Local QM? MWI, RQM, QFT, LQM, + ?

[Schrodinger's Dog]

One can be shocked by its weirdness. In fact, if one isn't, then one hasn't understood it.



How to make you see that there are no new realities *invented*, but that they FOLLOW if you strictly apply the axioms of quantum theory to everything, the observer included ?

THIS is why I'm referring to "the light emitted to the back of Andromeda". To someone who intuitively thinks that the heavenly bodies are just holes in a kind of big celestial sphere, the concept of "light emitted to the back of Andromeda" doesn't make any sense. When you explain to him some stellar models, and electromagnetism and wave propagation in space, he might object that all this theorizing just helps you calculate some things about the light coming from Andromeda (which, in his mind's eye, is STILL just a hole in the celestial sphere). And he might object that you *invent* some light emitted to the "back of Andromeda" just to fit your picture.
The argument about *inventing* new realities sounds exactly similar. When you consider that the "observer" is describable by quantum theory, together with his system, and you apply the axioms of quantum theory to the overall system, then you have to assign a hilbert space of states to the "observer+system" system, and a hamiltonian.
When you do that, you find out that your observer+system ends up in a kind of quantum state which looks like:
|observer_saw_A> |system_in_state_A> + |observer_saw_B> |system_in_state_B>

I'm not inventing this, everyone recognizes this, it is even written down in von Neuman's book "mathematical foundations of quantum theory". He calls it "the pre-measurement interaction".

von Neumann (very well aware of the difficulty), then goes on saying that "nature now switches from one kind of process to another at some level" (from "process 2" to "process 1"), and the observer, which was in two states, suddenly finds himself into one state (collapse).
von Neuman even almost hints at MWI, when he says that he cannot place this switching of process 2 to process 1 anywhere, strictly speaking, but that it must happen in between the system level, and the observer's conscious experience.

So the very fact that strictly applying standard quantum theory to the "observer+system" system, leads to an observer in a superposition of two "states of observation", should indicate that one doesn't INVENT any "new realities". One has to EXPLICITLY CUT AWAY part of the answer quantum theory gives us. We have to CUT AWAY the different superposed "states of observation" by hand if we want to end up with a quantum state of the observer in which he has one unique observation. It is this cutting away which gives rise to all the problems.



I would like to know exactly what he understands by "me being wrong" in this context, and how he is going to show this. Because, again, I'm not claiming that MWI is ultimately true. I'm saying that MWI is the natural view which goes with unitary quantum theory, and that this view can save you a lot of trouble, avoiding paradoxes which didn't have to be.
So he bets his doctorate upon that he's going to show me that MWI is NOT the natural view on unitary quantum theory ? I really wonder how he's going to handle that. Tell me when he's given up, I'll mail him my postal address (for his doctorate)

considering he feels the current theory is wrong then yes, pretty much I'm sure he would, he's got issues with most accepted facts though, that's his opinion. He's currently at odds with using imaginary numbers and is trying to find a 3d-spin solution without resorting to imaginary numbers, but he's almost given up in spherical polar co-ordinates even with i.

He's the sort of person who's vigorously looking into the cracks to see if he can find anything. OK maybe not his PhD but he still thinks you are making airy fairy philosophical hand wavey gestures.

Again his words not mine

I know what your saying, and I'm not majorly in disagreement, but I think he's probably right, the assumption is based on flaws. Anyway, I think we've extended everyones knowledge of MWI, and maybe had a little fun while we're at it: I guess we'll just have to agree to disagree, although to be frank I now don't dismiss it as sci fi, and have learned a great deal about what lies beneath. So thanks a bundle for that Vanesch and I hope this has been educational to more people than just me

 

[vanesch]

However, the reason I mentioned the paper above to you was quite different. Linear equations in physics are usually regarded as approximations of nonlinear ones. From this point of view, it seems rather unreasonable to adopt an interpretation that makes sense only in the linear case.

I agree. However, the funny thing with QM is that the slightest non-linearity destroys the strict locality of it in an EPR setting. It is only when strict unitarity is respected that one can avoid signaling FTL with entangled systems. As I said, Penrose thinks somehow that gravity might be responsible for this breaking of unitarity (but it would then as well give problems with GR on a small scale), the reason for this being that the "time" used in the Schroedinger equation will depend upon the "gravitational quantum state" or something of the kind. However, this is thinking out loud, and I don't think he got this really up and running.

So it is not that easy to modify quantum theory into a "slightly nonlinear version" without running into a lot of troubles that are absent in the strictly linear version ; and even in that case, the MWI interpretation will then still be a good approximation for the "linear part" (even if it is only limited to a few milliseconds, and a few thousand kilometer, say, a domain over which GR shouldn't be fully valid in that case, given the non-local character of the non-linearity it introduces). But such deviations from strict linearity should, sooner or later, be empirically observable and contradict interference predictions by unitary quantum theory. The EPR-Bell situation will then probably not arise outside of this "domain of validity of the unitary approximation", and its very resolution will tell us then what exactly happens.

Remember that I'm only a proponent of MWI in as far as unitary quantum theory is valid, because I think that, *within this domain of validity*, it gives one the most natural description as derived from the formalism, and explains quite in a straightforward way, things which seem almost incomprehensible in a "projection-based" view, mainly EPR situations and quantum erasure experiments. As of now, we haven't any idea of whether this strict unitarity is universally valid or only restricted to a certain domain. We only know that there are difficulties including gravity - but we don't know how serious these difficulties are. So in absence of any empirical indication, nor good formal reason, to give up unitarity, and knowing that it will introduce more problems than it solves, for the moment I keep it.

 

[Demystifier]

Fair enough, vanesch!

 

[Anonym]

I don't know if you noticed it, but we have, as of today, only an incomplete description of physics. So we don't HAVE the postulates of all of physics.

Vanesch, come on! I don't know if you noticed it, but the formulation of the complete set of the principal postulates of Geometry was achieved about 3000 years ago. I don't know if you noticed it, but it did not stop the development of the Geometry which is continued successfully also today. They are the Rules of the Game and not the Game itself. Indeed, you may define them according to any of your interpretations. I have nothing against that.

 

[Hurkyl]

Vanesch, come on! I don't know if you noticed it, but the formulation of the complete set of the principal postulates of Geometry was achieved about 3000 years ago. I don't know if you noticed it, but it did not stop the development of the Geometry which is continued successfully also today. They are the Rules of the Game and not the Game itself. Indeed, you may define them according to any of your interpretations. I have nothing against that.

Not even close. Euclid's postulates are for one specific entity (a Euclidean plane), and they were far from complete.

 

[Schrodinger's Dog]

The superposition principle is not falsifiable ?
/snip

I think that if he had one, he would have given it... but try along !
I'm pretty sure it will come down to just a statement of "nah, that's simply too crazy an idea" or a similar derogatory expression of emotion. I know of no *rational* argumentation against MWI (which is also not an argument against quantum theory in general). In fact, MWI *saves* quantum theory from two deadly arguments against it, which is 1) non-locality and 2) inconsistency concerning the "measurement apparatus considered as a system".

Can I just say I'm being a devils advocate here now, after listening to your ideas, I think it has merit, and that this is valid criticism if you see what I mean. And I hope I haven't offended anyone by being forthright, if I have give me a few days off and I'll happily agree I deserve it, I really do think Vanesch that amongst the mentors you and ZZ,Berkman,Evo, etc(in no order of prefference, and don't forget if I forgot your name I'm picking favourites, I just am crap with names, Space Tiger ) et al and many of the others are quite excellent in conveying your ideas, and that's why I have such a respect for this forum. And your cohorts of supporters are supporters because of that, and I respect them also.

I will uphold one caveat though, my colleague thinks you're wrong, he knows an infinite amount more than me(ok not infinite) But you see what I mean.

Now that said, I think their are flaws, and I think my colleague has a point, but I also after listening to your very clear ideas, and OK throwing in a few spanners think you have a very good case for a theory, if only that it's a hypothesis atm. OK I don't think it's a correct one, but I do think it's a viable idea. But correct and viable are meaningless when you're talking about ideas and hypothesis, and speculation. Ok it's better than ST, and ok I agree I have been a bit rash, and a bit of a

Again thanks for the dialogue, it's been emotional as Vinny Jones once said, but of course in a positive way.

It's Ok I'm not going to use a resort to authority to justify my position, he's very keen on trying to find the flaws, his motivation is no different from yours, you just have a different way of going about it

Oh and by wrong he means you have nothing but a theory that is flawed to back up your argument, therefore he thinks since there is no evidence or proof you may be involved in pure philosophy, I'm off work 'til Monday but I'll ask him to read this. He's an amiable fellow, if he thinks he's wrong he's the first to admit it.

 

[wm]

considering he feels the current theory is wrong then yes, pretty much I'm sure he would, he's got issues with most accepted facts though, that's his opinion. He's currently at odds with using imaginary numbers and is trying to find a 3d-spin solution without resorting to imaginary numbers, but he's almost given up in spherical polar co-ordinates even with i.

Re forsaking imaginary numbers: see work on Geometric Calculus by Hestenes et al.

For example: http://modelingnts.la.asu.edu/ wm

 

[Schrodinger's Dog]

Re forsaking imaginary numbers: see work on Geometric Calculus by Hestenes et al.

For example: http://modelingnts.la.asu.edu/ wm

Thanks for that I'll have a look

Your first link doesn't work BTW. Or is it not meant to? Ah I see it's a suggestion my mistake.

Anything quickly accessable?

http://www.mrao.cam.ac.uk/~clifford/introduction/intro/intro.html

http://en.wikipedia.org/wiki/Geometric_algebra

http://citeseer.ist.psu.edu/context/105756/0

Ok got something thanks.

Lucky I recently researched Imaginary numbers really.

 

[CarlB]

There is a somewhat simpler way of geometrizing QM (and eliminating imaginary numbers) than Hestenes', see the article on geometric representations of the density matrix by Havel, Doran and Furuta:
http://www.mrao.cam.ac.uk/~clifford/publications/abstracts/hd_density.html

The above gives two methods. The first, the obvious one, is used in my book. I need to add a reference to the above, as I was unaware of it when I started writing. See chapters 1 and 2 for an easy introduction to the ideas:
http://brannenworks.com/dmaa.pdf
(The above is "easy" in that it builds on what you already know about Pauli and Dirac spinors and all that. Other authors tend to jump off into Clifford algebra land and so end up writing for specialists only.)

The second method discussed in the Havel, Doran & Furuta paper is similar to Hestenes' technique, which is used for spinors, rather than density matrices. And there is also another way of geometrizing the Dirac equation that is discussed very briefly (and in a difficult to understand manner, I think) here:
http://en.wikipedia.org/wiki/Dirac_equation_in_the_algebra_of_physical_space

I think that the above is particularly inelegant. I know it's listed in the literature, but even Hestenes' method is easier and more natural. For methods that involve just spinors (not the density operators Havel, Doran and Furuta used and I use), the incomparable Baylis has an excellent review and comparison article that will explain the reasoning behind the various choices:
http://www.arxiv.org/abs/quant-ph/0202060

I'm trying to get myself motivated to start a wikipedia article on these various methods of geometrizing quantum mechanics. One of the problems with doing this is that the truth is that one has to know a substantial amount of Clifford algebra before any of this makes sense. Another problem is that it seems that ALL the various authors use completely incompatible notation. And a third problem is that there are many many ways of deriving the same thing, (as is the case for any true thing), and everyone seems to prefer different ways of doing the derivations. And finally, while the field has been in play since Hestenes' articles of the early 1980s, so far there is no generally accepted result that has extended anything beyond where QM already has gone.

Carl

 

[Schrodinger's Dog]

Thanks I'll show my colleague, he'll probably be interested.

 

[Anonym]

Not even close. Euclid's postulates are for one specific entity (a Euclidean plane), and they were far from complete.

Dear Mentor,

I studied P.K. Rashevski “Riemann Geometry and tensor analysis” before I finished high school. At the same time I read original papers by N.I. Lobachevski and the Russian translation of J. Boljai. Before writing the post concerned the axiomatic of physical theory, …

Let me explain to you the conceptual content of my disagreement with Vanesch. Vanesch stated that the superposition principle is universally valid physical postulate. However, it is too restrictive and not a physical postulate at all. It is only the inherent feature of the mathematical framework called linear Hilbert space with very restrictive class of operators (transformations):linear operators. The mathematical framework is only the empty arena suitable or not suitable for the specific applications in physics.

In addition, Vanesch discussions of MWI remind me the N.Bohr style of presentation, for example, in the paper “The Quantum Postulate and the recent development of Atomic Theory”, Nature, 121, 580 (1928):
“… the formulation of the quantum theory, it seems, as we shall see, that its essence may be expressed in the so-called quantum postulate, which attributes to any atomic process an essential discontinuity, or rather individuality, completely foreign to the classical theories and symbolized by Plank’s quantum of action.”

As far as non-relativistic CM vs non-relativistic QM is considered, just the opposite is correct. In view of our today empirical knowledge, this definition express only the perfect confusion of the writer.

Forum Rules:”“Posting the same topic across multiple forums or multiple threads is considered spam and is not allowed.”

Vanesch insist to make propaganda of MWI in each session of discussion, does not a matter what it is specifically:’the wave packet description”, “ non-locality” or present one, etc. It is not written in any standard textbook on QM or QFT that MWI is universally valid interpretation of QT. Vanesch propaganda is in contradiction with the Rules of PF.

The self-obvious postulate of the PF is: Don’t confuse kids.

I wish that the future generation of physicists will understand Quantum Physics. Are you also?

Dany.

 

[Schrodinger's Dog]

To be fair though Anonym, I started it and was delighted to play discordant antagonist to Vanesche's concerto

 

[Demystifier]

It is not written in any standard textbook on QM or QFT that MWI is universally valid interpretation of QT. Vanesch propaganda is in contradiction with the Rules of PF.

The self-obvious postulate of the PF is: Don’t confuse kids.

But what if some kid asks interpretational questions on QM to which answers are not written in any standard textbook? Should we tell him/her: "Shut up and calculate!"? Or that it is impossible to answer such questions? Or that some possible answers exist but that there is no yet consensus among experts? In the latter case, shouldn't we explain them these possible answers?

 

[vanesch]

Let me explain to you the conceptual content of my disagreement with Vanesch. Vanesch stated that the superposition principle is universally valid physical postulate.

No, I didn't state that. I state that *quantum theory* takes as a postulate, the superposition principle. It is its basic principle ! In the same way as GR takes as basic postulate, that there is a pseudo-riemanian spacetime manifold. It is the starting point of the theory.
Starting from this postulate of superposition, the natural mathematical representation is a (projective) hilbert space. In fact, stating that the space of physical states is a (projective) hilbert space, or stating that the superposition principle is supposed to be valid, is the same statement.

However, it is too restrictive and not a physical postulate at all. It is only the inherent feature of the mathematical framework called linear Hilbert space with very restrictive class of operators (transformations):linear operators. The mathematical framework is only the empty arena suitable or not suitable for the specific applications in physics.

... and in quantum theory, it is, BY POSTULATE, the arena in which nature is supposed to act.

In addition, Vanesch discussions of MWI remind me the N.Bohr style of presentation, for example, in the paper “The Quantum Postulate and the recent development of Atomic Theory”, Nature, 121, 580 (1928):
“… the formulation of the quantum theory, it seems, as we shall see, that its essence may be expressed in the so-called quantum postulate, which attributes to any atomic process an essential discontinuity, or rather individuality, completely foreign to the classical theories and symbolized by Plank’s quantum of action.”

As far as non-relativistic CM vs non-relativistic QM is considered, just the opposite is correct. In view of our today empirical knowledge, this definition express only the perfect confusion of the writer.

Well, if my style of discussion is of the level of a N. Bohr article in Nature, I feel in good company

Forum Rules:”“Posting the same topic across multiple forums or multiple threads is considered spam and is not allowed.”

Vanesch insist to make propaganda of MWI in each session of discussion, does not a matter what it is specifically:’the wave packet description”, “ non-locality” or present one, etc. It is not written in any standard textbook on QM or QFT that MWI is universally valid interpretation of QT. Vanesch propaganda is in contradiction with the Rules of PF.

I don't think so. The problem is that in many threads, the interpretational issues come to the foreground, and in many cases, the MWI interpretation sheds some interesting light on the issue. The most interesting light I think is in the case of "non-locality" in the EPR situation, which comes up in many discussions. I think it is allowed to point this out, no? However, MWI is often met with 1) ignorance of what exactly it states, and 2) a strong emotional rejection from the part of some posters. I try to explain to these posters that MWI is NOT the totally crazy idea of a few lunatics, but is taken quite seriously by several people, and I try to point out its advantages in resolving certain issues. As I said, the ONLY objections I know against MWI, are of the emotional kind.

That said, you should acknowledge that I'm not forcing MWI through anybody's throat, I'm just informing people, and try to get them beyond the "emotional rejection" part, which usually doesn't allow them to even understand exactly what MWI is saying. Now, it is true that in doing so, I sometimes point out the evident logical contradictions in the "standard" Copenhagen view, which are nevertheless swallowed without any reflection.

You might also have noticed, if you read my contributions carefully, that I never claim MWI to be "true", but just a conceptual tool to UNDERSTAND quantum theory ; and especially, to understand how certain bizarre predictions of quantum theory come about.

The self-obvious postulate of the PF is: Don’t confuse kids.

I wish that the future generation of physicists will understand Quantum Physics. Are you also?

Yes, and I'm profoundly convinced that taking on an MWI view (amongst others!) helps doing this.

 

[Anonym]

To be fair though Anonym, I started it and was delighted to play discordant antagonist to Vanesche's concerto

Indeed, I tried to play second violin but it doesn’t sounds to me that bad. Always an improvement possible. After all, the well time-treated (observer-dependent) counterpoint is the art of fugue all about. I enjoy Vanesch discussions very much. I intend to write a paper with a purpose to demonstrate that more than 40 years ago it was already shown that the M.Born statistical interpretation have no room in quantum mechanical formalism. It is direct consequence of my discussions with Vanesch. According to the standard rules, he should be co-author of that paper. However, I fear even to ask his agreement.

Eventually, the principal postulates are only Global Guidelines in the actual research. Obviously, they altogether are so restrictive that the only adequate formulation of the corresponding Chapter will satisfy all of them simultaneously. Our discussions are around the measurement theory. In his famous discussions with N. Bohr, A. Einstein did not talk about them, but referred to them in his statement “… ob der liebe Gott wurfelt” (Classical Physics). In contrast, N. Bohr invent freely the “new” postulates, but clamed that A. Einstein should not tell to God what to do. His logic seems to me ridiculous. All that similar to Jewish story with Chodesh Chodashim. Obviously, no physicist is allowed to enter that room by definition. However, if you are curious enough, you may travel to Idfu temple in Egypt and you will get an idea adequate for all practical purposes.

P.S. I like old music. How I find a good piece? Let say 500 years old. I look if an author is Anonym.

 

[Schrodinger's Dog]

Indeed, I tried to play second violin but it doesn’t sounds to me that bad. Always an improvement possible. After all, the well time-treated (observer-dependent) counterpoint is the art of fugue all about. I enjoy Vanesch discussions very much. I intend to write a paper with a purpose to demonstrate that more than 40 years ago it was already shown that the M.Born statistical interpretation have no room in quantum mechanical formalism. It is direct consequence of my discussions with Vanesch. According to the standard rules, he should be co-author of that paper. However, I fear even to ask his agreement.

Eventually, the principal postulates are only Global Guidelines in the actual research. Obviously, they altogether are so restrictive that the only adequate formulation of the corresponding Chapter will satisfy all of them simultaneously. Our discussions are around the measurement theory. In his famous discussions with N. Bohr, A. Einstein did not talk about them, but referred to them in his statement “… ob der liebe Gott wurfelt” (Classical Physics). In contrast, N. Bohr invent freely the “new” postulates, but clamed that A. Einstein should not tell to God what to do. His logic seems to me ridiculous. All that similar to Jewish story with Chodesh Chodashim. Obviously, no physicist is allowed to enter that room by definition. However, if you are curious enough, you may travel to Idfu temple in Egypt and you will get an idea adequate for all practical purposes.

P.S. I like old music. How I find a good piece? Let say 500 years old. I look if an author is Anonym.

You should include this discussion in your paper, if you ask me it's a very clear way of showing what MWI attempts to show, cut the chaff out, ie my posts though

 

[wm]

Vanesch:” QFT is not an interpretation of quantum theory, it is the application of quantum theory to a specific classical model (classical fields). As such, all interpretational issues remain with QFT in the same way as they remain with other applications of quantum theory.”

Allday:” One "law" that you can keep in mind is that quantum objects travel as waves and interact as particles”.

It is follow deterministically from your discussion with me in the Particle-Wave duality and Hamilton-Jacobi equation session that

There is no legitimation for M.Born statistical interpretation any more and it may be removed from the formalism of the Quantum Theory. Quantum Theory is the local field theory of the massive waves. No interpretation required.

I would welcome some elaboration of this last paragraph:

1. On what grounds is the Born statistical interpretation no longer legitimate?

2. How is ''collapse'' handled in QFT?

3. ''No interpretation required'' seems (to me) to be the Holy Grail of every theorist. Please elaborate; eg, on the ontology (''elements of reality'') associated with your view.

Thanks, wm