room for differing opinions on the same statement.
The point of a conversation on PF is not to be proved right or wrong but to provide information for readers so that they can make up their own mind. I write to contribute further information, not to justify myself.
They shouldn't take anything on authority if there are conflicting opinions. They should study the arguments of both sides and form their own picture.
If you look at my list of research interests http://www.mat.univie.ac.at/~neum/#research , you'll find that quantum mechnaics is a minor part of my research interests. About 4% of my piblications are about quantum mechanics.
I don't make sweeping incorrect statements damning entire fields. Saying that Bohmian mechnaics contradicts quantum mechnaics doesn't damn the field. Classical mechnaics also contradicts QM, but nobody thinks that this implies that whoever does rersearch in classical mechanics is an idiot. Far from this!!!
The first means, for example, that they take things such as the establishment of quantum equilibrium for the universe to be proven although they have extremely little ''evidence'' for it. The second is a truism that holds for everyone, and must be read in context. The third is a statement asserttin that the machinery of Bohmian mechanics is not applicable. Calling it trickery is clearly a subjective statement implying that BM gives an appearance of reality to QM of the same kind as a juggler makes things appear real without being so. This is a nonrefutable statement since BM say often that the motion of the quantum particles is not observable. Thus considering it as trickery is legitimate.

A. Neumaier

If you think giving a reference to an unpublished arXiv paper without discussing it is a serious sin against the rules, you should report it to the PF management, quoting the present post for context.
I fully respect the rules as I understand them.
But I cannot discuss my claim further because of the PF rules. So your objection standas like my assertion, and readers must make up their own mind.
First, I qualified my statement with ''probably'' since I wasn't sure, and indeed, there was a very recent (2010) thesis that tackled it, as was pointed out by others. I immediately acknowledged the article, studied it, and found that it didn't treat spin systems by themselves but only spin systems coupled to an external pointer variable, thus justifying my remark ''The observables used there do not include a position variable, hence the Bohmian trickery is inapplicable.''. However, I learnt that the author invented (or got from somewhere else) a new Bohmian trick - namely that one silently changes the system under study to a bigger one, in order to give it the appearance of fitting into the BM philosophy. This lead to a still ongoing discussion.
If everyone were banned who made more than 10 claims that do not appear in a peer-reviewed article, PF would be nearly empty.

Demystifier

No, that's not true. I never said that.

Demystifier

That's correct.

You are wrong. Bohmian dynamics is well defined and gives an ontology even without detectors. But in that case, the statistical predictions may differ from those of ordinary QM. Yet, there is no conflict with experiments because these deviations from ordinary QM cannot be detected (because there are no detectors).

What is true in that case is that there is no any meaningful SPIN ontology. Still, there is some ontology in terms of a wave function and particle positions.

Let me repeat the analogy with classical optics. Colors do not exist, except for the observers. Yet, light waves exist irrespective of the observers.
Similarly, in BM spins do not exist, except for the observers. Yet, wave functions and particle positions exist irrespective of the observers.

Demystifier

That is an incorrect interpretation of BM. Just the opposite, the motion of the quantum particle is the only observable thing in BM. However, in order to observe it in practice, one must couple it with a macroscopic apparatus containing a large number of the degrees of freedom. Such a large number of degrees of freedom cannot be controlled on a fine level, which means that one cannot know the exact position-dependent phases of the wave functions involved. Without knowing the phases, one cannot predict the exact particle trajectories either. Therefore, one cannot experimentally confirm (or refute) that the measured trajectories coincide with those predicted by the theory.

A. Neumaier

You just repeated it:

A. Neumaier

Then please give me the dynamics of the unobserved spin system that I described in terms of standard QM in terms of BM.

A. Neumaier

But this means (by any meaningful interpretation of the term ''observe'') that one cannot observe the particle position but only the pointer position of the macroscopic apparatus.

Demystifier

Yes, but this macroscopic apparatus also consists of particles. So one does measure the particle positions, but of the apparatus. Not because the apparatus is fundamentally different, but simply because it is bigger.