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Many interacting worlds approach is an original, equally flawed cousin of Bohmian mechanics

All the major "realist" attempts to reform the foundations of quantum mechanics – de Broglie-Bohmian mechanics, Ghirardi-Rimini-Weber-like collapse theories, and Everett-style many worlds – are known to suffer from serious diseases. To a large extent, "realism" itself is the problem.

Off-topic, physics: In Physics World, Sylvester Jim Gates Jr explains why he is Sticking With SUSY. Doing something else would be as unwise as to conclude that giant sequoia trees don't exist after looking at the U.S. East Coast only. Supersymmetry, a Bose-Fermi symmetry, is really needed to "deeply" explain the established fact that the quantizations of fermions and bosons are so analogous; and to cancel lots of destabilizing divergences.
I am still willing to admit that there is no truly "rock-solid proof" of the statement that "there cannot be any realist reinterpretation or 'improvement' of quantum mechanics". This sentence is composed of words and we don't really know what the "most general type of a theory we would naturally consider realist" looks like. We can't define it. Maybe a way to reformulate quantum mechanics "smells" realist and all the "novelties" of quantum mechanics are traded for another feature of the reformulation that seemingly does something else than to refute realism. I find the existence of such a "realist" reinterpretation – even in this vague, generalized sense – extremely unlikely but I can't really "prove" that it doesn't exist.

So I am always open-minded when I read about a "completely new" approach to the reform of the foundations of quantum mechanics. Every such an approach may only be abandoned after we actually identify its lethal flaw if it exists. Of course, the lethal flaws are well-known for the most notorious "alternative approaches" and most articles about such matters share these flaws. However, when something is sufficiently new, one has to look at it with a "new dose of potential enthusiasm". That was also the case of the "new interpretation of quantum mechanics" (note that before this sentence, I've managed to avoid the word "interpretation") that was hyped in Nature yesterday:
A quantum world arising from many ordinary ones (Nature, popular)

Quantum Phenomena Modeled by Interactions between Many Classical Worlds (by Hall, Deckert, Wiseman, Physical Review X, PDF)
I must have heard of "Physical Review X" ("X" probably stands for "XXX", or porn for short) but the shortage of meaningful papers in that outlet has made me forget about the existence of the journal again.

The very title shows that these men are at least trying "something new". The conventional "many worlds" inspired by Hugh Everett are meant to be "no longer interacting, completely decoupled" branches of a new type of the multiverse. The very reason why there are many such worlds in that (hopelessly sick) picture is that every observation, whatever it exactly means, produces some extra "splitting of the world[s]", and this splitting has to be irreversible because the observation itself is meant to be irreversible.

If they want to make these worlds interacting, they enter a completely new territory – an even more dangerous one, but also one with some potential hopes to discover something new that could make sense.

To make the story short, your idea that their new picture – the "many interacting worlds" (MIW) – is a variation of the "many worlds interpretation" (MWI) is an illusion of a sort. In fact, their picture may be viewed as a discretization of a completely different "realist" picture, the de Broglie-Bohm pilot wave theory (dBB).

The previous sentence along with this paragraph and the following one actually explains everything they have and you can't easily derive yourself within minutes. While dBB has "one classical position of a particle" along with "one classical wave" coinciding with the wave function and acting on the classical particle as a "guiding/pilot wave" (note that dBB has to postulate that there is no influence in the opposite direction: the particle can't affect the wave), the new MIW picture assumes that there are "many classical positions of a particle" – this degree of freedom is copied many times, to get a "statistical ensemble".

And at the fundamental level, the pilot wave is completely eliminated. It is assumed that one may reconstruct it from the statistical distribution of many particles. Such a replacement of \(\psi(x,y,z,t)\) by (infinitely) many classical positions \(\vec x_i\) may be viewed as a "discretization" of the probabilistic distribution. If you do that, you must also discretize the "guiding equation" for the particle's positions. This gives you some interactions between the individual "worlds", between the different positions \(\vec x_i\). While this procedure was motivated as an approximation to the pilot wave theory, they finally revert the rules of the game and declare the "approximation" to be more fundamental and correct than dBB itself.

Fine. So by now, you effectively know everything you need to know about MIW, the new proposal. It is not clear to me why they didn't explain this simple relationship to dBB clearly in Nature – the author of the article probably has no idea what the proposal is all about so she just wrote some vague science-fiction that could be sold as a popular description of every other article trying to "reform" the foundations of quantum mechanics. That's why.
Off-topic, polemics: If you have nerves for an exchange in which a notorious anti-science "End of Science" šithead is framed as a peer of Tara Shears and David Tong, watch this 39-minute debate. David Tong's comments are fresh, relevant, and true, and that's true for Tara Shears as well, but I think that without clearly explaining to the ordinary people why the likes of John Horgan are just irrelevant piles of stinky šit that haven't and won't ever contribute anything to the mankind, the ordinary listeners are inevitably going to consider Tong's comments as "just another voice" and because the number of Horgan-like šitheads is thousands of times larger than the number of string theorists, they are bound to "win" in these debates. Regardless of the stellar performance by the sensible guys, similar debates legitimize the likes of Horgan and make them stronger. There should be many more public debates between real scientists themselves.
The question is whether the equations representing the discrete/sampling approximation of the pilot wave theory by many interacting copies \(\vec x_i\) may be written down; whether this new picture reproduces at least those aspects of quantum mechanics in which dBB was semi-successful; and whether the new picture, MIW, is actually better or worse when it comes to the pathological features of dBB and perhaps new pathological features.

MIW could a priori be better than dBB. However, when you think about it for a while, it is not better. It is probably much worse and no canonical approximation of dBB of this sort even exists.

Note that while dBB still has a classical pilot that evolves according to the same Schrödinger's equation as the wave function in quantum mechanics – it is mathematically the same object with a different (PC term for "fundamentally wrong") interpretation than what it has in quantum mechanics – the new MIW picture doesn't have anything that behaves as the wave function. One is supposed to "approximately reconstruct" the wave function from the distribution of many position vectors \(\vec x_i\).

You may quickly notice that while it's easy to estimate the probability distribution \(\rho(x,y,z,t)\) from many "dots" in the position space, \(\vec x_i(t)\), you don't quite get the wave function\[

\psi(x,y,z,t) = \sqrt{ \rho(x,y,z,t) }\cdot \exp(i\phi)

\] because the analysis of the "local density" of the dots in a given region tells you nothing about the phase \(\phi\). Can they calculate or estimate \(\phi\) at all? If the answer to this elementary question is No, then it is clearly a huge problem. Quantum mechanics can't work without the variable phase of the wave function.

The answer to the question is, given the actual paper we look at, mixed. Equations (3) \[

m^k \dot{\vec x}^k(t) = \left.\frac{\partial S_t(\vec q)}{\partial q^k}\right|_{\vec q = \vec x(t)}

\] and (4) \[

S_t(\vec q) = \hbar\cdot \phi

\] are the only ones that are supposed to say something about the phase. They relate the phase of the pilot wave \(\phi\) to the classical action \(S_t(\vec q)\) – they are really the same thing. And the time derivative of this quantity is supposed to be equal to the velocities of the particles in a given region.

In dBB, it's the first derivatives of \(\vec x_i\) that are already determined by the pilot wave. Here, in MIW, the particles have "inertia", and it's the second derivatives – just like in Newton's theory – that are calculated from the positions of other particles. So it could actually work: the velocities are independent degrees of freedom defining the initial conditions and they could remember the (gradients of) phases. But whether they know the right equations that would make it work seems debatable. Equation (11)\[

m^k \ddot x_n^k = f^k(\vec x_n(t)) +r_N^k(\vec x_n(t); \vec X(t))

\] is arguably the most fundamental equation of MIW governing the evolution (second time derivative) of \(\vec x_i\), the many positions. Equation (11) is nothing else than Newton's equations for \(\vec x_i\) with some new forces \(f\) and \(r\) on the right hand side but how they are actually calculated remains unclear beyond some general comments about "what we want these equations to do in the limit".

There is one more reason to think that they don't actually know what to do with the variable phase. If you look for the word "phase", you only find it 3 times in the paper. The first "phase" says that phases are discussed by well-known equations (3) and (4) – which however reduce it to another ill-defined symbol in MIW, namely \(S\). The second "phase" talks about the "phase space" and it is therefore unrelated. The third "phase", one at the end of the paper, says that they may reproduce something about QM but only for ground states with a constant phase. So it clearly does suggest that the self-evident problem with the missing phase hasn't really been solved.

Even if you ignore this problem, the new "theory", MIW, ends up being at least as sick as dBB. A key lethal problem of dBB is that the action of the guiding wave on the particles is "non-local" so the theory depends on an "in principle measurable" action at a distance which violates relativity. The same thing holds for the corresponding "interactions between many worlds" here: the interaction is explicitly nonlocal. It's related to other flaws, the impossibility to incorporate the spin or the quantum fields – which may be viewed as relativistic effects in the context of quantum mechanics.

They also don't have any sensible reason why one of the \(\vec x_i\) vectors is "picked" as the "actual one" that is observed at the end (despite the courage with which they want to describe tunneling and the double slit experiment in their picture). Problems that MIW faces seem to be equal to the union of the problems that MWI and dBB have with the same question, so MIW is even worse than MWI and dBB separately. They have no story about what happens with the other \(\vec x_i\) that are no longer needed. And they can't even describe "truly non-commuting" observables such as the components of the spin \(\vec J\). Like dBB, MIW is another picture that (incorrectly) assumes that some observables (positions) are "more real" than others (others that don't commute with the positions).

For these and other reasons, MIW is at least as flawed as any other proposed "alternative" to proper probabilistic non-realist quantum mechanics in the literature. But at least, I appreciate that they have managed to present some ideas that are at least slightly original and that involved a new trick how to approximate things in other pictures and how to change the labels what is fundamental and what is not.

Despite these virtues, the paper is another example of the fact that such efforts are a hopeless enterprise and a huge waste of time. I could have been 99.9999% certain that there won't be anything really promising in the paper after I read the first sentence in the abstract. In that sentence, they say that MIW is a "continuum limit of a mechanical theory". What's bad about this description of the paper is that by the word "mechanical", they really mean "classical mechanical". Quantum mechanics for point-like particles is "mechanical", too! It just isn't classical. The implicit assumption that "mechanics has to be classical" is always a terrible sign and I will probably never read a paper whose abstract sells this fundamentally fallacious assumption because writers who write such a wrong statement simply can't have a chance to see deeper than the founders of quantum mechanics.

With the hindsight, the framework they wanted to codify is silly. You know, physics has made quite some conceptual progress in the recent 300 years. The mathematical frameworks we have to use are more complex than the mathematics that was sufficiently 300 or 400 years ago. But these guys want to undo not only the string theory revolution – obviously – and the quantum field theory revolution, but also the quantum revolution (like most "reformers" of quantum mechanics) and (this is new for them) even the classical field theory revolution. They would like to return physics to the paradigm of classical Newtonian mechanical equations (ordinary differential equations) for point masses (they clearly find even "classical partial differential equations" to be too hard). It's a really ambitious plan for a counterrevolution in physics and the probability that something like that may be intrinsically true (and get reconciled with all the modern discoveries of field theory, quantum mechanics, relativity, and fancier discoveries in particle physics) is infinitesimal.

The world just isn't a classical Newtonian clockwork!

If you are able to view the progress from Newton's mechanics to classical field theory (including special relativity and then also general relativity) to quantum mechanics to quantum field theory to perturbative string theory to duality-laden non-perturbative string theory to XY in the future as a trend, it's pretty obvious that the future XY theory or theories that will penetrate deeper into the wisdom of our Universe will be even more abstract and mathematically advanced, conceptually "even more quantum" and "more stringy" – even further from classical mechanics – than the current pictures.

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reader Avraham rosenblum said...

I spent enough time with George Ryazanov's GUT that also claimed to be able to get QM from classical Physics. Even though the guy is a genius but the theory is wrong.
Te Fermi satellite in space that picked up a super nova right when it happened proved Lorentz invariance
I have no more patience for crack-pot theories after that.

reader Anonymous said...

Isn't there a fundamental flaw with approximating QM with point like particles because the average force on the wavefunction is not in general the force on the average position (in particular forces that vary significantly on the lengthscale of the wavefunction)? isn't that the problem with pilot-wave QM? what does MIW have to handle this?

reader Luboš Motl said...

Dear Anon, neither dBB nor MIW, its discretization of a sort, depends on the assumption that "the average force is the same thing as the force at the average momentum" to produce predictions that agree with QM. You would only need this (wrong) identity to hold if you wanted to replace quantum mechanics with classical mechanics with the position and nothing else.

But that's not what dBB and MIW are doing. They replace the apparatus by the classical position plus the whole wave function - either explicitly, or via a discretization. So the average force that acts on the particle depends on this whole distribution and, according to dBB or MIW, clearly isn't equally to the "classical force at the average position".

dBB and MIW suffer from lethal diseases but not as obvious ones as what you wrote.

reader Fer137 said...


reader Dilaton said...

I just scrolled through this so far, and the "off-opics" stuck out somehow ...

Maybe serious good physicists such as David Tong and others should just stop intetacting with anti-science trolls at all ...? I mean just refuse talking to them, taking part in interviews, "debates", TV shows, etc if such events are organized, managed, or produced not by appropriately serious and honest people and it is clear that the goal of the event is not to explain things to an interested enough audience but to bully them and their work?

To get people positively interested in nice physics, discussions among experts themself as Lumo said, or presentations in formats that dont give the anti-science trolls any opportunity to negatively and incompetently interfer of what is getting explained, would be much better.

Please stop feeding the trolls and let them reproduce with themself until they extinct themself by genetic defects due to incest ...

Taking part in public TV debates etc does nothing but serve the self-promotion and popularisation of the agressive trolls ... :-/

reader Avraham rosenblum said...

What do you think of this idea in this video?
It seems to be a two universe idea that wants to explain inflation

reader Eclectikus said...

On the other hand for any discerning viewer is easy to discriminate between the nonsenses and simplicities coming from the journalist, and the compelling arguments, historical examples and vision of real and active physicists (a theoretical and an experimentalist moreover, covering the two aspects of debate). And in that sense this kind of talk is rewarding and enlightening, except perhaps for the most clueless people, which in any case will be as immune to arguments like John Horgan himself.

reader timeforsmolintoresign said...

Dear Lubos,

After several decades of promoting one failed "theory" after another, is it not time for Lee Smolin to step down. Einsten said the most important attribute for a scientist is character. One second Lee Smolin is hyping Garret "Ed Witten is a Dick" Lisi as fabulous and the next Einstein, while writing pseudoscience papers with Lisi, and the next moment he is stating he never really believed the hype himself, which he instigated in an unprecedented nuclear media firestorm.

Now he is hyping several other failed theories, while claiming to work on M Theory himself. Lee Smolin writes at the blog of another failed physisict: , "Fifteen or twenty years ago it was possible to say that string theory was more promising than its alternatives, and indeed 15 years ago I switched my research from LQG to M theory. But I think that any objective evaluation of the evidence has to credit much more substantial progress has taken place since concerning the alternatives; especially spin foam models, but also other background independent approaches including shape dynamics, CDT, group field theory and tensor models, etc.

To support this I would point to the fact that much more is known from spin foam models about the challenges it faced 15 years ago, including substantial recent results on the emergence of GR in the semiclassical limit, the entropy and temperature of generic black holes, the elimination of cosmological and black hole singularities, finiteness, etc.

So, I would urge my string theory friends who think they know the answer to the question to have another look. There is a whole generation of brilliant young theorists working on alternatives to string theory you should meet!


Is Lee Smolin liltte more than a characterless perpetual hyper of random words strung together? "15 years ago, including substantial recent results on the emergence of GR in the semiclassical limit, the entropy and temperature of generic black holes, the elimination of cosmological and black hole singularities, finiteness, etc."

Is he not damaging physics with his never-ending false hype and deceit?

reader W.A. Zajc said...

Against my better judgment, I decided to have a quick look at this MIW paper. It’s not for the squeamish. I had the same visceral reaction as when seeing a person covered with sores, scabs and pustules. For that’s what the MIW paper is - the Schrodinger equation (in effect) encrusted with discretizations and an oozing auxiliary framework involving other worlds and potentials between them. If this is what underlies quantum mechanics I will find another line of work.

I am always struck by the fact that these ‘alternative’ formulations of QM are likely to break the first time they encounter even the simplest two-body wave function Psi(x1,x2) for two bosons or fermions. Not to mention the passage to relativistic systems, the Dirac equation, pair creation, loop effects, many-body systems, the calculation of g-2 for the electron, etc., etc. When you have to work really hard to get a poor simulacrum of the 2-slit experiment, it should be a pretty big hint that you’ve gone off in a profoundly wrong direction.

reader Leo Vuyk said...

Lubos, You wrote:"the new MIW picture assumes that there are "many classical positions of a particle" – this degree of freedom is copied many times, to get a "statistical ensemble".
And at the fundamental level, the pilot wave is completely eliminated. It is assumed that one may reconstruct it from the statistical distribution of many particles."
May I assume that that statistical ensemble could be spread over many copy universal bubbles grouped as an ensemble around the big bang in its centre? called Raspberry Multiverse?

reader Justin said...

Lubos is correct that Bohmian mechanics is flawed. Unfortunately he seems to have a poor understanding of the construction of Bohmian mechanics, and it's implications. In 1932 Von Neumann had published a result which was believed by many to rule out the existence of hidden variables. David Bohm was teetering on the edge of accepting quantum mechanics, and he went to visit Einstein around this time. After Bohm left, he was completely changed by Einstein's wisdom. He was convinced quantum mechanics wasn't the final description of nature. It was because of this meeting that Bohm began to look for a way to construct a realist theory of quantum mechanics in contradiction to the widespread belief that Von Neumann had shown that no such theory could exist. So, he tried to find the most naive way of constructing such a theory: make the hidden variable the position itself. By doing this Bohm completely reproduced the predictions of quantum mechanics albeit in a realistic picture of nature.

What Lubos fails to mention is that Bohm had only constructed his theory as a counterexample to Von Neumann. Bohm himself rejected his very own theory, because it wasn't really a theory. It was simply a toy model to show that realistic theories could exist. Bell was very excited to see Bohm's theory because he too believed the Von Neumann result. But, after learning Bohm's theory, he detailed exactly where Von Neumann's argument breaks down. He also investigated the non-locality of Bohm's theory and this led to Bell's inequality.

In conclusion, Bohm's theory is flawed, but it was known to be flawed by Bohm himself. It was only intended to be a guide to the way forward, and indeed it led to Bell's inequality, and Kochen-Specker's Theorem which place great constraints on the kinds of theories that could replace quantum mechanics.

I think it's unfortunate that nobody cares about the problems with quantum mechanics. Einstein, Bell, and Bohm were the last of the physicists who really cared about understanding how nature is. I miss those days, and wish we had those great men back.

reader Luboš Motl said...


1) I know how Bohmian mechanics is constructed very well, thank you
2) you probably meant the history of Bohmian mechanics, not construction, but I haven't discussed it at all, so my story of it couldn't have been "poor"
3) your history of Bohmian mechanics is totally defective because you completely omitted its original discovery - it was discovered with all the modern equations by Louis de Broglie in 1927, Bohm only later revived it and added some marketing
4) that Bohm would ever consider this picture is a legend
5) there are no "problems with quantum mechanics"
6) it is not true that people are not "acknowledging problems with quantum mechanics". Thousands if not millions of subpar physicists - not just laymen like you - do so every day, and this MIW paper is juust another example of this insane anti-quantum obsession by the subpar researchers.

reader Luboš Motl said...

Exactly. It's partly about the inability to account for complicated systems.

But our understanding why it's a wrong direction, Bill, must be much more intuitive. It's about some instinctive opinion about the "beauty" of the laws of physics.

It's analogous to construction of buildings. We have no trouble with modern materials, glass etc. (field theory, quantum probability amplitudes). These people want to construct everything out of things they know extremely well. Well, let's face it. They want to construct everything from piles of šit (classical mechanics). And they believe that all the new materials (quantum mechanics etc.) may be avoided if they accumulate a really large number of these piles of shit (many worlds) and if lots of insect will fly in between of them (interacting many worlds). But they just refuse to admit that someone else - like Nature Herself - could be using completely different materials (or ideas) to make the work done, and that this set of materials (or ideas) could actually be much superior.

reader David Brown said...

"The world just isn't a classical Newtonian clockwork!" This is an empirically valid statement. However, the world is also not a Lambda Cold Dark Matter Concordance Cosmological Model, according to Kroupa.
The Lambda CDM model is wrong for at least 3 reasons: MOND, the space roar, and the photon underproduction crisis. Something is wrong with the foundations of cosmology.

reader Mitchell Porter said...

Let me offer a minor exclusive to The Reference Frame: I suspect that I am ultimately the source of the Australian side of this research, because I had this idea years ago, and I have talked with the lead researcher many times, so I suspect I mentioned the concept to him during a visit to his office. I'm not claiming to have even written down an equation - just to have had the bare idea that the role of the pilot wave in Bohmian mechanics could be replaced by an inter-world interaction. I often appeal to this idea in discussion with Many Worlds advocates, when I complain about the nonsense and vagueness of what they say. I tell them, if you do insist on developing a Many Worlds theory, here is an example of how it could at least be mathematically and conceptually crisp. But I don't take it seriously as a physical theory.

reader Giotis said...

Off topic:

Tara Shears remark that String theory for experimentalists falls into the ‘not even wrong’ camp of theories make her ignorance manifest; experimentalists should stop commenting on cutting edge theoretical physics if they don’t have a clue of what they are talking about.

The fact that you are a physicist doesn't mean that you are entitled to have an opinion about things you don’t know.

reader Luboš Motl said...

Good you listened to it more comprehensively than I did - I didn't have the nerves... ;-)

reader Dilaton said...

Exactly: people who feel entitled to express (in particular strongly negative) opinions about things they have no (technical) clue about, are nothing but arrogant pompous their state of knowledge overreaching wannabes and fraudsters.

It is exactly this (unfortunately omnipresent these days) kind of agressive public trolling of people who have no clue what they are talking about, that drives me up the wall most!

And even less comprehensible is that laypeople who dont know better take these trolls serious, whereas what real experts say is "just another opinion". As if physics were driven by opinion like arts, literature, etc ...

reader Johannes said...

You say you can't _prove_ that there's no realist extension of quantum mechanics. What I find most striking is that so many people still insist on trying to find such a thing (despite so many theoretical and experimental constraints). In my view, being "non-realist" should be accepted as the central _feature_ of quantum mechanics, not a deficiency. It certainly has been the central _message_ of quantum mechanics, and with a little bit of stretch, it even allows making more sense of classical physics as well. (What I mean is, roughly speaking, that while classical mechanics is "realist" in the technical sense of the term, it doesn't have to be interpreted "realistically".)

reader Gene Day said...

It is preposterous to claim that today’s top physicists don’t care about understanding “how nature is”.
You are stuck in time and unwilling to learn better. The only problems with quantum mechanics are in your closed mind.

reader Justin said...

(2) Yes, you're correct, I did mean the history of the theory.

(6) Actually, I agree with you on this. I think it's unfortunate that there aren't too many heavyweights working on foundations of quantum mechanics. 't Hooft is probably the best physicist since Bohm to work on foundations, but I don't like his research direction at all. I think he completely ignores the work of Bohm.

(5) Actually, I agree with you on this as well. Quantum mechanics is a gadget for predicting the outcomes of experiments. As a working algorithm to predict distributions of experimental results, quantum mechanics is -- at least so far -- perfect. Bohm acknowledged this, but also acknowledged that it doesn't describe the reality of a single experimental result, it only describes distributions of repeated experiments. So, quantum mechanics while correct as an algorithm, is not a true fundamental theory.

(3) True, but it is well known that Bohm rediscovered De Broglie's work entirely on his own, and then made striking contributions of his own.

reader John Archer said...


"[QM] doesn't describe the reality of a single experimental result, it only describes distributions of repeated experiments. So, quantum mechanics while correct as an algorithm, is not a true fundamental theory."

Firstly, I'm not a physicist, so maybe I have misunderstood you. But I'll take the risk.

For whatever reasons, as much as one might balk at the idea of QM being essentially probabilistic in this way, it seems to me it that that doesn't mean that Nature itself isn't. But that seems to be precisely what you're suggesting by the above — that Nature is not fundamentally probabilistic.

I'm interested to know what criterion you are using to claim that, if indeed you are.

reader Dilaton said...

Hi Lumo, sorry for the slight off-topic:

You know, my favorate approach to QM interpretations is that it needs non (=shut up and calculate) as QM just works. Also, most quantum foundation discussions are not interesting to me, as I always think "dont repair it if it is not broken" ...
But could you say in a short remark what you think about Arnold Neumaier's thermal point of view?

As you can see from this discussion, Gerard t'Hoft asked him too what it is about ...

reader Ruth Kastner said...

Some of these dismissals of 'realism' about QM seem to be based on a particular narrow but very common notion of what' realism' means--in particular the idea that it means local and./or beable-type realism which is basically classicality. For purposes of discussion, one could call this 'pseudo-classical realsim'. I offer a realist interpretation that does not involve locality or classical notions (such as Einsteinian 'elements of reality' or beables). So I don't think that the only choices are 'antirealism' or 'pseudo-classical realism' -- rather, we need to broaden our notion of what it means for QM to describe reality. Reality may not be local or classical, but QM can stilll tell us something interesting about it. See eg my Cambridge lecture (availabe on youtube) for what such an interpretation would be like.

reader Luboš Motl said...

No, Ms Kastner, you are absolutely deluded about every single point you were trying to make.

What the evidence refutes is not just a narrow subclass of realist theories. The evidence rules out any realist theory in the most general sense of the word.

You are also totally confused about the words "realist" and "local". These two adjectives are completely independent – after all, the most characteristic "realist" theory, Newton's classical mechanics, was surely nonlocal as it involved action at a distance – and it's the "realism", and not "locality", which is the principle abandoned by the quantum revolution.

Preemptively: Please avoid repeated publication of comments with nothing else than these basic delusions of yours about modern physics you've already written down in your comment above, otherwise I will immediately blacklist you.

reader RAF III said...

Lubos - That was awesome!!! How did you do it?

reader John Archer said...

I have a theory on that!

Luboš keeps a secret, well-thumbed copy of Dale Carnegie's 1936 classic under his pillow.

He's currently putting it to a thorough empirical testing. :)

Whaddya reckon? Am I close?

Tee hee.

reader Luboš Motl said...

Dear Ms Kastner, thanks for your visit. You don't have any special registration with this website. You only registered with DISQUS which you used for the Atlantic, Nautilus, and 2 more journal servers, and I obviously can't do anything about that global registration.

reader Luboš Motl said...

Dear John and RAF, I would appreciate if you explained me what was awesome. Probably due to my cultural detachment, I have no clue what's going on. Is she famous in some way? Or did she travel through a time machine? Or what am I missing?

reader RAF III said...

Lubos - She's a crackpot 'philosopher of science', on a par with e.g. Maudlin, attempting to rejuvenate the transactional interpretation.
You somehow made her go away, and of her own accord; something I have never seen happen and have never experienced myself.
Are you a Jedi? Have you gone to the dark side? Were you bitten by a radioactive spider?
Please teach me your ways!

reader Luboš Motl said...

Thanks, RAF. Yup, I ran into her name when I was writing about the "transactional interpretation" which is some set of illogical comments about the acuasal (past-rewriting) things promoted by a guy named Cramer, whom I didn't really know himself, and she "inherited" this "interpretation" because she's relative. But do normal Americans interested in science know her?

Some people love to pump lots of comments. Some people are more shy, thank God, otherwise one would get overwhelmed by the amount of pseudoscientific spam one has to deal with. So she's among the more shy ones, I guess.

reader W.A. Zajc said...

I completely agree with your extended metaphor Lubos, even if it's one I would not want to think about too closely, particularly before a meal ;-)

reader John Archer said...

I was just messing around. Apologies for my late reply here.

"...what am I missing?"

Haha! Nothing as far as I can tell. The bullet went neatly straight through, that's all — no miss there. And now no Ms! :)

That reminds me of the mystery when as a 13-year old I shot a stationary rabbit at about 50 yards. The rabbit just sat there staring back at me. "Fcuk me!" I thought, "I missed!" But I'm a pretty good shot, and anyway it was a twelve bore shotgun, not a rifle, so even if I'd been a lousy shot I'd have probably got it in any case. I couldn't make it out — why didn't it bolt at the bang? "That rabbit's got some nerve," I thought. Then a few seconds later, just like in the cartoons, it slowly keeled over sideways stone dead. I got it straight through the brain. Mystery solved.

The thing is, over time I came to regret I'd done it, and a few other similar things. There was no need for any of them. They were no threat. I'd now much rather I'd missed and watched it hop away. A loud bang to make it jump should have been enough sport for me.

reader Marcus Arvan said...


This type of interpretation is not entirely new. I defended a similar, many-interacting-worlds interpretation (in a simulation-theory context) in two peer-reviewed articles dating back to 2013. See and

reader Michael Arthur Bucko said...

I love your blog, Sir.

reader Alfonso De Miguel said...

Think about two intersecting fields that vary (expanding and contracting) periodically. Their mutual interaction comes from their periodical variation.

reader zarzuelazen said...

You've written a strong critique of MIW. I'd be interested to hear your critiques of other 'realist' interpretations.

David Deutsch argued strongly for MWI (Many-Worlds-Interpretation) , explained in his book 'The Fabric Of Reality'. Other physicists seem to think MWI is the best realist option, in that it preserves locality and determinism. What is so bad about Many-Worlds Interpretation?

reader Tahlia Jowett said...

Bob Deutsch suggested highly for MWI (Many-Worlds-Interpretation) , described in his guide 'The Material Of Reality'. Other physicists seem to think MWI is the best realist choice, in that it maintains area and determinism. What is so bad about Many-Worlds Interpretation?

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