Questions on Entanglement and Double-Slit Experiment

[ttn]

I disagree. When I say "classical mechanics", I do not need to specify if I'm talking about Newton's Laws, or Lagrangian/Hamiltonian mechanics. Yet, these two are very different approaches to solving the dynamical system. In the end, they are solving the same thing. So to me, they are "classical mechanics" mathematical formalism.

I use the same thing when talking about "quantum mechanics". I don't have to specify if I'm talking about Schrodinger Equation, matrix mechanics, Feynman path integral, Second Quantization, etc... etc. I'm not doing anything different by solving it using second quantization versus matrix mechanics.

I do not want to go into MWI and Bohm theory AGAIN! It has been talked to death. I will simply point out to you that when we have actual problems to solve beyond JUST basic QM issues, we resort back to STANDARD QM. I'll ask you to point out a single condensed matter, nuclear physics, atomic physics, etc paper that make use of non-standard QM formalism. Till that happens, we ALL know what is meant when I say "standard QM", don't we?

Or do I need to be explictly clear EVERY time we tackle and make use of the name "quantum mechanics"?

Zz.

I pointed out that the different interpretations don't all share the same formalism. I gather that your first paragraph is meant to express disagreement with that claim. But then I'm at a loss to understand what you think the issue is that you're addressing in the later paragraphs. If, according to you, Copenhagen, MWI, Bohm, GRW, etc., are all just different touchy feely ways of looking at the same exact formalism, there wouldn't even be any *difference* between solving some condensed matter problem using "standard QM" and solving it using Bohm or whatever.

You can't have it both ways. Either you define things in such a way that these are really all just the same theory (in which case it's hardly rational to be so adamantly in favor of one of them and so adamantly against the others), or you define things in such a way that these are really distinct theories (in which case it's hardly rational to support one merely because lots of people use it, in spite of the fact that others make the same predictions and are actually superior qua physics theories).

 

[JesseM]

I agree that one must know the formalism to profitably approach foundational questions. But it's definitely not true that different interpretations are merely different words or feelings about the same exact set of equations. Indeed, more precise language would be to think of the different versions of QM as distinct *theories* which give different accounts of what happens physically, contain different dynamical equations, and (in some cases) make subtly different predictions for what will be observed. Of course, the reason these are still considered viable is that they all make the same predictions for what should be observed in the kinds of cases that have actually been examined experimentally.

In what situations do they "make subtly different predictions for what will be observed"? I thought they all made identical predictions for the results of all possible measurements, which is why they are called "interpretations" and not "theories".

 

[ZapperZ]

I pointed out that the different interpretations don't all share the same formalism. I gather that your first paragraph is meant to express disagreement with that claim. But then I'm at a loss to understand what you think the issue is that you're addressing in the later paragraphs. If, according to you, Copenhagen, MWI, Bohm, GRW, etc., are all just different touchy feely ways of looking at the same exact formalism, there wouldn't even be any *difference* between solving some condensed matter problem using "standard QM" and solving it using Bohm or whatever.

You can't have it both ways. Either you define things in such a way that these are really all just the same theory (in which case it's hardly rational to be so adamantly in favor of one of them and so adamantly against the others), or you define things in such a way that these are really distinct theories (in which case it's hardly rational to support one merely because lots of people use it, in spite of the fact that others make the same predictions and are actually superior qua physics theories).

But you can't have it both ways either.

If you claim that they ARE different, both philosophically AND in their formalism, then the "others" have a major stumbling block in the sense that they are NOT being used at all in high-degree-of-certainty fields such as condensed matter. Point out to me a condensed matter paper that do make use of MWI formalism if you claim it is distinctly different than the standard QM. You'll find NONE.

If you claim that they are the same, then what are we arguing about?

This is going OFF TOPIC. You have had your chance, plenty of it, to do this in other threads. You should not need such flimsy excuse to continue this here.

Zz.

 

[ttn]

But you can't have it both ways either.

If you claim that they ARE different, both philosophically AND in their formalism, then the "others" have a major stumbling block in the sense that they are NOT being used at all in high-degree-of-certainty fields such as condensed matter. Point out to me a condensed matter paper that do make use of MWI formalism if you claim it is distinctly different than the standard QM. You'll find NONE.

If you claim that they are the same, then what are we arguing about?

This is going OFF TOPIC. You have had your chance, plenty of it, to do this in other threads. You should not need such flimsy excuse to continue this here.

Zz.

Fine, I don't want to pursue it either. I just wanted to point out the error in your statement that different versions of QM all share the same formalism. That isn't true, and I'll leave it at that.

 

[ZapperZ]

Fine, I don't want to pursue it either. I just wanted to point out the error in your statement that different versions of QM all share the same formalism. That isn't true, and I'll leave it at that.

Then they are NOT the "QM" that you think I was referring to, because, whoa, they are NOT used in any practical aspect that require them to be CORRECT before they can be used in utmost confidence.[1]

How about them apples?

Zz.

[1] D.F. Styer et al. Am. J. Phys. v.70, 288 (2002).

 

[ttn]

Then they are NOT the "QM" that you think I was referring to, because, whoa, they are NOT used in any practical aspect that require them to be CORRECT before they can be used in utmost confidence.[1]

How about them apples?

Zz.

[1] D.F. Styer et al. Am. J. Phys. v.70, 288 (2002).

So you're saying the different formulations actually make different predictions for what should happen in your precious condensed matter experiment? That, because their formalisms differ from "standard QM", they are not "CORRECT", and that this is why condensed matter physicists don't use them?

If so you're an illiterate idiot. Come down off your high horse and actually learn what you're talking about. You might start by reading from the abstract of the paper you tried to throw in my face:

"The various formulations differ dramatically in mathematical and conceptual overview, yet each one makes identical predictions for all experimental results."

(This, however, is not an endorsement of the papers of Styer et al's foundational papers. Their "common misconceptions" paper is notoriously full of ... misconceptions ... about things like Bell's theorem.)

 

[ZapperZ]

So you're saying the different formulations actually make different predictions for what should happen in your precious condensed matter experiment? That, because their formalisms differ from "standard QM", they are not "CORRECT", and that this is why condensed matter physicists don't use them?

I said NOTHING of that sort. You were the one who claimed that they are different! And who said anything about "condensed matter EXPERIMENT"? You don't think there's any "theoretical" work in condensed matter at all? Try looking at a few papers and point out to me where non-standard QM that isn't part of Styer's paper have ever been used? Why? Because the formulation hasn't been tested to the most rigorous extent as to be USED with utmost confidence. Nowhere in any theoretical description of ANY condensed matter systems are there any usage of non-standard QM. This last part is not an opinion, whether you like it or not.

If so you're an illiterate idiot. Come down off your high horse and actually learn what you're talking about. You might start by reading from the abstract of the paper you tried to throw in my face:

"The various formulations differ dramatically in mathematical and conceptual overview, yet each one makes identical predictions for all experimental results."

But that is what I've been trying to say from the very beginning! It is why I brought up the different approaches in classical mechanics. The different formulations of QM are not "different QM", the same way Newton Laws are not different classical mechanics from Lagrangian/Hamiltonian mechanics! You were the one who indicated that they produce "subtly DIFFERENT predictions"!

(This, however, is not an endorsement of the papers of Styer et al's foundational papers. Their "common misconceptions" paper is notoriously full of ... misconceptions ... about things like Bell's theorem.)

Talk is cheap. I see that you didn't write any rebuttal to that paper that they have published. Why is it that whenever there is a published paper that someone finds something "wrong", the best he/she can do is diss about it on some place like this, rather than staking one's reputation and write a rebuttal?

[I will overlook your personal attack on me this time. However, unless you wish for this thread to go down the gutter, I will onlywarn you just once to cease resorting to such thing.]

Zz.

 

[Careful]

Nowhere in any theoretical description of ANY condensed matter systems are there any usage of non-standard QM. This last part is not an opinion, whether you like it or not.

The reason why, Zapper, is that it would be far too complex to calculate for example the Bohmian trajectories of cooper pairs in a superconductor; if you ever tried to do something far easier than this, then you would figure out that this is a fairly obvious reason.

But that is what I've been trying to say from the very beginning! It is why I brought up the different approaches in classical mechanics. The different formulations of QM are not "different QM", the same way Newton Laws are not different classical mechanics from Lagrangian/Hamiltonian mechanics! You were the one who indicated that they produce "subtly DIFFERENT predictions"!

Newtonian mechanics is not equivalent to the Lagrangian formalism, eg. not every force equation can be written as the Euler Lagrange equation for some Lagrangian.

Talk is cheap. I see that you didn't write any rebuttal to that paper that they have published. Why is it that whenever there is a published paper that someone finds something "wrong", the best he/she can do is diss about it on some place like this, rather than staking one's reputation and write a rebuttal?

Even though you did not ask this question to me, I will answer that one. First, if one were to write rebuttals against every rubbish paper that is published on the arxiv, that would be more than a fulltime job. Second, you continue to confuse ``talk'' with argumented opposition, a forum like this seems perfectly suited for the latter.

Careful

 

[ZapperZ]

The reason why, Zapper, is that it would be far too complex to calculate for example the Bohmian trajectories of cooper pairs in a superconductor; if you ever tried to do something far easier than this, then you would figure out that this is a fairly obvious reason.

So forget about "cooper pairs in a semiconductor". Use it to do something a lot simpler, like deriving the Landau Fermi Liquid model!

I'm not arguing if it is easy or not, or possible or not. I'm arguing that in the literature, no where are any of these so-touted formalism are ever used in condensed matter, plasma physics, atomic/molecular physics, etc... etc... i.e. all the subject area in which QM is used as an APPLICATION. This lack of usage seems to be completely ignored in any of the argument touting their strength. It's like a 3000 lb gorrilla that no one seems to talk about. Or maybe it is because one looks down on such "applied fields" that they bare no importance whatsoever in considering the validity of such description? And *I* am the one who is on some "high horse"?

Newtonian mechanics is not equivalent to the Lagrangian formalism, eg. not every force equation can be written as the Euler Lagrange equation for some Lagrangian.

Eh?

In principle, for every equation of motion that one solves with the Newtonian mechanics, one would get the identical equation of motion using Lagrangian/Hamiltonian mechanics. You are welcome to show me an example where it doesn't. There are no "subtle difference" in the outcome of each approach as far as the final result is concerned.

Even though you did not ask this question to me, I will answer that one. First, if one were to write rebuttals against every rubbish paper that is published on the arxiv, that would be more than a fulltime job. Second, you continue to confuse ``talk'' with argumented opposition, a forum like this seems perfectly suited for the latter.

Careful

I never care about rebuttals for anything appearing on ArXiv. That's absured considering that I do not consider such format as a peer-reviewed medium. It is why I gave the complete published citation to Styer's paper. So send a rebuttal to AJP. And no, this forum is NOT suited for such idle comments like that when one cannot make a valid supporting argument. We require that people to base their arguments on valid physics, and that requires supporting documents. Saying Styer's paper is itself full of misconception says NOTHING, because that is a superficial statement with zero explanation and documentation. If one truly has a valid argument, then I'd rather see it being published as a rebuttal, and see how Styer and the rest of the physics community respond to that. That is how physics is done, NOT in open forums such as this, especially when there's a conflict of opinion!

Now I KNOW for certain that someone is going to come up and accuse me of trying to stop all "questioning" of current ideas. I will put it to you that that is not even close to what I'm asking. However, and you know who you are, there are people who are adamant in pushing whatever it is they're pushing that somehow the rest of us who continue to use the standard formalism are ignorant and stupid. To me, it is obvious that these people have already made up their minds and decisions, and thus, know that they are correct. I want them to put their money where their mouths are. Stop dissing this and that, and go put your reputation on the line. For once, do something that counts rather than just wasing your valuble talent on an open forum that will do nothing to enhance your standing as a physicist (or whatever it is that you are choosing to be). There are TONS of published papers that clearly disagree with whatever it is you're pushing. Send rebuttals! Can't do for all of them, try 2, 3, 4... etc. Pick the most important ones, the ones that a lot of people are citing in some prestigious journals. Go burst that big bubble! Go on! I dare you!

Zz.

 

[DrChinese]

First, if one were to write rebuttals against every rubbish paper that is published on the arxiv, that would be more than a fulltime job.

Be fair: ZapperZ's reference was not one from the arxiv.

D.F. Styer et al. Am. J. Phys. v.70, 288 (2002)

At this point, alternative interpretations are NOT making any testable predictions involving their different "formalisms". In fact, it seems to me more the opposite. They lay the groundwork to prove that they do reduce to the QM formalism so they at least get a chance to be taken seriously.

And this makes perfect sense, considering the experimental validation of QM to date.

 

[Careful]

So forget about "cooper pairs in a semiconductor". Use it to do something a lot simpler, like deriving the Landau Fermi Liquid model!

I'm not arguing if it is easy or not, or possible or not. I'm arguing that in the literature, no where are any of these so-touted formalism are ever used in condensed matter, plasma physics, atomic/molecular physics, etc... etc... i.e. all the subject area in which QM is used as an APPLICATION.

Right, and the reason is that this would be way too difficult : I recall you the recent paper I referred you to about atomic transitions of electrons in BM for the H atom.

Eh?

In principle, for every equation of motion that one solves with the Newtonian mechanics, one would get the identical equation of motion using Lagrangian/Hamiltonian mechanics. You are welcome to show me an example where it doesn't. There are no "subtle difference" in the outcome of each approach as far as the final result is concerned.

Look again at the conditions on the force function in d'Alembert's derivation of the Euler Lagrange equation from Newton's second law. For suitable force functions (eg. conservative force fields), both appraoches agree of course ... (the restriction obviously is that you cannot play the trick of increasing the number of dynamical variables, or add Lagrange multipliers or so... ).

Saying Styer's paper is itself full of misconception says NOTHING, because that is a superficial statement with zero explanation and documentation. If one truly has a valid argument, then I'd rather see it being published as a rebuttal, and see how Styer and the rest of the physics community respond to that. That is how physics is done, NOT in open forums such as this, especially when there's a conflict of opinion!

I did not read this paper, neither did I read the comments offered by ttn; it was just a general remark based upon the assumption that ttn had done his homework.

I want them to put their money where their mouths are. Stop dissing this and that, and go put your reputation on the line. For once, do something that counts rather than just wasing your valuble talent on an open forum that will do nothing to enhance your standing as a physicist (or whatever it is that you are choosing to be). .

The reason for me to be on this forum from time to time is my own business. And yes, I am still working on QM and making some progress recently ; only I do know very well how hard it is to do something truly original and *useful* on such a longstanding problem. As I once said, it is not difficult at all to think of local realist scenario's behind entanglement (holography, extra dimensions and so on), but it is damn difficult to find a plausible one !

Cheers,

Careful

 

[ZapperZ]

Right, and the reason is that this would be way too difficult : I recall you the recent paper I referred you to about atomic transitions of electrons in BM for the H atom.

Is it really?

If you look at the stuff listed in Styer's papers, at some stage, some area of physics makes use of a particular formalism. I have seen the standard "Schrodinger" method, the Heisenberg matrix method, density matrix, path integral, variational method, second quantization, etc... etc. In other words, at some point, one of these approaches were used in condensed matter, atomic/molecular physics, nuclear physics, particle physics, etc... I would think it would raise a lot of eyebrows if a particular technique is (i) "too hard" and (ii) isn't missed at all such that it isn't used in the applied field. I mean, with such variety of applications and usage, there's not even ONE single area in which such formalism would be the least bit useful to be used? What one has "invented" then is something that is utterly useless other than to make someone's philosophical view of the world better. It sounds like something that would qualify for an Ig Nobel.

Zz.

 

[Careful]

Is it really?

If you look at the stuff listed in Styer's papers, at some stage, some area of physics makes use of a particular formalism. I have seen the standard "Schrodinger" method, the Heisenberg matrix method, density matrix, path integral, variational method, second quantization, etc... etc. In other words, at some point, one of these approaches were used in condensed matter, atomic/molecular physics, nuclear physics, particle physics, etc... I would think it would raise a lot of eyebrows if a particular technique is (i) "too hard" and (ii) isn't missed at all such that it isn't used in the applied field. I mean, with such variety of applications and usage, there's not even ONE single area in which such formalism would be the least bit useful to be used? What one has "invented" then is something that is utterly useless other than to make someone's philosophical view of the world better. It sounds like something that would qualify for an Ig Nobel.
Zz.

First, you know very well that in order to compute the trajectories, one would first need to solve the full dynamical problem (since as far as I remember these trajectories show chaotic behavior), which is very hard to do even just for a system of radiating electrons. Second, I have always agreed with the statement that as far as I am concerned all popular existing alternatives to standard QM such as MWI, BM are window dressing as they stand now, so yes I can also imagine from that point of view why people did not care so much. There are exceptions such as the work of Adler and GRW, but these are all explicitely nonlocal, Barut self field is for now the only local exception, but it isn't QFT. However, a good local realist theory behind QM would for sure be useful for quantum gravity and for the sake of understanding physics. However, I doubt it would be useful for computations in condensed matter physics; likewise we do not use deterministic microphysics when dealing with macroscopic systems, we have thermodynamics for that.

Careful

 

[ttn]

What one has "invented" then is something that is utterly useless other than to make someone's philosophical view of the world better. It sounds like something that would qualify for an Ig Nobel.

Zz.

You're talking about Bohmian Mechanics here, right? You truly don't get it. Bohmian Mechanics and orthodox QM make identical predictions (at least in cases where the predictions of the latter are unambiguous). So it begs the question to just dismiss Bohm's theory as you do here. One could equally well dismiss orthodox QM (i.e., all the idiotic philosophical ramblings of Bohr) on the same basis -- namely, that what Copenhagen adds to the rigorous formulation of the pilot wave approach is just a bunch of used-to-be-trendy positivist, anti-realist, existentialist-motivated philosophical mumbo jumbo whose only function is to make some moron feel better about their anti-scientific philosophical view of the world. If you actually have any serious interest in this issue, you might start by reading Jim Cushing's book "Quantum Mechanics: Historical Contingency and the Copenhagen Hegemony". Or if you don't have any serious interest, maybe you shouldn't discuss them in public.

As to your big challenge that I should publish a rebuttal to Styer's "misconceptions" paper, see section IV of

http://puhep1.princeton.edu/~mcdonald/examples/QM/norsen_ajp_73_164_05.pdf

This is all particularly ironic given the following:

http://tech.groups.yahoo.com/group/undernetphysics/message/857

 

[JesseM]

You're talking about Bohmian Mechanics here, right? You truly don't get it. Bohmian Mechanics and orthodox QM make identical predictions (at least in cases where the predictions of the latter are unambiguous). So it begs the question to just dismiss Bohm's theory as you do here. One could equally well dismiss orthodox QM (i.e., all the idiotic philosophical ramblings of Bohr) on the same basis

They aren't really comparable, at least not if "orthodox QM" is taken to mean the ordinary shut-up-and-calculate version (which is basically what the purely positivist version of the Copehagen interpretation is, although some people use 'Copehagen interpretation' to mean the view that the collapse of the wavefunction is a real physical event), which is just a recipe for making predictions about probabilities without any assumptions (one way or another) about hidden variables, other worlds, or any other aspect of reality that can't be tested directly. Of course, you could also use the formalism of Bohmian mechanics as a recipe for making predictions, without any assumptions about the "reality" of hidden variables or the pilot wave, but this isn't what people usually mean by Bohmian mechanics.

 

[ZapperZ]

You're talking about Bohmian Mechanics here, right? You truly don't get it. Bohmian Mechanics and orthodox QM make identical predictions (at least in cases where the predictions of the latter are unambiguous). So it begs the question to just dismiss Bohm's theory as you do here. One could equally well dismiss orthodox QM (i.e., all the idiotic philosophical ramblings of Bohr) on the same basis -- namely, that what Copenhagen adds to the rigorous formulation of the pilot wave approach is just a bunch of used-to-be-trendy positivist, anti-realist, existentialist-motivated philosophical mumbo jumbo whose only function is to make some moron feel better about their anti-scientific philosophical view of the world. If you actually have any serious interest in this issue, you might start by reading Jim Cushing's book "Quantum Mechanics: Historical Contingency and the Copenhagen Hegemony". Or if you don't have any serious interest, maybe you shouldn't discuss them in public.

As to your big challenge that I should publish a rebuttal to Styer's "misconceptions" paper, see section IV of

http://puhep1.princeton.edu/~mcdonald/examples/QM/norsen_ajp_73_164_05.pdf

This is all particularly ironic given the following:

http://tech.groups.yahoo.com/group/undernetphysics/message/857

Who said anything about Bohmian Mechanics in particular? In fact, this IS included in Styer's text.

Again, it is YOU who said that there ARE formulations that make subtle difference in predictions. Bohmian mechanics does this? Yes? No? If it makes "identical predictions", then why are you up in arms here with this one? It is obviously not what YOU included in your original claim. Yet, you're picking it as an example. So you're right, I DON'T get it.

And thank you for your reference. Unfortunately, your paper has more of a problem with Bell's theorem in general rather than Styer's paper itself! You are claiming that Styer didn't have the "misconception", but rather the whole of quantum mechanics community is the one that did. And yes, I thought it was a good paper because it does present a "historical account" of a thought experiment that has been overlooked. That was it, which was essentially what I said when I pointed it out, no?

[BTW, this also falsifies the often-made claim that I only advertize papers that do not challenge the conventional ideas, even when *I* myself don't think is convincing]

Zz.

 

[ttn]

Who said anything about Bohmian Mechanics in particular? In fact, this IS included in Styer's text.

Funny, since he claims in his earlier paper that Bell's Theorem proves it can't exist.

Again, it is YOU who said that there ARE formulations that make subtle difference in predictions.

There are. GRW for example.

Bohmian mechanics does this? Yes? No?

No, as I said in the previous post, Bohm's theory makes the same predictions as orthodox QM wherever the latter is unambiguous.

If it makes "identical predictions", then why are you up in arms here with this one? It is obviously not what YOU included in your original claim. Yet, you're picking it as an example. So you're right, I DON'T get it.

My original claim was that the different versions of QM don't share the same formalism. You keep trying to twist things around and change the subject in order to win this argument. I frankly don't care about who wins; I just wanted to convey to all the reasonable people who read this that they needn't be bullied by your arrogant dismissiveness about foundational questions. I think I've achieved that, and there's no point continuing to argue about whether my "original claim" was true, so the last word is yours.

And thank you for your reference. Unfortunately, your paper has more of a problem with Bell's theorem in general rather than Styer's paper itself! You are claiming that Styer didn't have the "misconception", but rather the whole of quantum mechanics community is the one that did.

Those aren't exactly mutually exclusive. Styer was simply repeating, without real understanding, a misconception that is widely held in the physics community. Does it somehow invalidate my claim because it is targeted more widely than Styer's paper in particular? That makes no sense -- unless your goal is to follow any path, no matter how ridiculous, in order to try to win an argument.

 

[ZapperZ]

Funny, since he claims in his earlier paper that Bell's Theorem proves it can't exist.

There are. GRW for example.
No, as I said in the previous post, Bohm's theory makes the same predictions as orthodox QM wherever the latter is unambiguous.

My original claim was that the different versions of QM don't share the same formalism. You keep trying to twist things around and change the subject in order to win this argument. I frankly don't care about who wins; I just wanted to convey to all the reasonable people who read this that they needn't be bullied by your arrogant dismissiveness about foundational questions. I think I've achieved that, and there's no point continuing to argue about whether my "original claim" was true, so the last word is yours.

Those aren't exactly mutually exclusive. Styer was simply repeating, without real understanding, a misconception that is widely held in the physics community. Does it somehow invalidate my claim because it is targeted more widely than Styer's paper in particular? That makes no sense -- unless your goal is to follow any path, no matter how ridiculous, in order to try to win an argument.

No I'm not, because this thing has become so convoluted, I doubt if anyone else reading this even CARE who said what when.

My original point was, in case you forgot, that the different formulations of QM are simply variations to the SAME set of principles in the SAME way that Newtonian and Lagrangian/Hamiltonian mechanics are in classical mechanics. They may have different approaches and different "philosophical" views, but no one would call them as different classical mechanics. The list provide by Styer is a clear example where different formalism of QM essentially ARE what we ALL call "quantum mechanics" in the standard sense. My evidence? Other than Bohmian mechanics (which is nothing more than QM with an "action"), all those formulations one encounters either in textbooks, or used in various "applications". None of them produce any results that contradict each other. I don't know why this is such a sticky point!

Now you, however, decided to include what I would call non-standard QM and not only that, claim that one can also arrive and a different result using these. So by bastardizing and redefining what I said, you claim that I made a mistake in judgement. I really don't care if you have an affinity to one thing versus the other, but even YOU can see the absurdity if I have to defend something that I never claim. I never brought up bohmian mechanics till you somehow interpreted my claim as referring to it. I never make any claim about non-standard QM until you decided to claim that I did. The FACT that I repeatedly refer to what is being used in the application of QM as a measuring stick of a very mature formalism of QM somehow, according to you, is my "high horse" position. What ELSE is there, as an evidence, for something to be so well-known and well-accepted other than being used for applications?! For some odd reason, you took offense at this!

We ALL know the formalisms being used often and repeatedly in solving problems in physics beyond JUST the field of foundational QM. I cited the FACT that NO papers, theoretical or experimental, that use the non-standard formalism for problem solving/application as evidence that such formalism is still not fully matured nor accepted YET. This ISN'T a criticism of the formalism! As someone who cares more about how to get to the final result, I cannot trust something new and untested to solve my problem when it isn't part of what I care about. Why is this causing you such a problem?

BTW, are you preparing the possible rebuttal to Marcella's preprint?
http://arxiv.org/abs/quant-ph/0606141

.. and I must have missed your response to Shimony's counter argument against' your paper.
A. Shimony AJP 73, 177 (2005).

Zz.

 

[ttn]

No I'm not, because this thing has become so convoluted, I doubt if anyone else reading this even CARE who said what when.

My original point was, in case you forgot, that the different formulations of QM are simply variations to the SAME set of principles in the SAME way that Newtonian and Lagrangian/Hamiltonian mechanics are in classical mechanics. They may have different approaches and different "philosophical" views, but no one would call them as different classical mechanics. The list provide by Styer is a clear example where different formalism of QM essentially ARE what we ALL call "quantum mechanics" in the standard sense. My evidence? Other than Bohmian mechanics (which is nothing more than QM with an "action"), all those formulations one encounters either in textbooks, or used in various "applications". None of them produce any results that contradict each other. I don't know why this is such a sticky point!

Now you, however, decided to include what I would call non-standard QM and not only that, claim that one can also arrive and a different result using these. So by bastardizing and redefining what I said, you claim that I made a mistake in judgement. I really don't care if you have an affinity to one thing versus the other, but even YOU can see the absurdity if I have to defend something that I never claim. I never brought up bohmian mechanics till you somehow interpreted my claim as referring to it. I never make any claim about non-standard QM until you decided to claim that I did. The FACT that I repeatedly refer to what is being used in the application of QM as a measuring stick of a very mature formalism of QM somehow, according to you, is my "high horse" position. What ELSE is there, as an evidence, for something to be so well-known and well-accepted other than being used for applications?! For some odd reason, you took offense at this!

We ALL know the formalisms being used often and repeatedly in solving problems in physics beyond JUST the field of foundational QM. I cited the FACT that NO papers, theoretical or experimental, that use the non-standard formalism for problem solving/application as evidence that such formalism is still not fully matured nor accepted YET. This ISN'T a criticism of the formalism! As someone who cares more about how to get to the final result, I cannot trust something new and untested to solve my problem when it isn't part of what I care about. Why is this causing you such a problem?

Since I promised to give you the last word, I won't respond to this part.

But I will answer the questions you posed:

BTW, are you preparing the possible rebuttal to Marcella's preprint?
http://arxiv.org/abs/quant-ph/0606141

.. and I must have missed your response to Shimony's counter argument against' your paper.
A. Shimony AJP 73, 177 (2005).

If you really want to discuss this topic -- i.e., the validity of the Einstein's Boxes argument for the incompleteness/nonlocality dilemma faced by orthodox QM -- I would be happy to oblige. Why don't you start a new thread and we'll just wipe the slate clean and focus on this topic?

But to answer the specific questions: no, I am not preparing a rebuttal to that paper of Marcella, since it is very poorly done. (He doesn't even understand what the argument is he thinks he's rebutting.) And, for what it's worth, the same is true of Shimony's piece. I would be happy to elaborate further in the other thread if you're interested in discussing it. Maybe you could get the discussion going by briefly summarizing your own objections to the arguments I made in the paper (you suggested before that you didn't find it convincing) and then summarize the alleged rebuttals of Shimony and Marcella and explain why you agree with those (if you do).

 

[ZapperZ]

But to answer the specific questions: no, I am not preparing a rebuttal to that paper of Marcella, since it is very poorly done. (He doesn't even understand what the argument is he thinks he's rebutting.) And, for what it's worth, the same is true of Shimony's piece. I would be happy to elaborate further in the other thread if you're interested in discussing it. Maybe you could get the discussion going by briefly summarizing your own objections to the arguments I made in the paper (you suggested before that you didn't find it convincing) and then summarize the alleged rebuttals of Shimony and Marcella and explain why you agree with those (if you do).

No, I'm not trying to get in the "last word" here, but I want to make an important clarification.

No where in here did I objected to your arguments. Remember what brought this about. You accused Styer's paper as being full of misconception. That was what I questioned. You tried to support my question by producing your paper. I brought up others that also questioned yours.

What was my point in doing this? It is to show you that what you believe to be a "misconception", others find that YOUR work to also be that, a misconception. At some point, till this is worked out, it becomes as matter of opinion.

This is also EXACTLY my point in why we (as in those of us who have to QM to solve things, and NOT just study the "fundamental" aspect of it) will stick to the standard QM, because we know that works! I know you probably put very little importance to such a concept, but the reality is, if people's lives depend on us getting it right, we have to stick to what we know works. I find no higher degree of validity than that. I use that as a test of ANY theories out there.

Zz.

 

[DrChinese]

You're talking about Bohmian Mechanics here, right? ...One could equally well dismiss orthodox QM (i.e., all the idiotic philosophical ramblings of Bohr) on the same basis...

While you are busy trying to diss QM with an ad hominem attack on Bohr, you might consider balancing the equation with some of Bohm's equivalent jewels. "Wholeness and the Implicate Order", perhaps?

Just a minor comment: your genuinely thought provoking ideas are much more cleanly presented when you skip the gratuitous insults.

Besides, if Bohmian Mechanics had come first and paved the way, then PERHAPS the conversation would be reversed. No one gets much credit for being the second to discover something. At this point, it has been about 50 years and we still have nothing novel from this interpretation (BM that is) that I am aware of. But you never know, perhaps the big validation is right around the corner.

 

[ttn]

What was my point in doing this? It is to show you that what you believe to be a "misconception", others find that YOUR work to also be that, a misconception. At some point, till this is worked out, it becomes as matter of opinion.

Well, like I said, I would be delighted to actually work it out in discussion with you. If you're interested, start a thread (so we don't hijack this one any more than we already have).

This is also EXACTLY my point in why we (as in those of us who have to QM to solve things, and NOT just study the "fundamental" aspect of it) will stick to the standard QM, because we know that works! I know you probably put very little importance to such a concept, but the reality is, if people's lives depend on us getting it right, we have to stick to what we know works. I find no higher degree of validity than that. I use that as a test of ANY theories out there.

I don't disagree with any of that. But if you think we can be sure that Copenhagen QM "works", but we aren't or can't presently be sure whether Bohmian Mechanics "works", you still haven't understood what is at issue here. Perhaps that point will come out into the light if we take this up in another thread.

 

[ttn]

While you are busy trying to diss QM with an ad hominem attack on Bohr, you might consider balancing the equation with some of Bohm's equivalent jewels. "Wholeness and the Implicate Order", perhaps?

Yup, Bohm was a loony in his later years. But, like you, I don't think this is relevant. My point wasn't to argue for Bohm by dissing Bohr with some kind of ad hominem. My point was just that any argument of the form "Copenhagen is great because it works, while Bohm just muddies and encumbers things with his pet philosophical bias" is invalid -- because it can trivially be turned around. What actually matters is, as ZZ has said, whether or not a theory "works" -- i.e., whether it makes the right predictions and satisfies time-tested standards for what constitutes a good scientific theory (e.g., that its formulation be clear and precise and its predictions unambiguous).

Besides, if Bohmian Mechanics had come first and paved the way, then PERHAPS the conversation would be reversed. No one gets much credit for being the second to discover something. At this point, it has been about 50 years and we still have nothing novel from this interpretation (BM that is) that I am aware of. But you never know, perhaps the big validation is right around the corner.

Several points here. First, in a very real sense, Bohmian Mechanics *did* come first. De Broglie discovered it before the full orthodox Copenhagen theory was worked out, but (unfortunately) abandoned the ideas in the face of tremendous negative peer pressure from the Copenhagen crowd. See

http://www.arxiv.org/abs/quant-ph/0609184

for an extremely eye-opening, book-length treatment. And by the way, this is quite important because it establishes rather clearly that it *was* philosophical bias which made the community reject the deterministic pilot-wave theory in favor of what emerged as orthodox QM. Which shows the preposterousness of the kind of argument I mentioned above (that one should just accept Copenhagen as a good scientific theory purely on the grounds that it "got its foot in the door", and then reject any alternatives on principle as just "mumbo jumbo motivated by philosophical bias" or whatever).

Second, it's not clear what you mean by "the big validation". Do you mean some experimental result which shows Bohm's theory to be true and Copenhagen to be false? That's not likely since they basically make the same predictions. Of course, you'll want to respond: aha, that just shows that Bohm's theory doesn't add anything new, and so shouldn't be considered. But you see, that's based on the unjustified taking of Copenhagen as somehow better merely because of the foot-in-the-door point. To whatever extent it's really true that Bohm and Copenhagen make identical predictions, there can be no valid argument that some experiment (or lack thereof) is a special problem for one of the theories and/or a reason for support of the other.

Third, you suggest that nothing useful or important has ever come of Bohm's version of quantum theory. But that's definitely wrong. "The most profound discovery of science" (Stapp's description of Bell's Theorem) was directly motivated by Bell's discovery (more than a decade after Bohm published his theory in 1952, and hence several decades after de Broglie had originally advocated the theory) that Bohm had "done the impossible" -- i.e., provided a direct explicit counterexample to von Neumann's so-called "proof" that one couldn't understand the quantum predictions as arising from a normal, causal, underlying physical process. You should actually read what Bell says and does, instead of accepting as gospel the misconceptions of people like Styer (who, remember, claimed that Bell's theorem actually *refutes* the possibility of a theory like Bohm's... quite a miconception since in fact it was Bell's stumbling onto the really-existing Bohm theory that led him to the famous theorem).

 

[JesseM]

Yup, Bohm was a loony in his later years. But, like you, I don't think this is relevant. My point wasn't to argue for Bohm by dissing Bohr with some kind of ad hominem. My point was just that any argument of the form "Copenhagen is great because it works, while Bohm just muddies and encumbers things with his pet philosophical bias" is invalid -- because it can trivially be turned around.

Do you have a response to my counterargument above, then? Again, "Copenhagen" in the logical-positivist sense and not the "wavefunction collapse is real" sense is basically just the shut-up-and-calculate interpretation, and as such you can't turn it around, because this "interpretation" makes no assumptions one way or another about the existence of any physical realities which can't be measured directly, while Bohm's interpretation does.

 

[Careful]

Several points here. First, in a very real sense, Bohmian Mechanics *did* come first. De Broglie discovered it before the full orthodox Copenhagen theory was worked out, but (unfortunately) abandoned the ideas in the face of tremendous negative peer pressure from the Copenhagen crowd.

True, de Broglies theory was even more complicated than Bohm's (actually you could say that Bohm did not do his homework of crosschecking the literature properly). But de Broglie remained in favor of locality for his entire life and would never have agreed with Bohm's opinions about nonlocality. In that context he remarked that accepting Bell's theorem as an absolute truth testified of a lack of imagination - something I deeply agree with.

 

[ttn]

They [i.e., orthodoxy and bohm] aren't really comparable, at least not if "orthodox QM" is taken to mean the ordinary shut-up-and-calculate version (which is basically what the purely positivist version of the Copehagen interpretation is, although some people use 'Copehagen interpretation' to mean the view that the collapse of the wavefunction is a real physical event), which is just a recipe for making predictions about probabilities without any assumptions (one way or another) about hidden variables, other worlds, or any other aspect of reality that can't be tested directly. Of course, you could also use the formalism of Bohmian mechanics as a recipe for making predictions, without any assumptions about the "reality" of hidden variables or the pilot wave, but this isn't what people usually mean by Bohmian mechanics.

Yes, I completely agree. If you take "orthodoxy" to just mean the "shut up and calculate" attitude, then it's true that "orthodoxy" and Bohm are no longer on an equal footing: one is a mere calculational algorithm, while the other is an actual *theory* about physical processes in the world. (But of course, people who support "orthodoxy" in fact *don't* take this attitude seriously, or at least consistently. They invariably accept the very non-positivist claims that the wave function alone provides already a complete description of physical states, contra "hidden variables.")

I also agree that, if one takes a hard-core positivist attitude toward Bohm's theory, one is simply left with a calculational algorithm -- the same one, in fact, that we called "orthodoxy" just above. In other words, if you insist that any theory *just is* its calculational algorithms, you would have a difficult time understanding what all the fuss (in regard to Bohm vs Copenhagen vs this vs that) is about.

Of course, that attitude is just dumb. I mean, seriously, what scientist actually thinks it's *wrong* to try to figure out how things work? What the heck are the string theorists doing then? Or all the astrophysicists trying to figure out exactly what happens during a core collapse supernova? Or basically every other physicist and scientist currently in existence? Sure, it's always useful to figure out what happens first -- to be in a kind of purely descriptive mode -- but then the whole point is to try to dig deeper and ask "what's going on that makes it come out this way?" or "why does it come out this way instead of some other way?" etc. Practically every important discovery in the whole history of science is an example of this. Gases obey PV = const... but *why*, what is going on physically that makes the pressure vary this way? (Then, 200 years later or whatever, "Oh, the kinetic/atomic theory explains this...") Or: Kepler noticed that planets move in ellipses, etc., but *why*? Newton provided a big part of the answer to those questions with his theory of gravitation. Or: some materials exhibit superconducting or superfluid behavior at certain temperatures... but why? So then people come up with a theory which explains that in terms of some deeper facts about the nature of the substances. Asking why (or "how", which amounts to the same thing but some people for some reason make a big deal over this distinction) is *essential* to good science. Indeed, it is practically synonymous with good science.

In other words, to take this positivist attitude seriously is to spit in the face of the whole entire history of science. So it's no wonder the people who advocated this in the 1920's cooked up a big philosophical set of pseudo-arguments for why the case of quantum theory was fundamentally different, why we really had to accept this new attitude not just because of philosophy but because of certain problems inherent to microphysics, etc. etc. But de Broglie and Bohm put the lie to it by showing explicitly that it's all bogus, that it's not impossible to give a coherent physical theory which tells a comprehensible physical story to explain physically why the measurements come out the way the calculation algorithm says they should. In short, they proved by explicit example that the *real* basis for the Copenhagen hegemony was *not* physics discoveries, but, rather, philosophical bias. Hence the irony of contemporary Copenhagen supporters dismissing Bohm on the grounds that his theory is just philosophical bias. In the end, it does come down to philosophical questions (such as: is there an external physical world, and is it the task of physics/physicists to figure out what it's like and how it works), but the right question is not "who is less biased?" but rather "which philosophy is reasonable?" That's why I'm happy and proud to admit that it's because I'm a realist and a scientist that I am "philosophically biased" in favor of Bohm, GRW, etc. as against "shut up and calculate".

 

[NateTG]

If there are experiments for which 'plug and grind' QM is ambiguous, and Bohmian Mechanics makes falsifiable predictions, then the two are clearly distinct from a scientific perspective, and, Bohmian Mechanics can, at least in theory, be tested there. Barring any such scenario, choosing one over the other is a matter of taste.

Bohmian Mechanics is primarily interesting from a philosophical perspective because it AFAICT provides a deterministic realist interpretation of QM, and thus, Bell's Theorem notwithstanding, if we assume a 'big bang', Bohmian Mechanics is a local realist interpretation of QM. (Locality follows readily from common history and determinism.)

 

[ttn]

If there are experiments for which 'plug and grind' QM is ambiguous, and Bohmian Mechanics makes falsifiable predictions, then the two are clearly distinct from a scientific perspective, and, Bohmian Mechanics can, at least in theory, be tested there.

The classic example of this is "tunneling times". Imagine a particle initially in a metastable bound state, out of which it will (asymptotically) tunnel, i.e., emerge with positive energy at some large radius. What does OQM say about (say) the average time you have to wait before the particle appears at some particular radius? It's not clear how to calculate such a thing in OQM -- and indeed not clear that there is any way to do it. Bohm's theory on the other hand can answer such questions unambiguously. Or so it seems. I don't have any interest in discussing this, really, but I just wanted to note the existence of a huge literature on this specific point.

Barring any such scenario, choosing one over the other is a matter of taste.

Sure, "taste". For example, whether one prefers a mathematically precise formulation which is 100% crystal clear about what it says exists and happens, or prefers instead something "unprofessionally vague and ambiguous" (like such-and-such happens whenever there's no "measurement" happening, while so-and-so happens instead when a "measurement" is happening, and with no further clarification or definition about what the heck a "measurement" is). So, yeah, it's merely a matter of taste: as in, whether one prefers the taste of a good theory to a bad theory.

Bohmian Mechanics is primarily interesting from a philosophical perspective because it AFAICT provides a deterministic realist interpretation of QM, and thus, Bell's Theorem notwithstanding, if we assume a 'big bang', Bohmian Mechanics is a local realist interpretation of QM. (Locality follows readily from common history and determinism.)

Bohm's theory is not local. But then, neither is any other theory which agrees with the experimental results violating Bell's inequality. That's what Bell's theorem proves. Nonlocality is a fact of the world which all empirically viable theories are going to have to include (and, so, they do). People who dismiss Bohm's theory on the grounds that it is nonlocal aren't paying attention.

 

[ueit]

Bohm's theory is not local. But then, neither is any other theory which agrees with the experimental results violating Bell's inequality. That's what Bell's theorem proves. Nonlocality is a fact of the world which all empirically viable theories are going to have to include (and, so, they do). People who dismiss Bohm's theory on the grounds that it is nonlocal aren't paying attention.

It is not true that "nonlocality is a fact of the world". A fully deterministic theoy cannot be ruled out by Bell because it denies the possibility of statistical independence between the source and detectors. All classical theories are of this type and they are not therefore eliminated by Bell.

 

[metacristi]

I've promised once that I'll never return on this forum as much as Zapper Z remains moderator here [nothing personal but I don't think that a too strong authoritarianism is a good thing for science, I still maintain that] but seeing, for some time now, the quality exchange of ideas here I cannot resist writing again (at least today :-)).

The main argument of those defending the 'shut up and calculate' stance is indeed not too far from that of logical positivists. According to this point of view - given that the 'interpretations' do not really make novel, potentially testable, predictions (only the standard mathematical formalism does, around which almost all interpretations are constructed) - we cannot accept them (the 'interpretations') as scientific (in short the interpretation part does not really account for the empirical success of the theory and there is under-determination at this level now, possible forever). Not surprisingly then that such positivists label all interpretations as being 'philosophy' not science.

I would not consider the positivistic stance without any merit (in the case of QM) but I think we can safely attack the claim (of some) that this is the only rational stance for the moment. Fact is that all valid compounds 'formalism-interpretation' are capable to account for the observed facts (post hoc is enough) and they are empirically evolving at the moment (for example Bohmian mechanics has been able to account basically for all new experiments so far though sometimes some auxiliary hypothesis are needed; the same is valid for the other valid interpretations).

In this respect the theoretical constructs used by these compounds 'mathematical formalism-interpretation' (even Copenhagen Interpretation does have such constructs) can be seen as necessary to account for the empirical success of the ‘compound’ they are part of; thus we can see, at limit, every such compound 'formalism-interpretation' as forming at least as a valid scientific program deserving to be pursued further.

Of course if we take in account now the other traditional (but weak) requirements of actual scientific methodology (ontological and logical simplicity, capacity to unify things thought previously as being not connected, coherence with other accepted parts of science etc) we can even make a weak distinction between the different existing compounds 'formalism-interpretation'.

Here clearly (though no interpretation is without problems) Bohm's interpretation appears [with its auxiliary assumptions - like Vigier's explanation of why electrons do not fall into nucleus - or the actual absence of a Lorentz invariant relativistic version] on a lower level than the evolutions of Copenhagen Interpretation (the same is valid for MWI or the transactional interpretation, for other reasons of course etc) but we cannot say that these alternatives are ‘dead ends’ (as some argue wrongly; L. Motl among the most vociferous (at least in the case of BM and TI, I wonder why he is not against MWI which after all 'want to modify physics' too with its resort to possible, but untestable, worlds).

The above mentioned ‘weak’ distinction is informative but not prescriptive, it is still fully rational at the moment to pursue such alternative programs in spite of the fact that currently they comply less with the accepted scientific methodologies (the decision to pursue a certain program as the first choice, personal, program does not automatically involve ontological commitments or claims of epistemological privilege). Indeed the history of science teach us that even seemingly degenerative programs at a certain moment can become theoretically and empirically progressive later (when the ‘background’ is prepared for their emergence) so it would be a big mistake to bar still legitimate directions of research (crucial breakthroughs could be lost forever).

--------------------------------------------------------------------------------------------
"...even the most obvious connections remain unseen if we are constantly brainwashed that such connections are impossible or meaningless" - K. Popper (paraphrased)

 

[RandallB]

A fully deterministic theoy cannot be ruled out by Bell because it denies the possibility of statistical independence between the source and detectors.

Could you clarify exactly what the “it” is in “it denies” in your point here.
(“A fully deterministic theory” or “Bell”)

I often have trouble following the logic of “local” proponents that do not accept the idea of a theory building a version of local in a non-local way (non-local Bell way). Which is why IMO BM is as viable as QM, and they are both non-local.

Taking an “Occum’s” view of which is better between BM & QM; they may be one, but I can not tell. Any more than trying to define if Leibniz Calculus is better than Newton’s or if it’s just a matter historical preference that the Leibniz method has become preferred by the majority but still not all, just like QM is used and preferred over BM by most. They give the same non-local results, and maybe both have a place. Example interference problems seem to be more easily understood using BM; while application work in particle physics seems to have made the best progress using QM.

 

[MaverickMenzies]

I think the real problem with all of these interpretations is that they are all after the fact. In other words, we discovered the mathematical formalism that could predict the various empirical effects that were observed and then we tried to make sense of the meaning of the formalism. I think that quantum mechanics will only make sense if one can discover a physical principle from which the formalism can be derived.

 

[DrChinese]

All classical theories are of this type and they are not therefore eliminated by Bell.

You can say this 100 times and it is still not true. Classical theories give results that are inconsistent with observation. I.e. they do not follow the cos^2 rule. The reason is: the observer must be taken into account in explaining the result, a mechanism for which classical theories - because they are by definition classical - are unable to do. Specifiying a common prior history answers nothing until you can tell us how it ties in.

 

[NateTG]

You can say this 100 times and it is still not true. Classical theories give results that are inconsistent with observation. I.e. they do not follow the cos^2 rule.

Falsification by experimental result is not the same thing as falsification by Bell's Theorem.

Specifiying a common prior history answers nothing until you can tell us how it ties in.

It's really quite simple, and simultanteously rather unsatisfying:

Let's assume, for a moment, that the universe is deterministic, not necessarily local and has a definite beginning. Since the universe is deterministic, we can write a (not necessarily finite) list of all of the uncertain events that occur in the universe, $\vec{h}$. Notably, this list is not dependant on time - so we can postulate that it's the local hidden state of the big bang, and has propagated forward locally from there.

Unless the HUP is somehow falsified (not likely) it's impossible to make any determination about mechanisms, so you could readily think of maxwell's demon runnning around and pulling strings if you like.

 

[ueit]

Could you clarify exactly what the “it” is in “it denies” in your point here.
(“A fully deterministic theory” or “Bell”)

I don't use "it" for persons, so the answer is "A fully deterministic theory”.

I often have trouble following the logic of “local” proponents that do not accept the idea of a theory building a version of local in a non-local way (non-local Bell way). Which is why IMO BM is as viable as QM, and they are both non-local.

AFAIK there is no relativistic BM, but we have QED.

1. The only theory we have that deals with the nature of space and time itself (general relativity) says our universe is local.

2. As I said many times on this forum, Bell's theory isn't a problem for local deterministic theories because these theories do not allow for statistical independence between the detectors and source. A local deterministic universe is like a clock. Bell's theorem requires that you turn independently two "wheels" (detector switches) but you just cannot do that without breaking the mechanism. Therefore the assumptions used for the derivation of Bell's theorem are logically incompatible with the assumption that we live in a local deterministic universe. Bell's theorem only proves that the law of non-contradiction is still valid, which is hardly a remarcable fact.

From 1. and 2. we can see that a local theory is to be preferred (Occam’s razor).

I agree however that a non-local explanation is much better than no explanation at all or a non-realistic one.