Problems with Many Worlds Interpretation

[Samshorn]

Deutsch is trying to meet certain criticisms of the MWI to make it more acceptable. That is not a requirement of the MWI being a valid interpretation of quantum mechanics, it relates to whether or not it can be regarded as a preferred interpretation.

I think you're mistaken about that. Here's a little excerpt from a discussion between Deutch and Paul Davies (reproduced in the book "The Ghost in the Atom"):

Deutch: "When Everett first put forward his interpretation, he believed that it was a pure interpretation in the technical sense of the word. In other words, that the physical predictions of quantum theory under his system were precisely identical with those under any other system. Now, I believe that this is not so, and I have recently done some work trying to elaborate the exact experimental difference between the Everett and the conventional 'interpretations'. I now have to say 'interpretations' in quotes because I believe that there are actually different formal structures for quantum theory."

Davies: "So we're talking, not about two different ways of looking at the same theory, but two completely different theories?"

Deutch: "Yes..."

So I think you have not really understood Deutch's position - and I would argue that the same applies to other prominent advocates of MWI. It's fairly clear that the explicitly unitary version of MWI (which is all anyone cares about) is a distinct theory from QM.

I can very easily give an MWI interpretation that is as valid and consistent with quantum mechanics as CI-- we simply interpret all closed systems as having a Hamiltonian and a wave function... that evolves via the Shroedinger equation. Then we just do everything that CI does when we refer to decohered subspaces of that closed system...

Your first sentence describes the unitary (top down) version of MWI, but your second sentence describes bottom up version of MWI. It isn't legitimate to claim unitarity from the first version and consistency with QM from the second version. I know you think the two versions are equivalent, and I've tried to explain in various ways why they are not equivalent, and I've cited at least one prominent advocate of MWI who contends they are not equivalent... but none of this seems to make any impression on you. Maybe we can make some progress by examining this statement:

...we simply interpret all closed systems as having a Hamiltonian and a wave function, even if we can't stipulate either, that's why it's an interpretation and not a theory, but note CI doesn't stipulate them either so we have changed nothing but our way of thinking...

I would say both clauses of that sentence are wrong. First, I think it's wrong to say an idea can qualify as an interpretation of a theory involving Hamiltonians and initial conditions even if that idea is incapable of ever identifying the applicable Hamiltonian or initial conditions. This gets us back to our fundamental difference over whether or not an interpretation is required to actually make some kind of rational sense. Second, I think it's wrong to say that CI likewise fails to make such an identification... the whole point of Bohr's insistence on the need for the measuring instruments to be treated as classical objects is because he recongnized that without this we just have "one hand clapping", and can never hope to identify the Hamiltonian and initial conditions and potential functions for any specific physical situation. CI is a (relatively, though not entirely) well-defined interpretation of QM as a theory that describes how a quantum system interacts with a classical system. This is what gives CI whatever degree of well-definedness it possesses. But MWI lacks this.

An interpretation is not a theory, it is merely a way to achieve some personally satisfying degree of cognitive resonance while a theory is being used.

We strongly disagree about this. As I said before, every scientists and almost every philosopher of science I know would not accept such a lax definition of "interpretation" for a physical theory - and furthermore, even under this (to me) ridiculously lax definition, MWI STILL doesn't qualify as an interpretation, unless you go on to define "cognitive resonance" to mean "whatever anyone thinks is cognitive resonance". And even FURTHERmore, if we were to accept all these "whatever floats your boat" (WFYB) definitions, it would surely be permissible to criticize "interpretations" in this context.

Above all, we must recognize that interpretations are not unique, and we should never expect there to be a "correct" interpretation of any physical theory.

Of course interpretations are not unique, but I would differ with the "above all", because I think above all is the requirement for the concept of an interpretation to be meaningful and well-defined. Obviously if we were to apply the WFYB definition of "interpretation", then it would never even occur to anyone that they might be unique. The interesting point is that even with meaningful and well-defined interpretations it turns out there is non-uniqueness. But we wouldn't be able to see this interesting point if we held to the WFYB definition of "interpretation".

That's not what I mean by "mean". The example I gave above is how x(t) emerges from classical trajectory calculations...So interpretations are simply not what you ask them to be.

I don't see the disagreement. What you described there is exactly what I described, in terms of the contrast between operational definitions of x and t versus the abstract concepts of time and three-dimensional space. If there is any difference in our views about this, I guess it's that I think there is a fairly meaningful and well-defined correspondence between the operational definitions of x & t and the conceptual model of 3D space and time, and that this degree of correspondence between operational variables and concepts is lacking in MWI.

...that same criticism is leveled by every person who rejects a given interpretation.

I don't see it as a criticism of one interpretation versus another, I see it as an aspect of interpretations in general, i.e., they are a way of placing something within some conceptual context, and they tend not to be regarded as satisfactory unless the conceptual context is one with which people are already comfortable.

MWI enthusiasts say CI is backward-looking because it cannot accept that reality might transcend our ability to perceive it...

I don't think that's true. The rap against CI hasn't traditionally been that it is reactionary, but rather that it is wooly and adventurous and even quasi-mystical. It is an exceptional interpretation precisely because it denies the quo ante categories. Those are the features that repell people, and that motivate things like MWI, which sees itself as dispensing with Bohr's mystical dualism and tries to eliminate "those damned jumps" and restore the classical basis of a deterministic continuous differential equation. There's nothing unclassical about imagining infinitely many "sub-worlds". It's extravagant, but not unclassical. So I would still say that MWI is a (so far unsuccessful) reactionary idea for an interpretation of QM in classical terms, and I think most advocates of MWI would actually agree with this, which they regard as its motivation - eliminating Bohr's mystical dualism.

 

[Ken G]

I think you're mistaken about that. Here's a little excerpt from a discussion between Deutch and Paul Davies (reproduced in the book "The Ghost in the Atom"):

But that's just what I meant when I said "In short, Deutsch is joining those who try to argue that MWI is objectively better than CI because it inspires a set of postulates that are more powerful than CI, and might even make different predictions"-- Deutsch doesn't think MWI is an interpretation of QM, he thinks it is a new theory that is more powerful, that is how he tries to sell it. I don't say that's wrong, I say I am unconvinced by the argument. To me, the claims that MWI (or Bohm) makes different predictions are very flimsy. They might be true in some formal sense, but physical theories are idealized anyway, so the distinctions are lost in the idealizations.

So I think you have not really understood Deutch's position - and I would argue that the same applies to other prominent advocates of MWI.

I think I do understand Deutch's position, but it doesn't matter-- since the MWI I refer to is an interpretion of quantum mechanics, I don't view Deutsch as the oracle of MWI, I view him as a proponent of some new theory that has no observational support.

It's fairly clear that the explicitly unitary version of MWI (which is all anyone cares about) is a distinct theory from QM.

Unless Deutsch is wrong, and Everett was right. I don't know the technical details Deutsch is talking about, but they may represent certain philosophical positions that go beyond simple unitarity. I'd have to see Deutch's arguments for why you cannot simply take CI and treat the renormalized amplitudes of a "collapsed" wavefunction as conditional on the experiences of the observers, and embed them into larger unnormalized wavefunctions that are not so conditioned, and retain unitarity via the complicated coherences of the full wave function that are not represented in the mixed-state projection onto the subsystem. That seems like it would work just fine, if you could ever actually write the wavefunction of the full system and evolve it according to the Schroedinger equation.

I know you think the two versions are equivalent, and I've tried to explain in various ways why they are not equivalent, and I've cited at least one prominent advocate of MWI who contends they are not equivalent... but none of this seems to make any impression on you.

You have claimed they are different, and you have cited an authority who sees them as different, and you have claimed that anyone who holds to MWI is basically an idiot. In total, I find that set of arguments unconvincing, as do many.

First, I think it's wrong to say an idea can qualify as an interpretation of a theory involving Hamiltonians and initial conditions even if that idea is incapable of ever identifying the applicable Hamiltonian or initial conditions.

I understand you think that's wrong, yet this is quite a typical assumption for rationalistic interpretations of any physics theory. The rationalistic interpretation holds that the universe must have both a Hamiltonian and some initial conditions, because the theory says a universe without a Hamiltonian and initial conditions would not know how to evolve in time, yet we all know these could never be stipulated in detail. This is quite consistent with many other interpretations-- Newton thought the universe needed forces and initial conditions, even though he knew quite well they could not be stipulated either. So it's just not true to object to an interpretation on the grounds that it holds the reality cannot be stipulated. For my own part, I object to imagining that any of those things exist in the reality, but it is just fine to say they exist in the intepretation of the theory, even though they cannot be stipulated.

This gets us back to our fundamental difference over whether or not an interpretation is required to actually make some kind of rational sense.

Now you are equating "makes rational sense" with "is able to be completely stipulated." Yet I would argue that any claim that the elements of any theory could be completely stipulated is what does not make rational sense. Give me any interpretation of any physics theory that you think allows a complete stipulation of the elements of that theory.

Second, I think it's wrong to say that CI likewise fails to make such an identification... the whole point of Bohr's insistence on the need for the measuring instruments to be treated as classical objects is because he recongnized that without this we just have "one hand clapping", and can never hope to identify the Hamiltonian and initial conditions and potential functions for any specific physical situation.

No, Bohr knew quite well that we would never hope to do that, regardless of the classical treatment of the measuring devices. How is treating the instruments as classical going to allow the Hamiltonian of any subsystem to be completely specified? That never happens, in any interpretation, physics theories always need idealization to be useful.

CI is a (relatively, though not entirely) well-defined interpretation of QM as a theory that describes how a quantum system interacts with a classical system. This is what gives CI whatever degree of well-definedness it possesses.

CI is completely nondescript about the interection between the quantum system and the classical system! That's what people don't like about it. Personally, that doesn't bother me-- it simply chooses not to try to describe that interaction, beyond the usual vagaries of "decoherence."

And even FURTHERmore, if we were to accept all these "whatever floats your boat" (WFYB) definitions, it would surely be permissible to criticize "interpretations" in this context.

One can criticize interpretations, but only on pedagogical grounds. Not that they are invalid, if they suffice for someone who is adept in the theory.

The interesting point is that even with meaningful and well-defined interpretations it turns out there is non-uniqueness. But we wouldn't be able to see this interesting point if we held to the WFYB definition of "interpretation".

I think your characterization of "well defined" is artificial, it seems to basically boil down to your favored interpretations. I don't think "well defined" is a useful word with interpretations, they're all pretty vague.

I don't see the disagreement. What you described there is exactly what I described, in terms of the contrast between operational definitions of x and t versus the abstract concepts of time and three-dimensional space. If there is any difference in our views about this, I guess it's that I think there is a fairly meaningful and well-defined correspondence between the operational definitions of x & t and the conceptual model of 3D space and time, and that this degree of correspondence between operational variables and concepts is lacking in MWI.

Yes, I would not agree on that well-defined correspondence. Indeed, someday we may find that the operational definition of x & t is continuous (we already have that), yet the best conceptual model of 3D space and time is discrete. What would that mean, that a well-defined interpretation is suddenly not well defined? It was always not well defined, I could interpret classical mechanics right now as being a theory for a discrete spacetime and still do classical mechanics just fine, you couldn't even tell.

I don't see it as a criticism of one interpretation versus another, I see it as an aspect of interpretations in general, i.e., they are a way of placing something within some conceptual context, and they tend not to be regarded as satisfactory unless the conceptual context is one with which people are already comfortable.

Yes, but there can be a tradeoff, as there is with CI and MWI. CI connects better with empirical experience, MWI connects better with rationalistic and analytic experience.

I don't think that's true. The rap against CI hasn't traditionally been that it is reactionary, but rather that it is wooly and adventurous and even quasi-mystical.

Lots of people criticize CI for being reactionary. It is the same as the mysticism-- it is mystical because it insists on connecting reality to classical experience (empiricism), but empiricism is reactionary in the 1900s (witness the string theory phenomenon).

There's nothing unclassical about imagining infinitely many "sub-worlds". It's extravagant, but not unclassical.

I agree, I would say it is un-empirical more so than un-classical. But I view the empiricism as more central to CI than the classicism. Classicism is more the crux of Bohmian interpretations.

 

[juanrga]

The whole point of MWI is to dispense with the projection postulate, and to argue that the -approximate- appearance of QM with a projection postulate emerges purely from unitary evolution, taking decoherence and a bunch of other things into account - but NOT a projection postulate. The mathematics of decoherence is totally different from the mathematics of projection, and the correspondence is acknowledged even by proponents of MWI to be only approximate (i.e., close enough for all practical purposes). The off-diagonal terms of the density matrix are never exactly zero with decoherence. MWI based on the postulate of unitary evolution most definitely does not include a projection postulate - which is why it's consistency with the empirical content of quantum mechanics is not established (and, I argue, can never be established).

I agree with almost all what you say. I would only emphasize two points:

First, the 'mathematics' behind decoherence are suspicious. The non-unitary evolutors do not follow from doing approximations to unitary evolutors, but by ad-hoc substitution of groups by semigroups. Van Kampen liked to call this kind of derivations «mathematical funambulism».

Second, the so close-enough-for-all-practical-purposes mantra (Penrose uses the acronym FAPP in a delicious way to criticize decoherent people as Zurek) works when one focuses in typical non-Markovian, second order coupling evolutors, because experience in this regime is so broad that allows one to apply the correct equations in the correct way using certain ad-hoc procedures and rules.

Outside of this simple regime, nobody knows how to derive/apply the equations or when certain approximations are valid or are not, due to the lack of underlying systematic methods.

 

[Ken G]

Van Kampen liked to call this kind of derivations «mathematical funambulism».

The problem with this criticism is that all of physics is mathematical funambulism, as it has always been. Physics borrows from mathematics, but physics is not mathematics.

Second, the so close-enough-for-all-practical-purposes mantra (Penrose uses the acronym FAPP in a delicious way to criticize decoherent people as Zurek) works when one focuses in typical non-Markovian, second order coupling evolutors, because experience in this regime is so broad that allows one to apply the correct equations in the correct way using certain ad-hoc procedures and rules.

Yet all of physics is ad-hoc procedures and rules. What's the problem? Which physics entity is not ad-hoc, the properties of what element of physics follows directly from that element, in some kind of obvious or logical way?

Outside of this simple regime, nobody knows how to derive/apply the equations or when certain approximations are valid or are not, due to the lack of underlying systematic methods.

But since when has physics ever been about underlying methods? The methods of physics are clear enough: observe, guess, observe some more, theorize, observe, unify, lather, and repeat. Nothing underlying at all, it's all right there on the surface. Yes it's amazing that this works as well as it does, but that doesn't prove there is something underlying it, that's essentially just personal philosophy, or even wishful thinking.

 

[juanrga]

The problem with this criticism is that all of physics is mathematical funambulism, as it has always been. Physics borrows from mathematics, but physics is not mathematics.

Here you confound his «mathematical funambulism» with the general lack of mathematical rigor that you can find in physics except, probably, in mathematical physics. Van Kampen did not confounded both concepts, neither I do.

Yet all of physics is ad-hoc procedures and rules. What's the problem? Which physics entity is not ad-hoc, the properties of what element of physics follows directly from that element, in some kind of obvious or logical way?

It is not true that all of physics are ad-hoc procedures and rules. Large parts of physics are axiomatized or are in the process of being axiomatized.

But that was not the point, the point is that the FAPP-mantra of the decoherent community fails almost always when one looks for the details, as Penrose knows. Their so-called FAPP is really a FAPP-where-I-known-the-correct-answer-before.

But since when has physics ever been about underlying methods? The methods of physics are clear enough: observe, guess, observe some more, theorize, observe, unify, lather, and repeat. Nothing underlying at all, it's all right there on the surface. Yes it's amazing that this works as well as it does, but that doesn't prove there is something underlying it, that's essentially just personal philosophy, or even wishful thinking.

I emphasized, in bold-face, that they lack systematic methods, a word that you have completely avoid when engaging in an useless discussion.

Useless, because when I was referring to the methods I was referring to the specific procedures associated to a given theory as decoherence (of course, the concept can be applied to a whole discipline e.g. "methods of thermodynamics" is a classic).

I was not referring to the general concept of scientific methods (what it seems that you call the «methods of physics»).

 

[Ken G]

Here you confound his «mathematical funambulism» with the general lack of mathematical rigor that you can find in physics except, probably, in mathematical physics. Van Kampen did not confounded both concepts, neither I do.

I see, you imagine good funambulism, and bad funambulism, based around your own philosophical preferences. All the same, countless numbers of physics theories use approaches that do not stem directly from any postulates. It is much more common for physics theory to be like that, just pick up any journal in which physics theory is being used to analyze some phenomenon that doesn't fit nicely into one of the boxes that sound like course titles. One random example might be the radiative reaction force, and consider for example the funambulism Feynman mentions in regard to that-- and that's just classical electrodynamics, one of the simplest theories we have. Never mind the divergences of QED! My question is: why do people seem to expect quantum mechanics to work in a more pure or mathematical way than all the rest of the theories of physics? Why should decoherence in quantum mechanics look totally different from something like line broadening mechanisms in a dense plasma, where note that the latter is perfectly rife with FAPP-inspired funambulism?

It is not true that all of physics are ad-hoc procedures and rules. Large parts of physics are axiomatized or are in the process of being axiomatized.

Some parts yes, but not "large" parts. Very little physics works like that, by which I mean, if you go down the hall in a physics department and look at the posters of their research. They are not going to look like mathematical theorems based on a set of postulates!

One of the most obvious examples of my point is the need for idealizations. There is never a formal treatment of what is being neglected, we just say "we'll neglect X, Y, and Z", and let our results tell us if we can get away with that. This even applies to something as simple as the Coulomb logarithm, another example of mathematical funambulism that is nevertheless used all the time and with no apology because that's just what physicists do, it would be hard to go to work without being allowed to do that.

But that was not the point, the point is that the FAPP-mantra of the decoherent community fails almost always when one looks for the details, as Penrose knows. Their so-called FAPP is really a FAPP-where-I-known-the-correct-answer-before.

I can agree that reasoning to produce a desired outcome is not the same thing as a mathematical derivation of said result. My point is merely that physics does FAPP all the time, it's nothing new, and it's not an inappropriate way to do physics unless it is sold as something else.

I emphasized, in bold-face, that they lack systematic methods, a word that you have completely avoid when engaging in an useless discussion.

And what do you think "systematic" means? There are vast arrays of journals which are loaded with systematic FAPP-type analyses, it is more or less what research is. One might try to argue that the problem you refer to is that FAPP should not appear at the fundamental level of pure theory, but it's not at all clear that anyone who is using FAPP with decoherence is claiming they are doing anything different from standard physics-- trying to understand some phenomenon using effective treatments, where the "system" is essentially time-honored trial and error.

Useless, because when I was referring to the methods I was referring to the specific procedures associated to a given theory as decoherence (of course, the concept can be applied to a whole discipline e.g. "methods of thermodynamics" is a classic).

Yes, it can be applied to thermodynamics, and is. So what is so terrible about applying it to the decoherence in quantum mechanics? Thermodynamics is some different kind of physics than quantum mechanics? I just think some people start imagining that physics is some new and different field when they get into fundamental new theories built around quantum mechanics, and I see no justification. The methods of physics are just like those used in thermodynamics-- and are rife with FAPP, it's just not always admitted.

I was not referring to the general concept of scientific methods (what it seems that you call the «methods of physics»).

Well, perhaps you have something more specific in mind where you object to the FAPP concept, but decoherence is not a nice canned field of physics, it is one of those messy, tricky and evolving fields, like quantum thermodynamics. FAPP would seem to have its place, that's all I'm saying.

 

[juanrga]

I see, you imagine good funambulism, and bad funambulism, based around your own philosophical preferences.

You 'see' stuff that nobody said. Also I was not appealing to «philosophical preferences». I am discussing in a physics forum and my criticism of both MWI and decoherence is purely technical.

All the same, countless numbers of physics theories use approaches that do not stem directly from any postulates.

All the established basic theories of physics follow from postulates: GR, QM, thermodynamics, mechanics, SM...

It is much more common for physics theory to be like that, just pick up any journal in which physics theory is being used to analyze some phenomenon that doesn't fit nicely into one of the boxes that sound like course titles. One random example might be the radiative reaction force, and consider for example the funambulism Feynman mentions in regard to that-- and that's just classical electrodynamics, one of the simplest theories we have.

You must be misreading him. Feynman never said that CED lacks postulational basis. Feynman said that the Maxwell-Lorentz formulation of CED fails when is applied to certain kind of problems.

Feynman and Wheeler corrected this defect of the old formulation in their AAAD formulation of CED. For instance, in their new formulation a single particle does not radiate and thus lacks pre-accelerations and other unphysical stuff traditionally associated to the Maxwell-Lorentz formulation. Of course, they present the set of basic postulates for their formulation of CED.

Never mind the divergences of QED! My question is: why do people seem to expect quantum mechanics to work in a more pure or mathematical way than all the rest of the theories of physics? Why should decoherence in quantum mechanics look totally different from something like line broadening mechanisms in a dense plasma, where note that the latter is perfectly rife with FAPP-inspired funambulism?

QED, as rest of QFT, has a postulational basis. The divergences only arise when you forget that QED is an effective field theory and you try to apply it outside its range of validity. It is now acknowledged that the divergences of QED are eliminated in more fundamental theories that introduce a kind of cut-off, beyond the which QED does not apply.

Quantum mechanics, of course, has a postulational basis. Just open a standard textbook to see the postulates.

I can agree that reasoning to produce a desired outcome is not the same thing as a mathematical derivation of said result. My point is merely that physics does FAPP all the time, it's nothing new, and it's not an inappropriate way to do physics unless it is sold as something else.

The point was not reasoning vs. mathematical derivation, but mathematical derivation vs. «mathematical funambulism».

The rest of your discussion also avoids my main points and pretend to debate about stuff that I have never said. Whereas you repeat mistakes corrected (again you confound the specific methods associated to a discipline as thermodynamics with the general methods of science: the so-called scientific methods).

 

[Ken G]

I am discussing in a physics forum and my criticism of both MWI and decoherence is purely technical.

And I'm questioning the validity of that objection. All kinds of advances are made in physics, literally every day, that involve FAPP thinking, and which all could be objected to on "technical" grounds. So what? That claim by itself is not a valid objection to doing FAPP thinking, one would need to be able to argue on technical grounds that what is being argued is FAPP is actually not FAPP. Show where it leads to a demonstrably wrong conclusion in general practice, for example.

All the established basic theories of physics follow from postulates: GR, QM, thermodynamics, mechanics, SM...

Sure, but most of physics research is not just one of those. The vast majority of all physics applications in actual research are going to go beyond these theories, or there would be no need to do the research in the first place. The place where the research goes beyond the postulates will generally be covered in the early stages of the paper, where the unique assumptions of that paper are outlined.

You must be misreading him. Feynman never said that CED lacks postulational basis. Feynman said that the Maxwell-Lorentz formulation of CED fails when is applied to certain kind of problems.

One defines QED (or any mathematical theory) by its postulates, so the issue is not whether it lacks postulational basis, the issue is whether or not one can just stick to those postulates to use QED in physics. The answer is that one cannot-- one encounters divergences that are handled by the kinds of funambulism that physics is impossible without.

Feynman and Wheeler corrected this defect of the old formulation in their AAAD formulation of CED. For instance, in their new formulation a single particle does not radiate and thus lacks pre-accelerations and other unphysical stuff traditionally associated to the Maxwell-Lorentz formulation. Of course, they present the set of basic postulates for their formulation of CED.

It is not uncommon for new theories to correct the funambulisms of prior theories. What is quite rare is for new theories to lack their own funambulisms when applied in practice.

QED, as rest of QFT, has a postulational basis. The divergences only arise when you forget that QED is an effective field theory and you try to apply it outside its range of validity.

Translation: the divergences only arise when you try to do physics. I realize this-- that's what I meant that physics is not mathematics. All theories of physics are effective theories.

It is now acknowledged that the divergences of QED are eliminated in more fundamental theories that introduce a kind of cut-off, beyond the which QED does not apply.

And those more fundamental theories have no issues of their own?

Quantum mechanics, of course, has a postulational basis. Just open a standard textbook to see the postulates.

Again, all physics theories are defined by their postulates, so they all have a postulational basis. That has nothing to do with what I'm talking about, I'm talking about doing physics. We can agree that decoherence is not yet something that can be called a physics theory, it is a way of understanding what is happening in the world that helps us see why quantum mechanics (the mathematical theory) applies, and how to apply it. In short, without the FAPP of decoherence thinking, one cannot do physics with quantum mechanics and have any idea how it should apply to the real world. The funambulism there is what is needed to make the theory make sense, and there is nothing unusual about that state of affairs in physics. That doesn't mean Penrose and others shouldn't try to find a better more fundamental theory that eliminates the need for that particular brand of funambulism, but of course any such new theory will have its own issues, and funambulisms, and hence the need for yet newer theories. Such is physics, thoughout all its history. One does not need to reject FAPP approaches to press forward on new theories and new formulations, the two work perfectly well hand-in-hand.

 

[juanrga]

And I'm questioning the validity of that objection.

Yes, by systematically ignoring the technical remarks made and trying to discuss the issue at some philosophical level.

Sure, but most of physics research is not just one of those. The vast majority of all physics applications in actual research are going to go beyond these theories, or there would be no need to do the research in the first place. The place where the research goes beyond the postulates will generally be covered in the early stages of the paper, where the unique assumptions of that paper are outlined.

Of course, but don't forget that the new theories need to be backward compatible with the previous one. Precisely, the main fiasco of the MWI is that is not compatible with QM.

One defines QED (or any mathematical theory) by its postulates, so the issue is not whether it lacks postulational basis, the issue is whether or not one can just stick to those postulates to use QED in physics. The answer is that one cannot-- one encounters divergences that are handled by the kinds of funambulism that physics is impossible without.

I am not sure if I would reply to this, correcting what you say, or if merely would notice that I was writing about CED (not about QED) in the paragraph that apparently you are replying

It is not uncommon for new theories to correct the funambulisms of prior theories. What is quite rare is for new theories to lack their own funambulisms when applied in practice.
Translation: the divergences only arise when you try to do physics. I realize this-- that's what I meant that physics is not mathematics. All theories of physics are effective theories.

In this part you reply a paragraph from mine where I have not used the word funambulism. Why? Because, as remarked before, the use that you give to the term is not the use given either by van Kampen or by me.

You can discuss with yourself about your own meaning/usage of the words, but I am not interested.

And those more fundamental theories have no issues of their own?

Of course that they have. I am convinced that the perfect theory or TOE exists only in the imagination of some naive physicists, but again that was not the point.

The point is that those more fundamental theories lack issues of the older and less-fundamental theories that have improved/corrected.

This is not the case with MWI. MWI does not improve/correct QM, but MWI is unable to explain what QM explains so well since 100 years ago. This is why MWI is considered nonsense and useless, as many posters have said to you before.

Again, all physics theories are defined by their postulates, so they all have a postulational basis.

No exactly. String theory (and specially M-theory) lacks axiomatic foundations because, as even its more fierce proponents agree, nobody knows still what the theory is. MOND theory also lacks axiomatic foundation, at least in its original Milgrom form, and would be best considered an empirical theory.

That has nothing to do with what I'm talking about, I'm talking about doing physics. We can agree that decoherence is not yet something that can be called a physics theory, it is a way of understanding what is happening in the world that helps us see why quantum mechanics (the mathematical theory) applies, and how to apply it. In short, without the FAPP of decoherence thinking, one cannot do physics with quantum mechanics and have any idea how it should apply to the real world. The funambulism there is what is needed to make the theory make sense, and there is nothing unusual about that state of affairs in physics. That doesn't mean Penrose and others shouldn't try to find a better more fundamental theory that eliminates the need for that particular brand of funambulism, but of course any such new theory will have its own issues, and funambulisms, and hence the need for yet newer theories. Such is physics, thoughout all its history. One does not need to reject FAPP approaches to press forward on new theories and new formulations, the two work perfectly well hand-in-hand.

Here you continue using terms in an ambiguous non-technical way and continue confounding stuff.

Decoherence, as a physical phenomenon, is real. I do not object that. But what people as Zurek usually call decoherence theory is an instance of what van Kampen calls mathematical funambulism and what Penrose criticizes as non-serious.

At the same time, QM and extensions of it are genuine physical theories, whereas MWI is a collection of internally-inconsistent 'theories' that cannot reproduce know phenomena. Enough references were given.

 

[Ken G]

Yes, by systematically ignoring the technical remarks made and trying to discuss the issue at some philosophical level.

What technical remarks? I saw none, only claims that they exist. In the absence of any actual technical issues around flaws in the descriptions of decoherence, the discussion is already at a more conceptual level.

Of course, but don't forget that the new theories need to be backward compatible with the previous one. Precisely, the main fiasco of the MWI is that is not compatible with QM.

Many theoretical physicists that I have been exposed to are proponents of MWI, so I can hardly intepret that as evidence that it is not compatible with QM. I guess your reasoning there must be too "technical" for them to understand. But you might find that neither Stephen Hawking nor Roger Penrose agree with your technical objections: in the Wiki on MWI, Hawking's opinion is quoted as saying that MWI is trivially a possible interpretation of QM, but he doesn't think interpretations can really tell us reality (which is my own view as well), and Penrose is purported to agree with Hawking that QM applied to the universe implies MW, but the Wiki says that "Penrose considers the current lack of a successful theory of quantum gravity negates the claimed universality of conventional QM." In other words, MW is QM, but the "technical" problem with both is the same problem. I'm afraid that all makes more sense to me than any of the arguments you've presented so far, but perhaps you haven't made your strongest case yet.

The point is that those more fundamental theories lack issues of the older and less-fundamental theories that have improved/corrected.

No, the point is that the more fundamental theories make different predictions that work. That is all that physicists are interested in, and funambulism comes with the territory. I agree that mathematical inconsistencies are often signposts to the need of new theories, but that only justifies the search for new theories, not the way you used it: to criticize solid physics on the grounds that it is not mathematically closed. Physics has never been that. All physics theories encounter difficulties in their application that the practicing physicist must navigate in many clever yet purely "effective" ways, that is the art of doing physics.

This is not the case with MWI. MWI does not improve/correct QM, but MWI is unable to explain what QM explains so well since 100 years ago. This is why MWI is considered nonsense and useless, as many posters have said to you before.

Yes, many posters have made that claim, and failed to justify it as completely as you have. I prefer to believe Hawking and Penrose than those posters. For my own part, the valid objections I see to MWI are primarily philosophical, and appear when people lose sight of the differences between theories, interpretations of theories, and claims about reality. That is the valid landscape for discussing the various interpretations, not vague allusions to problems that are apparently "too technical" to even discuss!

No exactly. String theory (and specially M-theory) lacks axiomatic foundations because, as even its more fierce proponents agree, nobody knows still what the theory is.

Then it is not actually a theory at all, in the literal sense. Your argument here is apparently that theories don't need to be defined by their postulates if someone hangs the label "theory" in the phrase "string theory"! No, "string theory" is just a term, it doesn't mean anything. Theories are still defined by their postulates.

MOND theory also lacks axiomatic foundation, at least in its original Milgrom form, and would be best considered an empirical theory.

And what defines an "empirical theory"? Empirical postulates! You can't have a theory without postulates, they just might not be mathematically closed, in the sense that everything you do with the theory stems directly from the postulates. I already mentioned that this is generally true of physics-- it is quite generally not mathematically closed, it is wide open, and physicists do all kinds of things starting from the basic theories, some that don't pan out at all, others that are effective at understanding some phenomenon in a way that does not follow strictly from any set of postulates of some theory, but rather require additional assumptions that are not laws.

Decoherence, as a physical phenomenon, is real. I do not object that. But what people as Zurek usually call decoherence theory is an instance of what van Kampen calls mathematical funambulism and what Penrose criticizes as non-serious.

Your argument has become internally inconsistent. Above you said that "theories" don't have to stem from postulates, they can be "empirical" in nature. Presumably you can recognize the value in pursuing ideas like string theory and MOND. So now your argument hangs on the contradiction that it can be valuable to work beyond what you can trace back to a set of clear postulates when thinking about strings or gravity, but if you do it around decoherence, you are guilty of doing non-serious funambulism. That is precisely the stance I objected to in the very start, you have added nothing to that position beyond simply repeating it. Can you actually argue it with evidence? Quoting Penrose won't work, because as I showed you above, Penrose quotes refute other claims you have made already.

Enough references were given.

Huh? You can prove an argument by referencing a select group of opinions and ignoring the references to the opposite opinion? News flash: the validity of MWI is a hotly debated issue, as this very thread shows. "References" to one side of the story prove nothing, all that is of value is constructing an actual argument with insights that move the discussion forward.

 

[juanrga]

What technical remarks? I saw none, only claims that they exist. In the absence of any actual technical issues around flaws in the descriptions of decoherence, the discussion is already at a more conceptual level.

This proves my point that you ignore the technical arguments...

I recall citing a preprint called «Why decoherence has not solved...». I recall citing a paper explaining why MWI is pure nonsense. I recall citing an online FAQ from a mathematician explaining why «MWI is a smokescreen without a consistent mathematics behind.»

I remember myself citing a paper from Brussels group showing how the evolutor $\Lambda$, explaining decoherence effect among others, is not reducible to U. The paper also shows how up to second order in the coupling and Markovian regime the real evolutor looks as U, although is not U, which is at the origin of the decoherence myth that starting from U one can obtain decoherence from tracing (one can only if one uses «mathematical funambulism», but using funambulism one can prove anything).

And so on and so on.

Many theoretical physicists that I have been exposed to are proponents of MWI, so I can hardly intepret that as evidence that it is not compatible with QM. I guess your reasoning there must be too "technical" for them to understand. But you might find that neither Stephen Hawking nor Roger Penrose agree with your technical objections: in the Wiki on MWI, Hawking's opinion is quoted as saying that MWI is trivially a possible interpretation of QM, but he doesn't think interpretations can really tell us reality (which is my own view as well), and Penrose is purported to agree with Hawking that QM applied to the universe implies MW, but the Wiki says that "Penrose considers the current lack of a successful theory of quantum gravity negates the claimed universality of conventional QM." In other words, MW is QM, but the "technical" problem with both is the same problem. I'm afraid that all makes more sense to me than any of the arguments you've presented so far, but perhaps you haven't made your strongest case yet.

MWI continues being a minority view and claims about its popularity are done by citing some unscientific polls or by saying Hawking-supports-it. Well, Hawking has been supporting all kind of bizarre ideas for decades and shown wrong very often. Recall his recent lost of the bet about QM and information, for instance. For decades, he believed that starting from a unitary evolution, more some horizon, and some hocus pocus information was lost, but evidently information cannot be lost via unitary evolution (by virtue of a well-known theorem). After several decades trying to teach him this, finally he accepts now that he was plain wrong. Hawking has never understood QM, sorry.

Regarding the Wiki, I find interesting that you avoid FAQs, papers, books and preprints, whereas use a Wiki as main support for your claims.

That Wiki affirms that «Penrose agrees with Hawking that QM applied to the universe implies MW» and gives reference 64, but in this 'reference' (an interview of 1991) Penrose says something different. He is not supporting MWI. He says that superposition (a part of QM) on a cat or person would give a many-world view. And in the same reply, it is emphasizing that this particular view about QM is wrong.

Penrose is well-known for his criticism of MWI. In his recent works and his latest books, he affirms that guys as Hawking are not really serious about QM. Penrose correctly states the existence of two irreducible evolutions in QM: U and R. And he correctly notices that people who do not understand this and pretends that only U matters (e.g. Hawking) are not really serious. Sorry, Hawking has never understood QM.

You pretension of that Penrose supports the nonsense of MWI, is in contrast with what Penrose says

[the 'many-worlds' view] is not a very economical description of the Universe but I think things are rather worse than that for the many-worlds description. It is not just its lack of economy that worries me. The main problem is that it does not really solve the problem.

https://www.amazon.com/dp/0521785723/?tag=pfamazon01-20

Effectively, MWI does not agree with observations. I added in this thread that MWI is also internally inconsistent.

No, the point is that the more fundamental theories make different predictions that work. That is all that physicists are interested in

It depends. If your interest is in developing a theory beyond its scope of application, then yes, with the new theory giving new predictions.

If your interest is in correcting inconsistencies of a theory, then new predictions are not in the menu. Example Wheeler and Feynman electrodynamics. Their goal was to correct deficiencies of Maxwell-Lorentz, not to make new predictions.

Yes, many posters have made that claim, and failed to justify it as completely as you have. I prefer to believe Hawking and Penrose than those posters. For my own part, the valid objections I see to MWI are primarily philosophical, and appear when people lose sight of the differences between theories, interpretations of theories, and claims about reality. That is the valid landscape for discussing the various interpretations, not vague allusions to problems that are apparently "too technical" to even discuss!

The claim was proven but you have systematically ignore the proofs. Penrose is also known for not supporting MWI. In his own book he renders himself along with the people who has discredited MWI. Penrose puts himself very far from the Hawking/Everett minority camp (https://www.amazon.com/dp/0521785723/?tag=pfamazon01-20).

https://p.twimg.com/AituXViCQAAfhom.png

Then it is not actually a theory at all, in the literal sense. Your argument here is apparently that theories don't need to be defined by their postulates if someone hangs the label "theory" in the phrase "string theory"! No, "string theory" is just a term, it doesn't mean anything. Theories are still defined by their postulates.

No, a theory of physics does not need to be axiomatized. This is specially true for theories under development, for which would be ridiculous to search axioms when tomorrow the theory can change radically.

And what defines an "empirical theory"? Empirical postulates! You can't have a theory without postulates, they just might not be mathematically closed, in the sense that everything you do with the theory stems directly from the postulates. I already mentioned that this is generally true of physics-- it is quite generally not mathematically closed, it is wide open, and physicists do all kinds of things starting from the basic theories, some that don't pan out at all, others that are effective at understanding some phenomenon in a way that does not follow strictly from any set of postulates of some theory, but rather require additional assumptions that are not laws.

An empirical theory is the collection of empirical laws together with their methods. No paper or book about MOND that I know use the term «postulates», still less «empirical postulates». If you have invented your own terminology, this is fine for you... but I have never used such.

Your argument has become internally inconsistent. Above you said that "theories" don't have to stem from postulates, they can be "empirical" in nature. Presumably you can recognize the value in pursuing ideas like string theory and MOND. So now your argument hangs on the contradiction that it can be valuable to work beyond what you can trace back to a set of clear postulates when thinking about strings or gravity, but if you do it around decoherence, you are guilty of doing non-serious funambulism. That is precisely the stance I objected to in the very start, you have added nothing to that position beyond simply repeating it. Can you actually argue it with evidence? Quoting Penrose won't work, because as I showed you above, Penrose quotes refute other claims you have made already.

Effectively, theories can be empirical. Apart from the examples given before, thermodynamics and electrodynamics both born as empirical theories, before their axiomatization was done.

The contradiction that you allude is only in your mind. I have not objected to empirical descriptions of the decoherence effect. What I have said, and proved with references, is that the so-called decoherence theory by Zurek et al. is based in what van Kampen calls mathematical funambulism. Mathematical funambulism has nothing to see with postulates, but with the fact that decoherence is irreducible to U. Penrose knows this very well. That is why he critizes decoherence guys as Zurek. See figure above again.

 

[Ken G]

Let me briefly summarize what I disagree with from your last post:

1) You seem to think I said Penrose was a proponent of MWI. Obviously, I did no such thing, Penrose is well known to not be an advocate of MWI, nor did I say anything else. What I did say is that Penrose views MWI to be consistent with the postulates of quantum theory "if taken seriously" (his words). The reason Penrose objects to MWI is that it does not connect the theory with what we observe, a problem that he does not think the current postulates of QM resolve at all-- he clearly thinks that new postulates are needed to do that, and he thinks that the new postulates will also include quantum gravity. We are not talking about whether MWI is good physics, or if it will survive a theory of quantum gravity, we are simply discussing whether MWI is a valid interpretation of the existing postulates of quantum theory. You have produced zero evidence that Penrose thinks MWI is not consistent with that, and indeed I have cited evidece that he does, he merely thinks that the current postulates are in a state of flux and require improvement. I also cited evidence that Hawking thinks the postulates are consistent with QM, and he doesn't think Penrose disagrees with that, but he is less bothered by the flaws in the current postulates because his own brand of realism is less demanding on the theories-- they merely need to work in practice. Apparently your arguments rests on the claim that you understand the existing postulates of quantum theory better than both Hawking and Penrose, and I don't see evidence of that either.

2) You argue that the existing postulates of QM require that U and R be mutually irreducible, refuting MWI, and you claim that Penrose makes this argument. However, Penrose does not argue that MWI is logically inconsistent with the postulates of current quantum theory-- that is only an argument that you make. Penrose's argument is much more philosophical-- he simply doesn't think MWI accomplishes the goal that a physics theory should have, and indeed he doesn't think quantum theory yet does that either! That's why he is looking for a new theory. If he actually agreed with you, that MWI is logically inconsistent with the current postulats of quantum theory, he would not need to mention quantum gravity in his objections to MWI. But he does. The natural conclusion is that you are misinterpreting Penrose when you think that he agrees with you that MWI is not consistent with the current postulates of quantum mechanics, instead Penrose thinks MWI won't be consistent with the improved theory he is working toward. Only time can tell on that score.

3) You have cited papers that are relevant to your conclusions, but you do not make the argument for your conclusion. Citing conclusions from papers only demonstrates one thing: you agree with some of the experts . However, citing different conclusions from different papers, or the opinions of Hawking and Penrose as I have done, demonstrates another thing: you don't agree with some of the other experts. This is hardly surprising-- we should certainly know by now that experts disagree on the validity of MWI, and even on why it should be considered valid or invalid. So citing a few experts tells us nothing of interest-- what would be interesting is actually making a case that brings some new insight to the question. All you do is claim that anyone who doesn't agree with you (like Hawking) "doesn't understand quantum mechanics." That is quite a convenient stance-- argument by dismissal.

4) You have said that decoherence theory isn't serious on the grounds that it cannot yet be rigorously traced to the fundamental postulates of any existing theory (the only possible meaning of "funambulism"). In the same breath, you have said that other endeavors, like MOND and string theory, which also cannot be traced to fundamental postulates of any existing theory, are much more serious. Thus, what you consider to be "serious" has no objective criterion, like traceability to fundamental postulates, it is simply that what you personally like is serious and what you don't like isn't serious. I have said that any mathematically closed theory is defined by its postulates, but that is only the rather small subset of physics called mathematical physics-- most of the rest of physics is both quite serious, and also funambulism. So the selective association you choose to make between funambulism and non-seriousness is completely arbitrary, and you have not given it any logical basis, it still boils down to nothing but argument by dismissal.

 

[juanrga]

Let me briefly summarize what I disagree with from your last post:

1) You seem to think I said Penrose was a proponent of MWI. Obviously, I did no such thing, Penrose is well known to not be an advocate of MWI, nor did I say anything else. What I did say is that Penrose views MWI to be consistent with the postulates of quantum theory "if taken seriously" (his words). The reason Penrose objects to MWI is that it does not connect the theory with what we observe, a problem that he does not think the current postulates of QM resolve at all-- he clearly thinks that new postulates are needed to do that, and he thinks that the new postulates will also include quantum gravity. We are not talking about whether MWI is good physics, or if it will survive a theory of quantum gravity, we are simply discussing whether MWI is a valid interpretation of the existing postulates of quantum theory. You have produced zero evidence that Penrose thinks MWI is not consistent with that, and indeed I have cited evidece that he does, he merely thinks that the current postulates are in a state of flux and require improvement. I also cited evidence that Hawking thinks the postulates are consistent with QM, and he doesn't think Penrose disagrees with that, but he is less bothered by the flaws in the current postulates because his own brand of realism is less demanding on the theories-- they merely need to work in practice. Apparently your arguments rests on the claim that you understand the existing postulates of quantum theory better than both Hawking and Penrose, and I don't see evidence of that either.

Penrose does not claim that MWI is consistent with the postulates of quantum theory, you did.

Penrose emphasizes the existence of two evolutions (U & R) in QM, how U and R are mutually irreducible, and how MWI ignores R.

What Penrose is trying to do with his quantum gravity approach is to obtain a dynamical description of R. Other people in the same camp is trying to do the same, but without appealing to exotic quantum gravity effects.

Penrose agrees that MWI is a failed theory, that it does not solves what was supposed to solve, and that is promoted by people who is not really serious about QM. He makes some funny remarks about Zurek. Those remarks are related to the discontinuous arrow that he draws in this figure

https://p.twimg.com/AituXViCQAAfhom.png

If you did not read the book, I will explain you. Penrose notices how Zurek starts from an initial position, claiming that decoherence solves measurement in QM, and that everything what one needs is U. But when Penrose asks to Zurek about the technical details (for example how you reproduce the R of QM using a theory only with U as MWI), for checking if Zurek's claims are to be trusted or not, then Zurek, lacking any serious mathematical/physical response, moves himself towards the MWI camp and avoids to answer the questions. This is another important remark by Penrose: Zurek avoids to answer the technical questions asked to him.

2) You argue that the existing postulates of QM require that U and R be mutually irreducible, refuting MWI, and you claim that Penrose makes this argument. However, Penrose does not argue that MWI is logically inconsistent with the postulates of current quantum theory-- that is only an argument that you make. Penrose's argument is much more philosophical

Here again you pretend to deviate the discussion from the technical level, where MWI has been proven wrong, to some kind of philosophical level, where MWI can be discussed up to exhaust.

The arguments done by Penrose against MWI are technical and of a relatively high mathematical level. Concretely, he uses GR arguments about localization of energy to try to break superposition at space-time level in some kind of speculative quantum gravity scenario.

Penrose gives an equation for estimation of the breaking of a spacetime superposition. His formula predicts that cats and larger objects never follow Sch evolution. The universe as a whole does not follow the Sch law, which goes against one of main MWI assumptions.

Philosophical arguments are only in the MWI camp.

3) You have cited papers that are relevant to your conclusions, but you do not make the argument for your conclusion. Citing conclusions from papers only demonstrates one thing: you agree with some of the experts . However, citing different conclusions from different papers, or the opinions of Hawking and Penrose as I have done, demonstrates another thing: you don't agree with some of the other experts. This is hardly surprising-- we should certainly know by now that experts disagree on the validity of MWI, and even on why it should be considered valid or invalid. So citing a few experts tells us nothing of interest-- what would be interesting is actually making a case that brings some new insight to the question. All you do is claim that anyone who doesn't agree with you (like Hawking) "doesn't understand quantum mechanics." That is quite a convenient stance-- argument by dismissal.

I would agree, except because Penrose agrees with me and because Hawking is not an expert. In the above figure Penrose puts Hawking very far from known experts in QM (what he calls people really serious about QM). The contributions of Hawking to the topic of QM are easily summarized: zero. Therefore, this is understandable.

Indeed, most what Hawking has said about QM and QG has been shown wrong. I illustrated the example of information paradox in QM, which Hawking lost, because is very relevant to the failure of MWI.

I explained to you that Hawking mistake regarding the information paradox was due to Hawking unability to understand unitarity and theorems derived from it (as conservation of information).

In essence, Hawking pretended that information was lost via an evolution law conserving information. This evidently is nonsense. He tried to support his opinion via mathematical funambulism. Many of us said that Hawking was wrong, but he did need several decades to understand this topic. It is fair to say that he nows acknowledge that he was wrong about unitarity and he now claims that information is not lost.

Hawking makes essentially the same mistake regarding quantum measurements. Well-known mathematical results prove that starting from U, one cannot obtain R. Myself cited a paper where some of those theorems are given.

The fathers of QM knew this and added the collapse postulate to the Sch law. Penrose knows this and accepts both R and U. The serious people in the above figure know all this as well. Only Hawking and some other few cosmologists ignore this.

4) You have said that decoherence theory isn't serious on the grounds that it cannot yet be rigorously traced to the fundamental postulates of any existing theory (the only possible meaning of "funambulism"). In the same breath, you have said that other endeavors, like MOND and string theory, which also cannot be traced to fundamental postulates of any existing theory, are much more serious. Thus, what you consider to be "serious" has no objective criterion, like traceability to fundamental postulates, it is simply that what you personally like is serious and what you don't like isn't serious. I have said that any mathematically closed theory is defined by its postulates, but that is only the rather small subset of physics called mathematical physics-- most of the rest of physics is both quite serious, and also funambulism. So the selective association you choose to make between funambulism and non-seriousness is completely arbitrary, and you have not given it any logical basis, it still boils down to nothing but argument by dismissal.

I have not said that «decoherence theory isn't serious on the grounds that it cannot yet be rigorously traced to the fundamental postulates of any existing theory». And I do not want to discuss about your systematic reinterpretation of my words.

 

[Ken G]

What Penrose is trying to do with his quantum gravity approach is to obtain a dynamical description of R. Other people in the same camp is trying to do the same, but without appealing to exotic quantum gravity effects.

Yes that's just what I said-- all those people think the current postulates of quantum mechanics require improvement, because they do not provide a dynamical description of R. This clearly demonstrates that the current postulates of QM don't provide that, or there would be no need for this effort. And you are arguing that MWI is inconsistent with those current postulates because it also doesn't provide that, so your argument that MWI is inconsistent with QM does not logically follow.

What I hear Penrose and Hawking as saying are the following. Penrose is saying the current postulates of QM are unsatisfactory because they lack an overarching description of how to connect the predictions of the theory with what we actually experience-- that connection is currently done in various ad hoc ways, which each interpretation gives its own accounting of. Hawking is agreeing with that, but doesn't see it as so much of a problem, so long as the predictions can be obtained by hook or by crook.

Note that none of this implies that MWI is inconsistent with the existing quantum theory, even though both lack a rigorous way to connect predictions and observations that stem directly from some set of postulates, absent any "funambulism." I suspect that both Penrose and Hawking would take a similar stance about any of the other interpretations of QM-- none of them would be satisfactory to Penrose because QM isn't satisfactory, and all are basically OK by Hawking because they all make the same predictions at the end of the day.

Penrose agrees that MWI is a failed theory, that it does not solves that was supposed to solve, and that is promoted by people who is not really serious about QM (that is an elegant way to say people-who-do-not-understand-QM).

That is all entirely consistent with everything I said about Penrose's position. In particular, at no point does it imply that MWI is not a valid interpretation of the current quantum theory, and at no point does it imply that decoherence theory is not a valid effort to understand why the current quantum postulates are as effective as they are. It is also completely consistent with the pervasive fact that Penrose's objections all trace back to his fundamental discontent with current quantum theory, as I said. Once it is clear that Penrose is "serious" about fixing quantum mechanics, it is obvious that he will view as "non-serious" any attempts to "patch" those flaws with informal (or "empirical") efforts to understand why QM is effective despite its blemishes. What that all reflects is Penrose's personal views about what direction mathematical physics should be taking in its usual efforts to underpin already existing theories with greater mathematical rigor, and his hopes that in the process, quantum gravity can be achieved.

Here again you pretend to deviate the discussion from the technical level, where MWI has been proven wrong, to some kind of philosophical level, where MWI can be discussed up to exhaust (but without changing a bit the technical conclusions).

No interpretation of QM has been "proven wrong"-- as I said, the issue with proving anything about any theory is that physics is not closed, and so there simply is no postulational basis that anyone can use to "prove" anything about QM without making additional assumptions, usually quite philosophical in nature (as in Penrose's idea that a theory must be able to connect its predictions to what we perceive, directly from the postulates of the theory-- absent funambulism, even though actual physics doesn't do that in practice). This is the fact you keep ignoring-- your entire argument is that anyone (like Hawking, or Zurek, or Gell-Mann, or many of the other names in that figure) who does not share the philosophical priorities that make "technical" proofs possible in the first place, must not understand quantum mechanics. The real problem is, you do not understand the role of philosophy, you are just another one of those who think that philosophy is about other people's opinions, but your own philosophy is buried in "technical" issues.

The arguments done by Penrose are evidently technical and of a relatively high mathematical level. Concretely, he uses GR arguments about localization of energy to try to break superposition at space-time level in some kind of speculative quantum gravity scenario.

And this proves my point completely. You just mentioned GR in a "technical" proof about the postulates of current quantum theory! Once again: Penrose is not making proofs about quantum mechanics, he is making proofs under assumptions about how quantum gravity might work. He is imposing his view of what the next theory needs to do, and is making proofs about how it would have to do it. That's a very valuable thing to do, especially if Penrose's mission turns out to be possible, but it certainly isn't what you are misquoting it to be.

You claim that his arguments are «philosophical», but this is plain wrong, of course. Penrose gives an equation for estimation of the breaking of a spacetime superposition. His formula predicts that cats and larger objects never follow Sch evolution. The universe as a whole does not follow the Sch law, which goes against one of main MWI assumptions.

So now you are claiming that Penrose can prove how the universe must work without making any philosophical assumptions about how the universe works? That's just what I mean about the logical holes in your stance. No, what Penrose is quite clearly doing is applying philosophical beliefs to find the direction of the next theory, just as Einstein did in originally deriving GR.

I explained to you that Hawking mistake regarding the information paradox was due to Hawking unability to understand unitarity and theorems derived from it (as conservation of information).

And I explained to you that no one knows the answer to that bet, because there is no theory of quantum gravity. All that happened was Hawking was convinced to change his mind about how the next theory might work. You pretend that the answer is already known, just as you pretend that Penrose can prove how reality will work based on "estimations of the breaking of spacetime superpositions." Sorry, this is all philosophy until there is demonstrable evidence of the success of a new theory, regardless of how "technical" the philosophical arguments can become. One would think you don't even realize that mathematics is used in philosophy too!

Hawking makes the same mistake regarding quantum measurements. Well-known mathematical results prove that starting from U, one cannot obtain R. He pretends that one can but he is plain wrong. I have given the arguments before, I haver given the papers before, I have given the mathematical FAQ before...

No need to repeat, true?

True, I don't expect you to rehash things you have already put a lot of work into establishing, and it is certainly clear you have spent a lot of time on the issue and have achieved a high degree of technical mastery. All the same, it is not at all uncommon for people with high levels of technical mastery to have lost sight of the basic philosophical assumptions they have made along the way, and those assumptions show up in the proofs (for example, that U cannot obtain R. On what closed system? Is the observer in there? Is the way the observer perceives and thinks in there? Is the way the observer tested the postulates of the theory in there?)

I know that some people believes that Earth is flat. No paper, book, website, theorem, argument, photograph, experiment, or anything makes they change their opinion. I am well aware that this also happen with some MWI people who never will accept that MWI is nonsense.

I am not an "MWI person", so I don't have to feel personally insulted by this remark, but all the same I have pointed out the flaws in your argument that make it impossible for you to call this a logical conclusion. It's actually just your opinion-- the simple truth is, no one has the slightest idea whether MWI will be consistent with the postulates of the next theory, whether it unifies QM and GR or QM and the way the mind does physics. But I can certainly agree that based on nothing other than simply being consistent with the current quantum theory, that is no justification to use MWI to make claims about reality.

 

[juanrga]

Yes that's just what I said-- all those people think the current postulates of quantum mechanics require improvement, because they do not provide a dynamical description of R. This clearly demonstrates that the current postulates of QM don't provide that, or there would be no need for this effort. And you are arguing that MWI is inconsistent with those current postulates because it also doesn't provide that, so your argument that MWI is inconsistent with QM does not logically follow.

Contrary to your misconception, there is not need to demonstrate limits of the current postulates of QM today, because the limitations of the postulates are well-known since that QM born. Everyone who has studied QM knows that the projection postulate is not a dynamical postulate. In fact, there is not even variable time in that postulate.

The extension or improvement of QM was not the point. The point I was making was about your incorrect claim that Penrose supports/likes/accepts MWI, when he does not clearly.

I am not «arguing that MWI is inconsistent with those current postulates because it also doesn't provide» a dynamical description of R. What I said is totally different. I said that MWI is both internally inconsistent and incompatible with QM by other reasons. I said, for instance, that MWI cannot give R, because R is irreducible to U.

I think this is rather easy to understand. If you start with a theory like MWI that uses only U, you cannot obtain R.

If you look to the figure above you can see that really serious people (i.e., people who understand QM) uses both R and U. People who do not understand QM (fortunately a tiny minority), believes that MWI is another interpretation of QM, but, as has been shown in this thread, MWI is a misinterpretation of QM.

Your following misconceptions and rewrites of Penrose were already corrected before.

The rest of your post is a new collection of misconceptions and systematic rewrites of what I and others said. I will be brief,

Nowhere I said that Gell-Mann does not understand QM. You said it.

Nowhere I said that GR is needed to prove the postulates of QM. You said it.

Nowhere I said that Penrose can prove how reality will work based on estimations of the breaking of spacetime superpositions. You said it.

And so on.

In fact, apart from not saying anything of that, I have said the contrary, which makes still more funny your tactic. For instance, regarding Penrose's work in spacetime superpositions I wrote:

What Penrose is trying to do with his quantum gravity approach is to obtain a dynamical description of R. Other people in the same camp is trying to do the same, but without appealing to exotic quantum gravity effects.

Which is a way to say that those exotic effects are not needed for understanding R.

There are many more misconceptions and very serious mistakes in the rest of your post...

 

[Ken G]

Contrary to your misconception, there is not need to demonstrate limits of the current postulates of QM today, because the limitations of the postulates are well-known since that QM born.

Tell me, just where do you imagine that I said there is a need to "demonstrate" the limits of the postulates today? Nowhere. What I actually said is that some people are working to fix these limitations, hoping to create a new set of postulates that are not necessarily the ones that MWI is consistent with (my whole point here), such as Penrose, while others, such as Hawking, are not bothered by the limits of those postulates because the experiments can be predicted either way. That is just what Hawking meant when he said that Penrose is a Platonist (someone who would be bothered by limits in the postulates because he believes the postulates are trying to be the reality) whereas he is a positivist (someone who believes that all we can ever say about reality is the outcome of our experiments, so if we predict those, that's the best we can ever hope to do.) You are not hearing what I'm saying, you seem to need to keep replacing it with something else so you can refute what I never said.

Everyone who has studied QM knows that the projection postulate is not a dynamical postulate. In fact, there is not even variable time in that postulate.

Yes of course, anyone who has studied the current postulates of QM, like you, like me, like Hawking, etc., does indeed know that, because it is perfectly obvious. It also has nothing to do with anything I've said in this whole thread. The question is, why do you think it does? Because you're not hearing anything I'm saying?

The extension of QM was not the point. The point was your incorrect claim that Penrose supports/likes/accepts MWI, when he does not.

Please quote me where you imagine I said that Penrose likes or accepts MWI! I never said (or thought) any such thing, and indeed I clarified several times that I never said that. One more time: what I said, and continue to maintain, is that the reason Penrose rejects MWI is the same as the reason he feels the postulates of QM are unsatisfactory, to wit, the theory is not directly connected to what we perceive without ad hoc nondynamical treatments of wave function collapse. What's more, the sole thing that distinguishes the various interpretations of QM is how they handle the ad hoc character of this collapse that is in the current postulates of QM. This is also why they are all perfectly consistent with QM, they simply do what is ad hoc (their funambulisms) in different ways. Someone like Hawking, who only cares that it works, isn't too bothered by that; someone like Penrose, who wants the postulates to be a description of the reality itself, is bothered by that. What this all means is that Penrose would object to all the interpretations of QM, because he objects to QM itself-- until its postulates can be "fixed", and hopefully include gravity.

I have not said that the problem with MWI is a lack of dynamical description of R. What I said is that MWI cannot give R, because R is irreducible to U.

And I have said that this theorem requires essentially philosophical assumptions that any MWI enthusiast would reject. That's what I meant when I said you are simply overlooking your own philosophical biases. I asked you where in the proof of the theorem you quote is there an observer, where is there an observer's mind, and where is there the epistemology that observer chooses to use to decide what it means for a theory to be valid. Until you put those things in your proof, you have not gone beyond your own philosophical assumptions. So we return to my original remark: physics is not mathematics. We can now append this remark: mathematical physics is impossible to connect with the rest of the body of physics without philosphical assumptions, and much of the debate that has people like Penrose saying Deutsch is "not serious" while Deutsch says Penrose is doing "aesthetics not physics", is all around their different philosophical assumptions and objectives for physics.

I think this is rather easy to understand. If you start with a theory that uses only U, you cannot obtain R.

If this were as categorically true as you imagine, then no one would have thought MWI is a reasonable interpretation of QM. So you now have an argument on the table that says "it is easy to understand that MWI could never be an interpretation of QM." Can you see the logical flaw in your position? I can. It holds that any proponent of MWI is an idiot. I think you actually believe that, but your logic is faulty because you have not tracked your own assumptions.

The actual truth is that if you start with only U, you cannot obtain R without altering your philosophical preconceptions about what physics should be trying to do, or how we should regard the connection between physics and reality, especially in regard to the importance of empiricism. It you want it 'more "technically", just look at the proof of any theorem that says you can't get R from U, and look where the philosophical assumptions come in. You might need to see outside your box a bit more.

If you look to the figure above you can see that really serious people (i.e., people who understand QM) uses both R and U. ...

Um, I think you should have a look at your own figure again. Penrose puts the "only U" camp under "serious about psi". Perhaps your own definition of "serious" is a little different from Penrose's? As near as I can tell, you define it as "agrees with me". (But you are right that I misplaced Gell-Mann.)

Nowhere I said that GR is needed to prove the postulates of QM. You said it.

I did? News to me. How does one "prove a postulate"? I might imagine proving the consistency of two different postulates, but of course no one thinks the postulates of GR are consistent with the current postulates of QM.

For instance, regarding Penrose's work in spacetime superpositions I wrote...
Which is a way to say that those exotic effects are not needed for understanding R.

Yet Penrose thinks those exotic effects are needed for understanding R. So like I said, the experts do not agree at the frontier-- so simply citing their opinions does not prove anything. But even more to the point, Penrose does not think that the current postulates of QM allow us to understand R! That is all I need to establish my argument-- if Penrose really thought that MWI is not consistent with the current postulates of QM (and there is no evidence he does, and evidence to the contrary like what Hawking said about Penrose's position), then whey would he bother to criticize MWI on the grounds that you can't use it to get R from U dynamically without going to new postulates? The answer is, all he cares about is the latter issue, it is of no concern to him if MWI is consistent with the current postulates, and indeed I believe he thinks it is.

There are many more misconceptions and very serious mistakes in the rest of your post...

Correction, there are many more mistakes in your furtive imagination applied to my posts. You first must demonstrate that you can actually hear the words I am using before you can critique them effectively. Communication is the hardest thing.

What Penrose thinks is that the current postulates of QM need modifying, in ways that, once they accomplish what Penrose's philosophical preferences convinces him they should, will leave no room for MWI. That is not a claim that MWI is inconsistent with the current postulates of QM, and it not a claim that Penrose's program will work. I can't say it any clearer than that.

 

[juanrga]

That is just what Hawking meant when he said that Penrose is a Platonist (someone who would be bothered by limits in the postulates because he believes the postulates are trying to be the reality) whereas he is a positivist (someone who believes that all we can ever say about reality is the outcome of our experiments, so if we predict those, that's the best we can ever hope to do.)

And Penrose correctly points that the central issue «has very little to see with Platonism/positivism». Moreover, Penrose does not consider himself a Platonist...

What's more, the sole thing that distinguishes the various interpretations of QM is how they handle the ad hoc character of this collapse that is in the current postulates of QM. This is also why they are all perfectly consistent with QM, they simply do what is ad hoc (their funambulisms) in different ways.

This is all untrue. You also continue using the term «funambulisms» in a different way to how I introduced the term here.

Someone like Hawking, who only cares that it works, isn't too bothered by that; someone like Penrose, who wants the postulates to be a description of the reality itself, is bothered by that.

Hawking believes that MWI works, but he, of course, has never proved such thing. However, the contrary thing, --i.e., that that MWI does not work-- has been proven.

Penrose is bothered because MWI does not work (bold face from mine):

[MWI] is not a very economical description of the Universe but I think things are rather worse than that for the many-worlds description. It is not just its lack of economy that worries me. The main problem is that it does not really solve the problem.

I asked you where in the proof of the theorem you quote is there an observer, where is there an observer's mind, and where is there the epistemology that observer chooses to use to decide what it means for a theory to be valid. Until you put those things in your proof, you have not gone beyond your own philosophical assumptions.

I wonder why you think that the mathematical proof that R and U are irreducible needs of such inputs as an «observer mind». I know that most of philosophical literature is rather confused about QM and still believe that collapse of wavefunctions is caused by the mind of an observer, but this all is the usual philosophical nonsense that lead to the well-known physicists reply: «Shut up and Calculate».

If this were as categorically true as you imagine, then no one would have thought MWI is a reasonable interpretation of QM.

There are many instances of correct statements that, however, are denied by some minority of persons with philosophical prejudices.

For instance, «Earth is not flat» is a correct statement. Still some people today think that their Flat Earth 'theory' is a reasonable interpretation of the properties of our planet, and they even join in a Society

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

My point here is that it does not matter how many times MWI is proven wrong, useless or nonsensical; you probably will always find someone who supports MWI.

The actual truth is that if you start with only U, you cannot obtain R without altering your philosophical preconceptions about what physics should be trying to do, or how we should regard the connection between physics and reality, especially in regard to the importance of empiricism. It you want it 'more "technically", just look at the proof of any theorem that says you can't get R from U, and look where the philosophical assumptions come in. You might need to see outside your box a bit more.

Evidently the mathematical proof that U and R are irreducible has nothing to see with «philosophical preconceptions» neither with «philosophical assumptions».

Um, I think you should have a look at your own figure again. Penrose puts the "only U" camp under "serious about psi". Perhaps your own definition of "serious" is a little different from Penrose's? As near as I can tell, you define it as "agrees with me". (But you are right that I misplaced Gell-Mann.)

Not only I am right on that you misplaced Gell-Mann, but you continue misreading and confusing everything.

If you were to read what I wrote, then you would see that I wrote «really serious». Although you think that is my definition, it is not mine. Penrose explains, in his book, who in that diagram is really serious (Penrose own words) about QM and who is not.

For instance, Penrose correctly claims that Hawking is not «really serious» about QM.

It seems evident that you confound «serious about psi» with my «serious about QM». The «serious about psi» label is different. Penrose uses this label to differentiate those who believe that Psi is something about our mind of those who understand that Psi gives the physical state of the quantum system.

 

[Ken G]

Hawking believes that MWI works, but he, of course, has never proved such thing. However, the contrary thing, --i.e., that that MWI does not work-- has been proven.

Penrose is bothered because MWI does not work (bold face from mine):

Often you have claimed that MWI is inconsistent with the current postulates of QM, and you've claimed this has been proven (I already told you that any such proofs will express philosophical priorities that need not be accepted), and now you actually bold-face a sentence by Penrose as if it supported this stance, yet it clearly says nothing of the sort! That's your evidence? What Penrose said is that MWI doesn't solve the problem with QM. That is just precisely what I told you that Penrose felt about MWI. Yet you see no importance in what Penrose did not say: that MWI is inconsistent with the current postulates of QM! You are an intelligent person, probably extremely so, so why can you not see that if Penrose thought MWI was inconsistent with the postulates of QM he would have said so?

I think it is pretty clear what Penrose is actually saying-- he is saying that MWI doesn't solve the problems that the the current postulates of QM have. That means, he doesn't think MWI goes beyond those postulates, in the way his own intepretation attempts to do.

I wonder why you think that the mathematical proof that R and U are irreducible needs of such inputs as an «observer mind».

Simple. The proof will make assumptions about what it is talking about. Anyone who simply rejects those assumptions, say on the grounds that it does not make any account of the observer's mind (which is obviously part of any complete accounting of physical phenomenon), and thus reject the "proof." That is the nature of proofs: they are only as good as their assumptions.

I know that most of philosophical literature is rather confused about QM and still believe that collapse of wavefunctions is caused by the mind of an observer, but this all is the usual philosophical nonsense that lead to the well-known physicists reply: «Shut up and Calculate».

Apparently you are unaware that "shut up and calculate" is also a philosophical stance. Most people do realize that. More to the point, shutting up and calculating means use QM to make predictions, which we already know how to do and nothing that Penrose is doing has anything to do with that (he hopes his approach can be empirically demonstrated, but that is certainly not why he is doing it, and frankly there is fairly little likelihood that it will be empirically demonstrated any time soon).

My point here is that it does not matter how many times MWI is proven wrong, useless or nonsensical; you probably will always find someone who supports MWI.

Well, you might think that comparing Hawking and DeWitt to Flat Earth society members is a cool rhetorical device, but I think it is meaningless hooey.

Evidently the mathematical proof that U and R are irreducible has nothing to see with «philosophical preconceptions» neither with «philosophical assumptions».

That is where you are quite wrong, as I explained above. Maybe we would make better progress if you would cite such a proof, and then I will show you the philosophical assumptions involved.

It seems evident that you confound «serious about psi» with my «serious about QM». The «serious about psi» label is different. Penrose uses this label to differentiate those who believe that Psi is something about our mind of those who understand that Psi gives the physical state of the quantum system.

See? Your philosophical preferences are showing already, yet you seem blind to them. Your position is evidently that it is an objective fact that Psi gives "the physical state of a quantum system." What is a physical state? What is a quantum system? Please prove to me what these things are. Use pure mathematics please, no "funambulism". Oh, and no philosophy either, obviously.

 

[juanrga]

Often you have claimed that MWI is inconsistent with the current postulates of QM, and you've claimed this has been proven (I already told you that any such proofs will express philosophical priorities that need not be accepted), and now you actually bold-face a sentence by Penrose as if it supported this stance, yet it clearly says nothing of the sort! That's your evidence?

I have bold-faced a sentence by Penrose by another reason, evidently.

The proofs that MWI is internally inconsistent and disagree with QM predictions were given many messages ago and repeated often...

Simple. The proof will make assumptions about what it is talking about.

This is untrue.

Anyone who simply rejects those assumptions, say on the grounds that it does not make any account of the observer's mind (which is obviously part of any complete accounting of physical phenomenon), and thus reject the "proof."

Philosophers are very confused about this topic.

It is not needed to appeal to observer's mind to understand quantum measurement, just as it is not needed to appeal to observer's mind to explain how a thermometer works.

The idea that quantum measurement has something to see with a human mind is pure nonsense.

Apparently you are unaware that "shut up and calculate" is also a philosophical stance.

You seems unaware that the slogan was invented to avoid the rambling endlessly about the philosophical implications of QM, and is appropriate to use when there is an imbalance between the amount of philosophy and the amount of calculation.

Maybe we would make better progress if you would cite such a proof, and then I will show you the philosophical assumptions involved.

The mathematical proofs were given to you several times before, and you systematically ignored. Although you continue disputing them using philosophical pseudo-arguments.

See? Your philosophical preferences are showing already, yet you seem blind to them. Your position is evidently that it is an objective fact that Psi gives "the physical state of a quantum system." What is a physical state? What is a quantum system? Please prove to me what these things are. Use pure mathematics please, no "funambulism". Oh, and no philosophy either, obviously.

Once again the «philosophical preferences» are only in your mind.

If you open a textbook in QM (I cited some), you can learn why Psi gives the physical state of a quantum system. Examples of quantum systems and their properties are given as well in textbooks.

Of course, the concept of physical state is more general. For instance, any textbook on thermodynamics will explain you what is the physical state of a thermodynamic system at equilibrium.

Such books are to be found in the Physics section (not in the philosophy section) of your favorite library.

 

[Ken G]

I have bold-faced a sentence by Penrose by another reason, evidently.

And evidently, I'm missing the bold-faced sentence where Penrose actually says what you keep claiming he is saying: that MWI is inconsistent with any theory that can make the same tested predictions as the current postulates of QM that can be found in standard textbooks. Your argument lacks evidential support in a very blatant and obvious way, yet in all your posts, you cannot correct this gaping flaw.

The proofs that MWI is internally inconsistent and disagree with QM predictions were given many messages ago and repeated often...

And I repeated many times that to be what you claim, such proofs must stick entirely to the postulates of QM, with no philosophical assumptions at all. As such, they must use the postulates of QM to present a complete accounting of everything that is involved in a "QM prediction", including how such predictions are confronted with observations (to give the concept of "prediction" meaning in the first place). As such, they must account for the observer involved in verifying the prediction. They don't. Now, you might think that's a technicality, but obviously it isn't, as this is precisely the crux of many of the distinctions in the interpretations of QM. But I'm repeating myself.

This is untrue.

So you claim, but you are wrong. To see this, all we need to do is what I suggested we do: present me with such a "proof", and I will show you where the philosophical assumptions appear, and how an MWI proponent could reject those assumptions. It's really quite simple-- you can't get R from U, but the MWI proponent doesn't think you ever get R. You only get R when you adopt certain philosophical assumptions about what a prediction is, and how physics should work. Go ahead, show me your favorite proof, this won't take long.

Philosophers are very confused about this topic.

When it comes to issues like this, everyone is a philosopher. You are just another one of those who defines "philosophy" as "everything I don't agree with", and "scientific fact" as "everything I do." But that's not actually what philosophy is. I'm sure Penrose understands the role of philosophy, as Hawking clearly does as well. Penrose merely adopts the label "very serious about QM" for people who share his philosophical objectives. Many others, like Mermin, do not-- they don't think QM is anything but a system for making predictions, and there is no dispute among anyone about how to use QM to do that, at least in regard to everything that has already been observed that is used to support QM.

It is not needed to appeal to observer's mind to understand quantum measurement, just as it is not needed to appeal to observer's mind to explain how a thermometer works.

Interesting philosophical opinions. I would say they are quite naive, as is typical of people who don't know when they are using philosophy.

The idea that quantum measurement has something to see with a human mind is pure nonsense.

More philosophical opinionating. But I would say it is perfectly demonstrable that all of physics, not just quantum measurement, as "something to do with the human mind." Indeed, I would say that is quite obvious, but what is obvious to me and what is obvious to you can be very different things, and since we are both intelligent, this must trace back to our different philosophical priorities and assumptions. The main difference between us is that I realize this and you do not.

You seems unaware that the slogan was invented to avoid the rambling endlessly about the philosophical implications of QM, and is appropriate to use when there is an imbalance between the amount of philosophy and the amount of calculation.

I know perfectly well why the slogan was invented. I also know the words of Aristotle: "If you will philosophize, then you will philosophize. If you will not philosophize, then you will philosophize." Or those of Blaise Pascal: "To ridicule philosophy is really to philosophize." Either ponder on those, or dismiss the intelligences of Aristotle and Pascal. The truth is that "shut up and calculate" is not a means for avoiding philosophy, it is a philosophy, it is a very deep statement about the limitations of science that most scientists like yourself given your claim that those who understand QM know that a wave function is truly a "physical state", while dodging the request to even define that term) are loathe to believe, yet think they are "serious" in their disbelief.

The mathematical proofs were given to you several times before, and you systematically ignored. Although you continue disputing them using philosophical pseudo-arguments.

Pick your favorite one, anyone will suffice, and cite the assumptions that it uses. I may have to uncover the implicit ones, though.

Once again the «philosophical preferences» are only in your mind.

I realize you believe this, simply repeating your beliefs is rather pointless. Or is that what you call a logical argument?

If you open a textbook in QM (I cited some), you can learn why Psi gives the physical state of a quantum system. Examples of quantum systems and their properties are given as well in textbooks.

Now your argument is just plain silly. Of course I know all about QM textbooks, as do all the other people who don't think that psi is a "physical state" (they begin by attempting to define the term, which of course is the whole point-- by not even trying to do that, you expose the frailty of your position). The fact is, textbooks are not interested in establishing their philosophical assumptions, they are all implicit. This is simply because textbooks are not trying to probe the philosophical foundations of QM that would let you actually prove the things you claim that QM can prove. Instead, textbooks are interested in laying out the theory well enough that it can be used to make calculations, but it always dodges the issue of collapse. This is the entire reason that we have so many different interpretations of QM in the first place! You appear to think we can sector those interpretations into two camps: those that agree with your implicit philosophical assumptions, which you call the "serious" ones, and those that do not, which you dismiss. That is actually quite typical behavior of people who don't understand philosophy, I see it on all sides of the interpretation debates. That's why I pointed out that Deutsch claims Penrose is "doing aesthetics not physics", while Penrose says Deutsch is "not serious." Obviously, these people cannot agree, and the clear reason is they have not recognized how their philosophical opinions have colored their judgements. What gives Penrose the right to judge what is serious? What gives Deutsch the right to judge what is physics? These are issues that physicists do not agree on, it's just that simple-- deal with it!

Of course, the concept of physical state is more general. For instance, any textbook on thermodynamics will explain you what is the physical state of a thermodynamic system at equilibrium.

And in the process, will make idealizations and philosophical assumptions. The point is, I can very easily recast thermodynamics, or any physics theory, into something that looks completely different, yet makes all the same predictions that can actually be tested, yet proves very different things about what that theory can and cannot do, by simply adopting a very different philosophical stance. This is precisely what you do not realize.

 

[juanrga]

And evidently, I'm missing the bold-faced sentence where Penrose actually says what you keep claiming he is saying: that MWI is inconsistent with any theory that can make the same tested predictions as the current postulates of QM that can be found in standard textbooks. Your argument lacks evidential support in a very blatant and obvious way, yet in all your posts, you cannot correct this gaping flaw.

Therefore your argument has moved from Penrose-agrees-with-me to show me a sentence where Penrose-agrees-with-you.

Sorry, but I do not need to find a sentence from Penrose supporting my claim that MWI is nonsense. I already supported my claim.

Maybe you missed this point again, but the reason which I cited Penrose was because you pretended him to support your philosophy, when he just agrees with me that MWI is both inelegant and not-working. Read the quotes again.

It's really quite simple-- you can't get R from U, but the MWI proponent doesn't think you ever get R. You only get R when you adopt certain philosophical assumptions

This very much summarizes the point.

Effectively, as I repeated and repeated R cannot be derived from U (because is irreducible). That is the reason which QM includes both R and U.

Although for decades the MWI community has done claims that they have an alternative interpretation of QM using only U, their theory is internally inconsistent and disagrees with QM predictions.

Now you finally agree that the R that cannot be obtained from U can be 'obtained' from U when, your own words, «you adopt certain philosophical assumptions»

I am really satisfied and this point.

Thank you.

 

[Ken G]

Therefore your argument has moved from Penrose-agrees-with-me to show me a sentence where Penrose-agrees-with-you.

Actually, I already presented the evidence that Penrose agrees with me-- the problem is that you have presented none that he agrees with you. As this is the crux of your entire position here, I think that is a serious flaw in your stance.

Sorry, but I do not need to find a sentence from Penrose supporting my claim that MWI is nonsense. I already supported my claim.

As I expected, you still cannot provide evidence that the Wiki article was wrong when it claimed that Penrose thinks MWI is consistent with current QM, but that current QM is missing something important, and so by implication MWI is missing something important. I agree with the Wiki, it completely checks with all the evidence presented in this thread, nor have you refuted it with a shred of evidence.

Maybe you missed this point again, but the reason which I cited Penrose was because you pretended him to support your philosophy, when he just agrees with me that MWI is both inelegant and not-working. Read the quotes again.

Yet again you are imagining something that never had anything to do with this thread. It is clear you have no idea what I'm saying every time you attempt to summarize it. You would actually do much better sticking with my words.

This very much summarizes the point.

I know that R, a well-defined physical and mathematical entity, cannot be derived from U (because is irreducible).

That has never been the source of the disagreement. Read my words again. The source of the disagreement is whether or not we can take it as a scientific fact that we do get "R". I have told you that this "fact" actually requires certain philosophical assumptions and priorities that are not required to adopt, and indeed MWI proponents generally do not, which is pretty much the entire point. There is no experiment that requires that R be part of the reality that QM postulates are trying to describe, there is just the observer perception, which as I said is not part of your theory, or any theory, of QM. Until that problem is fixed, if it can be fixed, the issue will always reduce to philosophical priorities-- largely around the role of rationalism and empiricism in asserting what a physics theory is trying to do.

Although for decades the MWI community has done bogus claims that they had derived, all the 'derivations' have been showed to be wrong.

That is also not the least bit relevant to this thread. The issue was not whether MWI could derive R from U according to some set of laws (we should know that is impossible), it was simply whether or not MWI is a consistent interpretation with the fact that we perceive R. That is entirely different-- for example, CI never makes any effort whatsoever to "derive R" from some deeper principles, yet obviously CI is consistent with R because it simply includes it as an ad hoc postulate (something Penrose sees as a big problem, and Hawking does not, both for philosophical reasons). Similarly, MWI includes the ad hoc postulate that R is perceived because of the action of the perceiver, and the fact that it has not succeeded in connecting that to any deeper principles seems to me like a perfectly obvious extension of the problem of having no theory of perceivers. Nor do you, nor does Penrose.

So given the absence of a theory of quantum gravity that can do what Penrose would like it to do, and given the absence of a theory of perceivers that can do what I am saying would be necessary to do, what these "proofs" actually accomplish is simply tracking the logical ramifications of the various philosophical priorities in concert with what has been experimentally established about quantum systems. That is what I have been trying to tell you all along.

As a mathematician working in foundations of QM has said «MWI is a smokescreen without a consistent mathematics behind.»

That is also irrelevant to the thread. Nowhere did I claim that MWI gives a mathematically closed accounting of the predictions of QM, I said it is an interpretation that is consistent with those predictions. The predictions require nothing beyond the mathematics of how to do them, which there is no disagreement about. What there is disagreement about is how to find a set of postulates that put those predictions on a sound and rigorous mathematical footing, which simply does not exist at present (because of the problem of no dynamical accounting of the perception of collapse). That's why Penrose, and others, are trying to create one! Why on Earth would they need to do that if one already existed?

I am really satisfied and this point I have stopped from reading the rest of your post.

Thank you.

Unfortunately you still have understood nothing I said. Pity, your inability to understand these nuances will continue.

 

[fellupahill]

Hello,

While the majority of physicists embrace the Many Worlds interpretation of quantum decoherence, I am holding out hope for the Copenhagen interpretation or better yet, a undiscovered interpretation.

Please allow me to pose three problems I have with the MW interpretation.

1) There is a nonzero prob of me spontaneously becoming a miniature sun. Let me elaborate. Since I am made of atoms, there is a nonzero prob that all of the subatomic particles comprising each of the nuclei of my atoms are all one kilometer away except for a single proton and single electron in each atom. I.e. I am now spontaneously comprised of only hydrogen atoms. Now let's say that since even the exact position of these hydrogen atoms is uncertain they are close enough that gravity overpowers all and nuclear fusion takes place. I.e. I have become a miniature sun.

The probability of this happening is obviously miniscule, but nonzero. With the CI interpretation this will never happen because the probability is so small that the universe is not old enough for such a low probability to have been realized. However with MWi since the probability is nonzero, it has happened. Moreover it has been happening every second of every day since the minute I was born in some parallel universe.

2) My second problem with MW intepretation is how can an interference pattern result in a double slit experiment if the particle is actually traveling through a different slit in separate universes. Shouldn't the interference only occur if the particle is traveling through both slits simultaneously in the same universe?

3) My third problem with MW is that it really does away with the concept of probability although many quantum experiments have shown that the concept does exist. For example, take a weighted coin which is 99% more likely to flip heads, than tails. CI predicts that a 100 flips would yield 99 heads and 1 tail. With a single flip, one is much more likely to get a head than a tail. However with MW, one flip will result in head in one universe, tail in another so therefore 50-50 probability.

Can someone help me to understand these issues any better? Thanks!

Finally. I found someone who agrees.

I think along the same logic.

What is the chance that we live in the one universe were NONE of the crazy but possible outcomes happen. We seem to be made of what is predicted will happen.

 

[notnews32]

My question for many-worlds proponents would be how the laws of quantum mechanics are reconciled in these outliar universes. How can intelligent life observe these fundamental laws of nature for which we have accounted for 100% of possible outcomes given that they do not observe the same distribution of outcomes that we do? Would you suggest that there is no universe in which every event is unprobable, and that these unprobable events scatter themselves through an infinite number of universes?

 

[kith]

If you agree with the MWI you also have to acknowledge that the laws of physics appear different in a very small fraction of the multiverse. I don't think this is a problem for a person who accepts the existence many worlds in the first place.

You can also expand this idea. What forbids that the laws of physics can actually be different in other universes? Maybe your universe is a very unlikely one and you only perceive it to be normal, because you need very special conditions for the emergence of the ability to perceive? (->anthropic principle)

Such verbal ramblings can be done endlessly with a MWI background. This is probably why it is so popular in pop science.

 

[Ken G]

If you agree with the MWI you also have to acknowledge that the laws of physics appear different in a very small fraction of the multiverse. I don't think this is a problem for a person who accepts the existence many worlds in the first place.

Is it essential to accept a multiverse if you accept MWI? In my view, those two ideas are quite different, and you could have either one without the other (though holding one certainly makes it easier to hold the other!). The multiverse is used to "explain" why the parameters (and maybe even laws) of our universe are what they are, within the "landscape" of other possibilities. The "many worlds" are not the multiverse, they would be aspects of a single universe with a single set of parameters and laws, but many islands of mutually incoherent processing agents trying to figure out those laws. All of the "many worlds" would have the same cosmological parameters, for example, because I don't think those parameters are thought of as dynamically evolving in statistically distributed ways, but rather as being stochastically distributed over the multiverse right from the start, independently of any subsequent evolution. That's my understanding anyway, it all seems a bit far-fetched to me and I'm not sure if I could even count anthropic reasoning as an "explanation" of how things are, but merely as an observation that must be true. Explanations shouldn't have to be true.

You can also expand this idea. What forbids that the laws of physics can actually be different in other universes? Maybe your universe is a very unlikely one and you only perceive it to be normal, because you need very special conditions for the emergence of the ability to perceive? (->anthropic principle)

Right, and that's what makes it so hard to use anthropic reasoning for anything constructive-- can we really say what the distribution is we are selecting from? Are universes that obey laws likely or unlikely? If life that thinks in ways that leads to anthropic principles requires a universe that obeys laws, how could we ever tell if we are in a majority or minority universe just because ours appears to respect laws? And does ours really respect laws, or is it natural that intelligence finds something that it can interpret that way?

 

[bohm2]

This is another paper that just came out today discussing some of the arguably less well-known criticisms against MWI:

The Many World Interpretation is therefore rather a No World Interpretation (according to the simple factorization), or a Many Many Worlds Interpretation (because each of the arbitrary more complicated factorizations tells a different story about Many Worlds...The state vector of the universe in the EI (Everett Interpretation)has no environment or observer it can relate to, and is therefore completely meaningless. The appearance of interacting subsystems of the universe are only due to a choice of a “samsara” basis, which is however completely arbitrary, just like a slicing of Minkowski spacetime is possible, which makes it look like an expanding universe . One has to add something to give the state vector and QM a meaning.

Nothing happens in the Universe of the Everett Interpretation
http://lanl.arxiv.org/pdf/1210.8447.pdf

 

[Hurkyl]

The appearance of interacting subsystems of the universe are only due to a choice of a “samsara” basis, which is however completely arbitrary, just like a slicing of Minkowski spacetime is possible, which makes it look like an expanding universe . One has to add something to give the state vector and QM a meaning.

Based on your quote, the abstract, and skimming the introduction, there is a very straightforward response to the paper: it forgot about dynamics.

 

[Demystifier]

Based on your quote, the abstract, and skimming the introduction, there is a very straightforward response to the paper: it forgot about dynamics.

Dynamics is nothing but a unitary transformation from one point in the Hilbert space to another. As long as all points in the Hilbert space look the same (which is one of central claims in the paper), such dynamics does not bring anything interesting.

 

[Quantumental]

Based on your quote, the abstract, and skimming the introduction, there is a very straightforward response to the paper: it forgot about dynamics.

Forgot about dynamics? He mentions dynamics specifically 11 times.

 

[Quantumental]

Dynamics is nothing but a unitary transformation from one point in the Hilbert space to another. As long as all points in the Hilbert space look the same (which is one of central claims in the paper), such dynamics does not bring anything interesting.

What are your take on the paper?
Seems to be a very interesting one, but seeing as how many papers have been written about MWI I struggle to believe he has found a new "fatal" flaw

 

[Demystifier]

What are your take on the paper?
Seems to be a very interesting one, but seeing as how many papers have been written about MWI I struggle to believe he has found a new "fatal" flaw

I have similar feelings, but let me not further comment it before I study it in detail.

 

[Dmitry67]

The appearance of interacting subsystems of the universe are only due to a choice of a “samsara” basis, which is however completely arbitrary

It is not arbitrary: there is an "unfair" selection of basis with "consciousness", whatever it means. If we accept AP in cosmology we should also accept the similar principle in MWI, there is nothing wrong with it.

 

[Demystifier]

It is not arbitrary: there is an "unfair" selection of basis with "consciousness", whatever it means. If we accept AP in cosmology we should also accept the similar principle in MWI, there is nothing wrong with it.

I don't think that many adherents of MWI would agree that consciousness is the key to solve the basis problem.

 

[martinbn]

I am probably missing something very basic, but it seems to me that the point that the vectors of the same norm all look the same is very important, at the same time he points out that the theory comes with more than just the Hilbert space, there is a distinguished operator (the Hamiltonian). That operator gives extra structure, the vectors don't look the same any more, some are eigenvectors some are not, for example. So it isn't true that the vectors look the same. This may be irrelevant for his arguments but at least as far as I read he did not make any comment on it. Also why is the factorization needed? They way I understand the MWI, very superficially, factorizations have nothing to do with the interpretation.