Examining the Myth of Decoherence & the Measurement Problem

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In summary, decoherence is often touted as the solution to the "measurement problem" in quantum mechanics, but upon closer inspection, it appears to be nothing more than a practical tool for working with the theory. The majority of physicists do not believe that decoherence actually resolves the "measurement problem" and view it as a glorified FAPP (for all practical purposes) construct. Even among the minority who claim it does resolve foundational issues, there are alternative approaches and evidence that this is not a definitive solution. There is also a concern about the politics behind different interpretations of quantum mechanics and how they may influence the understanding of reality and existence."
  • #36


Coldcall said:
But the odds that a universal wave function evolves a viable Unicorn-inhabited universe before the one with microbes makes it almost impossible. Let's face it, the unicorn-centric fine tuning which would need to go into the wave function for such an outcome is highly unlikely. Our microbe universe, even though it is wildly coincidental as it is, is a darn sight more probable than a universe which spontaneously evolves unicorns as its first valid observer.

You seem to forget that in a wavefunction, if there is unitary evolution, there can be AT THE SAME TIME a component that will allow a microbe to emerge 3 billion years ago, and a very tiny component with a unicorn in it *right away*. There are no "odds" in a unitary evolving wavefunction: we simply have different terms of the wavefunction. So the statement that "our microbe universe is more probable than a unicorn universe" simply means that the coefficients of their predecessors in the wavefunction have different coefficients. But you should agree with me that it is still more probable that NO life evolves in a universe, or that a different form of life evolves in a universe. So "our" universe, when "our first microbe" came out, wasn't so very very more probable either. If, in our universe, the first microbe evolved after about 10 billion years, then you should admit that the odds that somewhere else another microbe evolved after just 9 billion years isn't so remotely impossible - the odds must be comparable, which means that their precursor terms in the universal wavefunction had comparable amplitudes. Early unicorns had precursors with smaller amplitudes, but they were nevertheless there.

But now you are telling me that in order for a precursor term in the wavefunction to develop a living thing, and hence to collapse out all other precursor terms, that term must have a respectable amplitude. Small terms, even though they have evolved highly sophisticated living creatures, are not capable of collapse. That saves us from the early unicorn. It can nevertheless make disappear other precursor terms, with even larger or comparable amplitudes, as long as they didn't evolve enough living material at that moment, although they would have evolved microbes, but they were just a bit late.

Now still more difficult. What is "earlier" and what is "later" depends on the frame of reference. Imagine two precursor universe terms in a neck-to-neck race in the unitary evolution to make the first microbe (and hence to collapse away the competition). Let's call them "term15" and "term208". Suppose that they make their first microbe on a spacelike interval, and on planets in different motions (remember that each precursor term now describes an entire universe: the planet on which the microbe that appear in term15 appears, doesn't even have to exist in term208. The microbe in term15 is a totally different creature than the microbe in term208, different genetic code, etc... Now, from the frame of reference of the microbe in term15, it appears to be the "first". It is of course the only one in term15. But if it maps the universe described in term208 into its own spacetime, then it is "earlier" than the event that corresponds to the microbe creation in term208, at least in its own frame of reference.
And now we look at term208. In this term, there's also a microbe created. When it goes through the same exercise as did the microbe in term15, then it comes to the conclusion that, in ITS frame of reference, it came first ! It is of course the only microbe in its entire universe described by term208, but if it maps the event in the universe of term15 into ITS spacetime, then in ITS frame of reference, it came first.

So, who wins ? What universe is now going to disappear, what microbe will never have come into existence because its precursor term of its universe was collapsed away by the awareness of the other ?
 
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  • #37


Vanesch,

"...So "our" universe, when "our first microbe" came out, wasn't so very very more probable either. If, in our universe, the first microbe evolved after about 10 billion years, then you should admit that the odds that somewhere else another microbe evolved after just 9 billion years isn't so remotely impossible - the odds must be comparable, which means that their precursor terms in the universal wavefunction had comparable amplitudes. Early unicorns had precursors with smaller amplitudes, but they were nevertheless there."

I think you think i am claiming that our universe is the only that has come about in this way or it was the first or last. I assume this is a repeating process going on "out there" so for all we know there are new viable (observer inhabited) universes springing up of which we would be unaware. Your argument against this idea seems based on the selection of histories and why there was not a unicorn inhabited universe. I can't answer that because i don't know what it would take for initial bb conditions to make such a universe and it appears to me to be far more "impossible" than ours. Quantum mechanics does appear to operate in a sort of logical manner in that historical consistency is maintained from within objective reality. Beings who evolve in a universe where unicorns appear to have been the first self-assembled biology are going to have a much harder time excplaining the flukiness than we would. What kind of universe could do that? I don't accept, if that is what you are saying, that the unicorn universe has the same probability of occurence as one which kicks off with the lesser flukey nanobe or microbe self-assembly.

But again I am not saying it couldn't happen with the unicorns. :smile:

"...So, who wins ? What universe is now going to disappear, what microbe will never have come into existence because its precursor term of its universe was collapsed away by the awareness of the other ?"

You've got me there :smile: But really I don't propose to know all the answers to PAP. If a supersposition could interfere with itself as you've described then i suppose PAP needs to find an answer. However, i think its the most elegant, self-explanatory theory for both "measruement problem" foundational issues and the anthropic conincidences (anthropic being an awful term because as you've realized i just mean biocentric really).
 
  • #38


Coldcall said:
However, i think its the most elegant, self-explanatory theory for both "measruement problem" foundational issues and the anthropic conincidences (anthropic being an awful term because as you've realized i just mean biocentric really).

In fact, you are awfully close to many worlds. The only difference between your view and "many worlds" is that certain universes have to disappear whenever there are conscient observers in other terms of the wavefunction, and that looks to me like a very strangely implementable thing: how can the arrangement of certain atoms in a certain term of the wavefunction, giving rise to a concient being (be it a microbe), suddenly make disappear other terms that describe entire universes billions of lightyears big ?
Isn't it more reasonable that these other terms just continue their happy existence ? No observable fact of their existence can in any case influence the conscient configuration, so why do they have to disappear ?

I think that from the moment you can accept "collapse" (and hence will run in any case into difficulties with relativity), then the most obvious candidate of a physical process that leads to collapse is not "conscient being" or "microbe", but rather gravity. It's actually Penrose's idea: from the moment that we have a superposition of states that have a significantly different gravitational interaction, the superposition fails and collapse must occur.
Again, from the moment that a collapse happens, you have a problem with relativity, because a collapse has to happen on a specific spacelike slice, and can't hence be a lorentz-invariant process - that's why it was easy to find a counter example with the two microbes, each one being "earlier" than the other one. So IF you can accept collapse, and hence IF you can accept a serious problem with the principles of relativity, then I think that Penrose's idea is very interesting. I'll tell you why: it avoids a fundamental difficulty with general relativity.
If you have a quantum-mechanical superposition of two gravitationally different systems, then those two states have two different spacetimes. But if you have two different spacetimes, then it is not clear at all how you are going to define a unitary time evolution operator over it! The times themselves become part of the superposition!
This is not a problem with special relativity: the spacetime in special relativity is the same for all terms, it is flat Minkowski space. So it is possible to define a unitary time evolution operator over this shared spacetime on superposed states. But that doesn't work anymore with a wavefunction in which each term has a different spacetime associated to it (because each term describes a different mass configuration). It could even be that each term by itself evolves unitarily, but with its own unitary operator, different from term to term. THAT has then the possibility to give rise to a non-unitary overall evolution, and maybe an objective collapse. That's more or less Penrose's idea.
But again, it will run into conflict with relativity, in one way or another, as ANY physical collapse scenario will. But if ever collapse is physical, I'd seriously bet on Penrose's idea.
I find it a way more attractive approach than any "living observer collapses the universe" approach.
 
  • #39


<< Yes I'm aware of his views on Bohm and i don't agree with him there, and I think the be-ables is again just another "treatment" of the problem. However he himself admitted the demise of locality, and most phycists would say hidden variables are not viable. Ironic because he falsified his own argument for hidden variables. >>

By just another "treatment" what do you happen to mean? It is true Bell more or less believed the demise of locality was inevitable. However, what most physicists would say about the viability of "hidden variable" theories is not at all reliable since most physicists are quite ignorant of this subject matter in the first place; most physicists cannot even accurately state Bell's theorem. Indeed this is also for the same basic reason that what most physicists think about the viability of, say, string field theory, is totally unreliable, because the vast majority of them do not have a formidable or even partially reliable knowledge of the technical issues involved such as covariant quantization of the string equation of motion. Also, the real experts and pioneers of QM foundations, such as de Broglie, Bohm, Bell, and others since have conclusively proven that nonlocal hidden variable theories can be constructed with minimal effort and reproduce all the empirical predictions of textbook QM. Even people like Zeh, Zurek, and Zeilinger (all anti-hidden variable physicists) admit this. Also, with regard to your last sentence, which seems to suggest that you think Bell's theorem was intended to falsify hidden variable models in general, I cannot stress this enough that Bell's theorem did not ever do such a thing. Bell was very explicit about the fact that his theorem only showed a contradiction between locally causal hidden variable theories, and the empirical predictions of standard QM and nonlocal "hidden variable" (which Bell also showed to be a misnomer) theories like the pilot wave theory or GRW collapse theory. So Bell certainly did not falsify his own arguments for hidden variables. If anything, his theory strenghtened those arguments.


<< Yes though I don't know know whether "observership" consitutes "consciousness" or vice versa. I do think its related to biology in some causal fashion. And considering we now know that quantum effects occur in biology the argument that it does not occur in our brains is unsupportable. Max Tegmark argued this in 2000 and new evidence fasilfies that argument against quantum "consciousness". That does not prove its happening but its taken away another reason for it not to be happening. >>

I agree with you about the plausibility of quantum effects being relevant to the neurobiological processes involved in consciousness. Yes, Hameroff has done a great job of compiling that empirical evidence.


<< Good questions :) But this is not my theory; it was first proposed by Wheeler in PAP. First of all, if Quantum mechanics is really fundamental to the universe then a universal wave function scenario would be quite natural. In fact Hawking & Harte have used the same idea but their conclusions don't involve the biological scope achieved by Wheeler. >>

Oh that's right. I recall it now from reading Paul Davies' book "The Mind of God".

<< As i understand the theory; In a wave of universe probabilities the one which evolves subjectively to produce the first self-evolved biological system collapses in a retro-causal manner. The microbe would be able to sense something, so the universe at that moment would be as defined or developed as was necessary for that microbe to have evolved in the probablity wave. Consistency is maintained. So in essence that first little microbe or nanobe or whatever it was held open the reality wave - our universe. I don't think the microbe has to have the "collapsing range" in the way you are looking at it. If QM, through entanglement or whatever function insists on consistency then the microbe could have very far reaching retro-causal effects. >>

So y'all want to rely on retrocausal effects from biological systems. Well, it would be quite difficult to falsify such a hypothesis. The best I could do first is ask you to justify the assumption that a microbe has some sort of "consciousness" (and define what it is), why quantum effects would be relevant to that consciousness, and what exactly is it about that consciousness that should cause wavefunctions to collapse. Also, I tend to agree with Vanesch's comments.



<< If you can point out some sort of cosmological evidence that rules out a retro-causal universe wave form i'd be interested in reading it. Wheeler's Delayed choice showed retro-causality is real. I believe the quantum eraser is kind of similar. >>

Nothing yet can rule out a retrocausal universal wavefunction. But that's quite independent from the hypothesis that retrocausality QM effects come from biological entities. I just meant cosmological evidence shows that macroscopic physical processes such as nebulae, galaxy, and star formation, and CMB radiation homogenization, occurred before any biological life did. But then you want to say that the first microbes had retrocausal influences on the universe to create this cosmological evidence. From the point of view of philosophy, that would be considered quite an overcomplicated explanation of everything we see (compared to a realist account of physics), and it would also beg the obvious question of how these microbes and eventually humans could have retrocausally constructed all this cosmological evidence and phenomena, especially these particular cosmological phenomena, as opposed to all the other possibilities that would still permit the existence of biological life (such as a universe slowing down in expansion or a smaller percentage of dark matter and a larger percentage of baryonic matter). Also, there is no reason to think that retrocausal QM effects would necessarily persist in the macroscopic classical physics domain. Indeed the evidence from classical thermodynamics and statistical mechanics shows an asymmetry in the direction of causal processes in the macroworld.

Actually, the retrocausal explanation of Wheeler's Delayed choice is only an interpretation of that experiment. There are other interpretations that do not require retrocausal effects to perfectly explain the results of that experiment, namely, the pilot wave theory. Same with the quantum eraser. So, no, those experiments don't conclusively demostrate retrocausality.




<< Just to add: Why i like this theory so much is because it

1) Accepts the observer as causal agent as every qm experiment has demonstrated.
2) Solves the biocentric tuning problem - anthropic coincidences
3) Solves the reason why it appears to be a fluke anything self-organised at all, because in a wave of universal probability, the HUP kicks in and the practically impossible becomes possible.
4) Gives a part for consciousness/awareness as opposed to zombie like machine biology. >>


As you can see, I think there are a myriad of problems and open questions to be considered before you can claim that this theory does any of 1 - 4.

That being said, I'll end with one comment that might interest you. If QM effects are significant to the neurobiological production of conscious experiences, I do think that retrocausal processes in QM could still occur and be relevant to those conscious experiences. :wink:
 
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  • #40


Vanesch,

"In fact, you are awfully close to many worlds. The only difference between your view and "many worlds" is that certain universes have to disappear whenever there are conscient observers in other terms of the wavefunction, and that looks to me like a very strangely implementable thing: how can the arrangement of certain atoms in a certain term of the wavefunction, giving rise to a concient being (be it a microbe), suddenly make disappear other terms that describe entire universes billions of lightyears big ?
Isn't it more reasonable that these other terms just continue their happy existence ? No observable fact of their existence can in any case influence the conscient configuration, so why do they have to disappear?"


Yes it is very close to Many-worlds but the difference is i don't think the many-worlds actually manifest themselves as reality. The only one which manifests itself is the one lucky enough to produce an initial observer/biological system. This can be seen as a sort of survival of the fittest universe, like a darwinian wave function in phase space. For instance in Darwinism we know that non viable organisms die out.

Why don't the other universes survive? Because if the laws of qm are based on the vitality of observer/observed relationships (as i believe the experimental evidence proves ie. two-slits) then an observer-less universe is just not viable from natures point of view. In fact its an impossibility if nature demands observers before reality can occur.

I'm not saying there aren't other universes, but if those universes also consist of a quantum mecahnical fundamental law then they must also have observers.

"...So IF you can accept collapse, and hence IF you can accept a serious problem with the principles of relativity, then I think that Penrose's idea is very interesting. I'll tell you why: it avoids a fundamental difficulty with general relativity.
If you have a quantum-mechanical superposition of two gravitationally different systems, then those two states have two different spacetimes."


I like Penroses ideas alot, and love his books, though I'm not sure how much i agree with some of his ideas. But concerning the Relativity problem you mention; my personal belief is that Relativity is not so fundamental as we are to believe. QM is the fundamental and Relativity is more of an emergent property of QM. This is why i think they currently have run into a brick wall for unifying GR and QM. They are not equals but the science community treats them as equally fundamental and they think they should just naturally snap into place together in some TOE.

I'm not saying GR does not exist and it works great on macroscopic scales but it doesn't explain gravity, it just tells us how it behaves. So for me that PAP breaks Relativity - if that is the case - is not such a problem. I seriously do not think GR will survive in its present format without being reworked to take into account the more primal QM.
 
  • #41


Maaneli,

"By just another "treatment" what do you happen to mean? It is true Bell more or less believed the demise of locality was inevitable. However, what most physicists would say about the viability of "hidden variable" theories is not at all reliable since most physicists are quite ignorant of this subject matter in the first place; most physicists cannot even accurately state Bell's theorem"

Well in relation to Bohm's ideas they are pretty far out there; re implicate order. I'm not saying he is wrong but that is a treatment of the problem which asks for an even greater leap in faith than PAP for instance.

"Also, the real experts and pioneers of QM foundations, such as de Broglie, Bohm, Bell, and others since have conclusively proven that nonlocal hidden variable theories can be constructed with minimal effort and reproduce all the empirical predictions of textbook QM. "

There were many real experts including Bohr, Heisenberg, Pauli, Wigner, Schrodinger and others with different opinions. There may be a non-local hidden variables theory that is compatible with QM but I've not heard of any conclusive evidence. Of course there is no doubt that we have yet to understand QM fully so there is plenty of room for such theories.

"I agree with you about the plausibility of quantum effects being relevant to the neurobiological processes involved in consciousness. Yes, Hameroff has done a great job of compiling that empirical evidence."

I agree. I'm a fan of Hameroff as he has stuck his neck out big time. I'm not sure the quantum process is exactly as he claims but he is probably in the right area. But he deserves some major credit for follwoing his intuition even when phycists like Tegmark attacked him. Every day we get more papers from researches indentifying quantum biological functions - even at high tempertaures.

"Oh that's right. I recall it now from reading Paul Davies' book "The Mind of God"."[/B

Actually he goes into this in a lot more detail in "goldilock's" - his most recent book. He also favours a self-explanatory type universe very similar to Wheeler's PAP. At least that's what it seems reading between the lines. I reccomend the book because he looks at all the alternatives in a fair and critical manner.

"So y'all want to rely on retrocausal effects from biological systems. Well, it would be quite difficult to falsify such a hypothesis. The best I could do first is ask you to justify the assumption that a microbe has some sort of "consciousness" (and define what it is), why quantum effects would be relevant to that consciousness, and what exactly is it about that consciousness that should cause wavefunctions to collapse. Also, I tend to agree with Vanesch's comments."

Well we know we are capable of that retro-causal effect. Delayed choice or quantum eraser epxeriment is proof of it. However, yes i cannot prove a microbe has "consciousness". Perhaps someday we will understand "consciousness" better.

"I just meant cosmological evidence shows that macroscopic physical processes such as nebulae, galaxy, and star formation, and CMB radiation homogenization, occurred before any biological life did. But then you want to say that the first microbes had retrocausal influences on the universe to create this cosmological evidence."

Yes that's correct. The stars and galaxies would have evolved in abstract first..leading to an abstract microbe, it observes and collapses the wave function into that reality. So now all those stars and galaxies and the microbe exist in reality, history having been made consistent. If we accept QM and the idea of phase space, and wave function collapse and retro-causality, and that a simple microbe is a valid observer; then this is perfectly plausible.

"Actually, the retrocausal explanation of Wheeler's Delayed choice is only an interpretation of that experiment. There are other interpretations that do not require retrocausal effects to perfectly explain the results of that experiment, namely, the pilot wave theory. Same with the quantum eraser. So, no, those experiments don't conclusively demostrate retrocausality"

I interpret it as i see it. I don't need to treat retro-causality as anything other than what it demonstrates...which is retro-causality. I know of no scientists who question the retro-causality. What they question quite rightly (and I am not suggesting otherwise) is that you cannot send signals or communicate with the past. Thats completely different than retor-causality.

If you insist on ignoring retro-causality then we might as well insist entanglement is also some kind of mirage, or keep ignoring the "measurement problem". Think about entanglement, it is clearly retro-causal as its infuence is FTL. Is entanglement not real? It is real but we can't use it to communicate - just like retro-causality in the case of PAP.

Let me ask you what is it about retro-causality that you refuse to believe is occurring?
 
  • #42


Hello, I'm a bit late in skimming this thread...

vanesch said:
Is QM simply a statistical description of some underlying process - in other words, is the quantum wave function simply some description of our knowledge about a system, and not a physical description of the system itself ? That would then explain the "collapse" as just an "update of our information" ?

This is part of my preferred "interpretation". There sure are some issues to resolve in this view, and that's why I personally consider these questions to take us back to the foundations of inductive logic.

As is known, just a plain bayesian account of quantum probabilities can not explain things like superposition. But i think the explanation is to be found in this spirit, but it's more complicated. I think we need to consider tha nature of the probability spaces, and once we account for that they are dynamical, I would not be suprised to see that the superposition pops out of there.

To me this does not represents answers, it represents a direction of research, or more like what to me seems like the most rational direction to invest research in.

vanesch said:
But it begs then the question of what IS a physical description.

As I choose to see it, the the observer IS this description (similar to Zurek's way of putting it that "what the observer knows and what the observer is" is inseparable - I like the sound of that, although it's meaning may still be a bit ambigous). This is how the observer doesn't need a brain in the biological sense. I think of the observer as a self-organised structure that has emerged as a semi-stable subsystem in a given environment.

The physical nature of a system, encodes it's opinion of it's enviroment. So rather than just thinking that matter is a placeholder for information, the placeholder itself implies information. A bit like in the way we choose howto calculate a probability, we may choose a equiprobable partition (or a partition with an arbitrary prior distribution) and then, relative to that, define a relative probability. But the very choice of the partition itself has information content as I see it.

At first sight this sounds like circular reasoning, but my opinion is that it's not circular, it can be turned into a natural evolutionary scheme, that completes the idea of inductive reasoning and logic as a basis for self-organisation.

In all this, many very interesting associations to gravity is found. For example, one gets naturally to the concept of inertia. Inertia of opinion. It takes a certain "amount" of counter evidence to bully an opinon, regardless of wether right or wrong. Perhaps gravitational attractions can even be deduced to a form of attraction between strong opinions. Clearly they both influence each other, and one would expect statistically that they would converge by negitiation.

I think this line of reasearch must be largely neglected, otherwise it's a mystery how come more progress has not been made. I think other, more simple and in the short term more promising strategies has been favoured before such more ambitious but probably more more difficult ideas. But now, I think considering the apparent "crisis" in theoretical physics, the motivation for brining the fundamental questions back on the table is soon here.

/Fredrik
 
  • #43


I have the strong impression that folk here are wandering around in a maze constructed by physicists who didn't fully appreciate what they were doing when they invented Quantum Mechanics. I've now succumbed to the urge to post something I wrote a long time ago -- my very own 2 cents worth. Here it is in all its naivety.


The most successful theory in physics is quantum mechanics. This esoteric story tells of many strange phenomena. Some lie close to its central mystery — the wave-particle duality — which is the mystery of why light and elementary bits of matter sometimes behave like waves and sometimes like the tiny nuggets of energy we call particles.

One aspect of this dichotomy is that both the position and momentum of a particle, for instance an electron, cannot be precisely measured at the same time. The measurement error in position is inversely proportional to that in momentum, as set out by Heisenberg’s famous uncertainty principle.

To understand this mystery, one must begin by accepting the obvious. Your own experience will tell you that the physical world is entirely logical and self-consistent and that, sadly, it has absolutely no room for magic or miracles. You may have heard or read about such wonders, but I am quite sure you have never seen or experienced them yourself. Despite the subjective romantic aspects of the wonderful world we live in — and the ubiquity of mumbo jumbo — magic and miracles are only secondhand myths.

The workings of the physical world, it has turned out, can best be described at a fundamental level with a language that matches nature’s logic and self-consistency. The language that we have developed for this purpose is mathematics. It has many dialects, some better suited than others to describe the natural world. And some dialects of mathematics, like certain aspects of the physical world, are somewhat alien to our everyday experience.

The excellent fit between the natural world and our mathematical descriptions of it arises simply because both are entirely logical and self-consistent entities. But this circumstance, which we ourselves have contrived, does have a downside. It can encourage folk to endow physical phenomena with the properties of the mathematical tools they use to describe them as, I believe, is the case with wave- particle duality and much of quantum mechanics.

Remember this fable?

"A horse, having a wolf as a powerful and dangerous enemy, lived in constant fear of his life. Being driven to desperation it occurred to him to seek a strong ally. Whereupon he approached a man, and offered an alliance, pointing out that the wolf was likewise an enemy of the man. The man accepted the partnership at once and offered to kill the wolf immediately, if his new partner would only co-operate by placing his greater speed at the man’s disposal. The horse was willing, and allowed the man to place bridle and saddle upon him. The man mounted, hunted down the wolf, and killed him.

"The horse, joyful and relieved, thanked the man, and said: ‘Now that our enemy is dead, remove your bridle and saddle and restore my freedom.’

"Whereupon the man laughed loudly and replied, ‘The hell you say. Giddy-ap, Dobbin,’ and applied the spurs with a will."

I believe that in this fable physical phenomena are like the horse and that our mathematical descriptions of them are like the man. The wolf is primitive ignorance. Once saddled with a particular mathematical dialect, a physical phenomenon must willy-nilly be interpreted along the lines dictated by this dialect, wherever this may logically and self consistently lead, even if in some cases (quantum mechanics and relativity) this makes physics difficult to understand in the context of everyday experience.

Let me now revisit wave-particle duality. At the heart of this mystery lies another: the constitution of the physical world, which seems to be made of tiny elementary building blocks. There is convincing evidence that our familiar physical world consists almost entirely of complexities built from only four constituents — electrons with their neutrinos and two sorts of quark. These oddly named building blocks interact in various ways by exchanging another four elementary items (photons, vector bosons, gluons and gravitons). All eight building blocks occupy what I will call the elementary milieu, a universe-wide domain of space and time defined by its elementary nature and by the mathematical description we give of it.

The elementary milieu is quite distinct in scale and nature from the mesoscopic world we live in, which is midway between the unimaginably small and the inconceivably large. We should be wary of projecting our mesoscopic perspectives on to the elementary milieu. Questions such as "what are electrons?" can only be answered by describing their properties and how you measure them, using language that may include mathematics. Such an operational answer may not satisfy everyone, but — tough titty, kitty — it is the only intelligible one we can give.

We perceive this strange milieu largely by devising and interpreting experiments in which its constituents collide and scatter. For example the position of an atom might be measured by projecting electrons at it and observing how they are scattered. The tools used — electrons — and the object being investigated — an atom — are entities in the same elementary milieu. This creates an inescapable complication: the investigating tools affect the object investigated. The situation is rather like using human beings to investigate human behaviour, an inescapable complication that makes psychology an inexact discipline.

The result is that quantities extracted from the elementary milieu vary from one experiment to another, and only statistical results can be obtained (in this case a bell-shaped distribution of measured positions).

The question now arises: what mathematical description shall be given of this result? The experiment does not stand on its own, but must be interpreted in the context of other investigations of the elementary milieu. Relevant to the example I have chosen is an experiment in which both the velocity and position of an atom are measured. Again, because object and tool belong to the same milieu, statistical results are all that can be obtained.

Suppose it is decided to use Fourier methods to analyse the bell-shaped position curve. It then turns out that the same mathematical constructs (in this case component waves, interpreted statistically as the probability of the atom’s presence) will serve to analyse the bell-shaped velocity curve, provided that their wavelength is made inversely proportional to momentum, via a constant h. Statistical measurements of position and velocity are then concisely described by the same mathematical dialect, which introduces the concept of a wave function. A horse called quantum mechanics has been saddled and mounted by a man who speaks a wave-dialect, as it were, and all of the elementary milieu must then be interpretated with the same dialect.

This choice of rider leads on to the formulation of quantum mechanics as wave mechanics, and , because both the wave-dialect and the elementary milieu are entirely logical and self-consistent entitities, wave mechanics works supremely well. For example an advanced version of it (quantum electrodynamics) can be used to correctly account for the finest details of the spectra of complex atoms.

More abstract dialects (matrix mechanics and operator methods) offer more elegant ways of describing the elementary milieu, just as in the fable the horse could be saddled and ridden by men speaking other dialects. But only the elementary milieu itself is part of the physical world. The several mathematical descriptions of it that constitute quantum mechanics are ephemeral abstractions that will endure only while we are here to make use of them.

The moral of this story is that we should not read into quantum mechanics more than it contains. We need not ask whether atoms and electrons are "really" waves or if they are "really" particles. The wave-particle duality is not a mystery; such question are just inappropriate. All we can do, for our own purposes, is to ephemerally described nature using one or other mathematical dialect. We cannot further "understand" it, or discuss what the elementary milieu "really" is. Nor need we argue about the reality of the Platonic world and other such philosophical matters, such as the reduction of the wave function by observation, and the independent existence of the world of the mind.​
 
  • #44


Coldcall said:
Maaneli,

"By just another "treatment" what do you happen to mean? It is true Bell more or less believed the demise of locality was inevitable. However, what most physicists would say about the viability of "hidden variable" theories is not at all reliable since most physicists are quite ignorant of this subject matter in the first place; most physicists cannot even accurately state Bell's theorem"

Well in relation to Bohm's ideas they are pretty far out there; re implicate order. I'm not saying he is wrong but that is a treatment of the problem which asks for an even greater leap in faith than PAP for instance.

"Also, the real experts and pioneers of QM foundations, such as de Broglie, Bohm, Bell, and others since have conclusively proven that nonlocal hidden variable theories can be constructed with minimal effort and reproduce all the empirical predictions of textbook QM. "

There were many real experts including Bohr, Heisenberg, Pauli, Wigner, Schrodinger and others with different opinions. There may be a non-local hidden variables theory that is compatible with QM but I've not heard of any conclusive evidence. Of course there is no doubt that we have yet to understand QM fully so there is plenty of room for such theories.

"I agree with you about the plausibility of quantum effects being relevant to the neurobiological processes involved in consciousness. Yes, Hameroff has done a great job of compiling that empirical evidence."

I agree. I'm a fan of Hameroff as he has stuck his neck out big time. I'm not sure the quantum process is exactly as he claims but he is probably in the right area. But he deserves some major credit for follwoing his intuition even when phycists like Tegmark attacked him. Every day we get more papers from researches indentifying quantum biological functions - even at high tempertaures.

"Oh that's right. I recall it now from reading Paul Davies' book "The Mind of God"."[/B

Actually he goes into this in a lot more detail in "goldilock's" - his most recent book. He also favours a self-explanatory type universe very similar to Wheeler's PAP. At least that's what it seems reading between the lines. I reccomend the book because he looks at all the alternatives in a fair and critical manner.

"So y'all want to rely on retrocausal effects from biological systems. Well, it would be quite difficult to falsify such a hypothesis. The best I could do first is ask you to justify the assumption that a microbe has some sort of "consciousness" (and define what it is), why quantum effects would be relevant to that consciousness, and what exactly is it about that consciousness that should cause wavefunctions to collapse. Also, I tend to agree with Vanesch's comments."

Well we know we are capable of that retro-causal effect. Delayed choice or quantum eraser epxeriment is proof of it. However, yes i cannot prove a microbe has "consciousness". Perhaps someday we will understand "consciousness" better.

"I just meant cosmological evidence shows that macroscopic physical processes such as nebulae, galaxy, and star formation, and CMB radiation homogenization, occurred before any biological life did. But then you want to say that the first microbes had retrocausal influences on the universe to create this cosmological evidence."

Yes that's correct. The stars and galaxies would have evolved in abstract first..leading to an abstract microbe, it observes and collapses the wave function into that reality. So now all those stars and galaxies and the microbe exist in reality, history having been made consistent. If we accept QM and the idea of phase space, and wave function collapse and retro-causality, and that a simple microbe is a valid observer; then this is perfectly plausible.

"Actually, the retrocausal explanation of Wheeler's Delayed choice is only an interpretation of that experiment. There are other interpretations that do not require retrocausal effects to perfectly explain the results of that experiment, namely, the pilot wave theory. Same with the quantum eraser. So, no, those experiments don't conclusively demostrate retrocausality"

I interpret it as i see it. I don't need to treat retro-causality as anything other than what it demonstrates...which is retro-causality. I know of no scientists who question the retro-causality. What they question quite rightly (and I am not suggesting otherwise) is that you cannot send signals or communicate with the past. Thats completely different than retor-causality.

If you insist on ignoring retro-causality then we might as well insist entanglement is also some kind of mirage, or keep ignoring the "measurement problem". Think about entanglement, it is clearly retro-causal as its infuence is FTL. Is entanglement not real? It is real but we can't use it to communicate - just like retro-causality in the case of PAP.

Let me ask you what is it about retro-causality that you refuse to believe is occurring?




Coldcall,

<< Well in relation to Bohm's ideas they are pretty far out there; re implicate order. I'm not saying he is wrong but that is a treatment of the problem which asks for an even greater leap in faith than PAP for instance. >>

There are a lot of myths and misunderstandings about the concrete aspects of deBB and the speculative aspects of it. Bohm's idea of implicate order was nothing more than the nonlocal physics of the quantum potential, while the explicate order was nothing more than the fact that in the quantum-classical limit, the physical world appears to be composed of local physical processes. The duality of the implicate and explicate order was just the statement that nonlocal causal processes are ubiquitous in the microphysical world we don't easily observe, and it gives rise to the appearance of local physical processes in the macroworld we do easily observe. That's all. Bohm just couched it in fancy mystical language. But it certainly isn't far out when properly understood. It's just a verbal statement of the mathematics of his pilot wave theory.


<< There were many real experts including Bohr, Heisenberg, Pauli, Wigner, Schrodinger and others with different opinions. There may be a non-local hidden variables theory that is compatible with QM but I've not heard of any conclusive evidence. >>

Well among Bohr, Hesienberg, Pauli, Wigner, or Schroedinger, Pauli actually did eventually admit all the way back in 1953 that Bohm's theory was empirically equivalent with standard QM. The others never provided any criticisms of the actually physics of the theory, nor did they claim it was empirically wrong. Bohr, Heisenberg, and Wigner just objected to the philosophical idea of realism in QM. Schroedinger just detested the nonlocality of the theory. But also, I should emphasize to you that in contemporary physics, and in particular the foundations of physics and philosophy of physics communities, the pilot wave theory is universally agreed to be an empirically equivalent theory to standard QM. This has been proven in a number of papers over the years, and the few challenges that have been made to empirical equivalence have later always been shown to be flawed to everyone's satisfaction (even the challengers side). Even the MWI'ers agree pilot wave theory is empirically equivalent to standard QM. So the evidence is actually quite overwhelming.

But you shouldn't have to rely on arguments from authority. If you study the theory, it immediately becomes clear why its statistical predictions are empirically equivalent to standard QM. The general proof is quite easy.

<< I agree. I'm a fan of Hameroff as he has stuck his neck out big time. I'm not sure the quantum process is exactly as he claims but he is probably in the right area. But he deserves some major credit for follwoing his intuition even when phycists like Tegmark attacked him. Every day we get more papers from researches indentifying quantum biological functions - even at high tempertaures. >>

Yes I completely agree with this assessment. I find it to be the most exciting aspect of consciousness research thus far.

<< If we accept QM and the idea of phase space, and wave function collapse and retro-causality, and that a simple microbe is a valid observer; then this is perfectly plausible. >>

I don't think one can say it is perfectly plausible yet. All the questions I raised have to be adequately answered first, at least to show that the idea is self-consistent (from which you could then infer that it is only perfectly possible, though not necessarily plausible because the term "plausible" implies that it is very likely to work, which there is no way to justify). If those questions cannot be answered, then the idea is not self-consistent and therefore not even possible.

<< I interpret it as i see it. I don't need to treat retro-causality as anything other than what it demonstrates...which is retro-causality. I know of no scientists who question the retro-causality. >>

But that's my point. It isn't proof of retrocausality because there is a perfectly valid nonlocal hidden variables explanation of the delayed choice experiment, which cannot be empirically differentiated from the retrocausality explanation of the experiment. Both explanations account for the results of that experiment. So you have no way to say one is more correct than the other. Again, let's not rely on appeals to authority. The delayed choice experiment has already been analyzed from the point of view of pilot wave theory and shown to not require retrocausality. I recommend having a look at that literature.

<< If you insist on ignoring retro-causality then we might as well insist entanglement is also some kind of mirage, or keep ignoring the "measurement problem". >>

Entanglement and the measurement problem are very real problems. As I have pointed out, the evidence for retrocausality is not nearly that strong. That doesn't mean retrocausality is impossible, but just that it is not necessary on any empirical grounds. That was another major point of Bell's theorem.

<< Think about entanglement, it is clearly retro-causal as its infuence is FTL. Is entanglement not real? >>

Oh. I think you have a misunderstanding here. FTL influences in QM or Bell's theorem does not mean retrocausality in the way you're thinking of it. I know you're probably thinking faster than light means you can travel backwards in time (like tachyons or something). But that's not how nonlocality is manifested in QM entanglement. That notion only applies to massive particles in special relativity. The nonlocality from entanglement in QM comes from the fact that two entangled wavefunctions share a common support in configuration space with respect to a common universal time t. In other words, psi(x1, x2, t), which has a dimensionality of R^3N = R^6 since there are two particles. And when a "measurement" occurs, the entangled state vectors "collapse" instantaneously (meaning at the same time t no matter how large the spatial separation between the particles in 3-space is) to one of the two possible eigenstates in the Hilbert space, each of which is the conjugate of the other. More technically, the reduction of the entangled state vectors occurs on a space-like Cauchy surface. In deBB theory, the nonlocality is made more explicit because the trajectories of the two actual particles are instantaneously codependent since they are "piloted" by the same entangled configuration space wavefunctions before and during the measurement. In terms of Bell's good old theorem, nonlocality is just the statement that the measurement outcome A at detector a is instantaneously dependent on the measurement setting at detector b, even when the two detectors and measurement events are space-like separated.

All that being said, a suitable form of retrocausality can still be constructed to violate the Bell inequality, and thus preserve locality. The price to pay is to give up the causality assumption in Bell's theorem (the assumption that the "future" or final measurement settings are "free" or random variables). There already exists a retrocausal Bohm model that does this and reproduces all the standard quantum predictions. The philospoher of physics Huw Price has also considered some self-consistent retrocausality models for QM, and written much on this subject. Ultimately, I tend to believe (but for quite different reasons) with the idea of retrocausality being superior over nonlocality, even though I'm giving you a hard time about it. :smile:

Cheers,
Maaneli
 
  • #45


oldman,

Interesting post :smile:

"...The moral of this story is that we should not read into quantum mechanics more than it contains. We need not ask whether atoms and electrons are "really" waves or if they are "really" particles. The wave-particle duality is not a mystery; such question are just inappropriate. All we can do, for our own purposes, is to ephemerally described nature using one or other mathematical dialect. We cannot further "understand" it, or discuss what the elementary milieu "really" is. Nor need we argue about the reality of the Platonic world and other such philosophical matters, such as the reduction of the wave function by observation, and the independent existence of the world of the mind."

Okay the problem is that it is slightly a misnomer to say there is a wave-particle duality. I don't mean its wrong just that when they say "wave" they are actually talking about probabilities. So a particle really is a particle once its defined or measured. I look at the wave part as something in the subjective realm, like an abstract or phase space.

I disagree with the last part of your post. I think QM demands that we start looking at physics differently that we did during the post Copernican and classical mindset. It seems to me you are saying we should ignore the observer paradox and "measurement problem". I don't see how we are going to make progress if we ignore evidential data only because it points towards ourselves or biology in general as perhaps having a more causal effect on reality than we imagined before QM was developed.
 
  • #46


Coldcall said:
But concerning the Relativity problem you mention; my personal belief is that Relativity is not so fundamental as we are to believe. QM is the fundamental and Relativity is more of an emergent property of QM.

If you take on that stance, then by far the simplest, most intuitive and straightforward view on quantum mechanics is of course Bohmian mechanics, or a variation thereof. It's almost classical physics. No living things required. No observers required. No collapse required (the wavefunction continues to evolve in a strictly unitary way in Bohmian mechanics).

I would say that almost the *only* motivation for not accepting Bohm is relativity.

Of course, once you do away with relativity (the idea that there is a 4-dim spacetime manifold, and that space and time are just ways of slicing that up with a coordinate system), you will now have to explain why nature behaves AS IF the principle of relativity were true, while it isn't.
 
  • #47


vanesch said:
Of course, once you do away with relativity (the idea that there is a 4-dim spacetime manifold, and that space and time are just ways of slicing that up with a coordinate system), you will now have to explain why nature behaves AS IF the principle of relativity were true, while it isn't.

I face the same problem in my thinking, I think QM as well as SR and GR as emergent, from the same inductive principles. And I think there will be a solution to this. If this can't be done, something is wrong with my head. But I am willing to bet it.

Statistical reasoning and manifolds may induce it's own measures and geometry, and if these measures acquire inertia then it doesn't seem out of reach that relativity is an effect of self-organisation producint a common reference system - spacetime. SR and GR could play the role of the first equilibrium relation between observers.

Interesting but immature and early ponderings, that doesn't involve QM though, are at
A. Caticha, Towards a Statistical Geometrodynamics, http://arxiv.org/abs/gr-qc/0301061

/Fredrik
 
  • #48


Maaneli,

"...But you shouldn't have to rely on arguments from authority. If you study the theory, it immediately becomes clear why its statistical predictions are empirically equivalent to standard QM. The general proof is quite easy."

I agree, for every quantum phycist there are 10 theories :smile: I am certainly open minded to Bohm's theory and i hope phycists out there work to expand on his ideas. I really believe in a plurality of reasearch and for that reason i think Lee Smolin's TTWP was a great book because it showed how physics today has become too political and driven by agendas and research grants.

Also I'm flexible in that I'd go along with any proven solution, and remember all PAP claims to explain is how we (biology) and our biocentric universe got here against all the odds - without some sort of divine intervention. Of course PAP is dependent on an observer collapses the wave function interpretation.

But hey, if they one day resolve the measurement problem and genuinely eject any need for direct or indirect (entangled) observation for wave collapse, then I will sadly give up my preferred interpretation :cry:

"Yes I completely agree with this assessment. I find it to be the most exciting aspect of consciousness research thus far."

Yes but if it can be shown that our "consciousness" really is a quantum mechanism then i believe it will strengthen the observer-essentiality of PAP or Wigner's (Consciousness Causes Collapse). One of the biggest arguments against Wigner's CCC has been that there is no evidence of a quantum brain, hence no connection between "consciousness" and quantum mechanics. If Hameroff is right and proves it i think PAP and Wigner's CCC become more viable, not less.

"If those questions cannot be answered, then the idea is not self-consistent and therefore not even possible."

The only outstanding question in concern to retro-causality is whether bacteria could perform the same function as we demonstrate during Wheeler's delayed choice or quantum eraser. That the phenomenom exists, like entanglement i don't think is arguable. It may be a symptom of some other deeper phenomenom but retro-causality and entanglement still occurs whatever its explanation.

I take the same view on the "measurement problem". Yes there may be some other explanation for why it appears that observers are essential for defining the outcome of quantum states, but for how long will we search for the answer before we accept that observer status is causal for reality to occur?

"Oh. I think you have a misunderstanding here. FTL influences in QM or Bell's theorem does not mean retrocausality in the way you're thinking of it. I know you're probably thinking faster than light means you can travel backwards in time (like tachyons or something). But that's not how nonlocality is manifested in QM entanglement. That notion only applies to massive particles in special relativity."

No misunderstanding. I am not talking about any signaling or information being sent. Retro-causality does not mean time travel or sending information backwards etc...But entanglement is basically the same as retro-causality. Kind of like acceleration is like gravity. In Wheelers delayed choice our delayed decision effects the historical outcome. In the typcial experiment about two entangled photons and measureing the polarity of one automatically fixes that of the other the twin - is retro-causality. There is no way light could travel between them and we know that photons never experience time. So anything with a quicker influence can be seen as the same mechanism we see in Delayed choice.

Once again retro-causality is perfectly legal in quantum systems and it also does not break GR.

"Ultimately, I tend to believe (but for quite different reasons) with the idea of retrocausality being superior over nonlocality, even though I'm giving you a hard time about it."

I think they are one and the same phenomenom. Both exhibit the same FTL influence.
 
  • #49


Vanesch,

"If you take on that stance, then by far the simplest, most intuitive and straightforward view on quantum mechanics is of course Bohmian mechanics, or a variation thereof. It's almost classical physics. No living things required. No observers required. No collapse required (the wavefunction continues to evolve in a strictly unitary way in Bohmian mechanics)."

I'm starting to think you and Maaneli are working in tandem - its a conspiracy! :smile:

I don't think my belief that gravity is just an emerging property of deeper qm laws means Bohm is necessarily correct. I have my own ideas about gravity and qm but they are not well formulated at this moment but suffice to say that i consider gravity to be an objective measurement of "reality". More mass, more reality. Or look at gravity as the opposite of the subjective quantum realm of probababilties. And that is why it seems like GR and QM don't work or are on opposite scale of the microscopic/macrocopic universe.

What if reality can be measured? Would not gravity be a good scale of reality versus qm subjectivity? My ideas are very young at this moment but I am working on them :smile:
 
  • #50


Coldcall said:
oldman,


I I think QM demands that we start looking at physics differently that we did during the post Copernican and classical mindset. It seems to me you are saying we should ignore the observer paradox and "measurement problem". I don't see how we are going to make progress if we ignore evidential data only because it points towards ourselves or biology in general as perhaps having a more causal effect on reality than we imagined before QM was developed.

Are you biocentric enough to imagine that 'we or biology in general' have a 'causal effect on reality' as we observe, and by doing so collapse reality's and our combined wave function, so changing everything from what it 'was' before?
 
  • #51


oldman said:
Are you biocentric enough to imagine that 'we or biology in general' have a 'causal effect on reality' as we observe, and by doing so collapse reality's and our combined wave function, so changing everything from what it 'was' before?

Yes, more or less. In other words, because our universe works on a quantum mechanical foundation it appears geared to create objectivity/reality from the interactions between observer and observed.

Perhaps other universes don't use qm as a base and in those worlds perhaps there is reality without observers but i don't see how its possible in a quantum mechanical universe such as the one we inhabit.
 
  • #52


<< But hey, if they one day resolve the measurement problem and genuinely eject any need for direct or indirect (entangled) observation for wave collapse, then I will sadly give up my preferred interpretation :cry: >>

OK, then assuming your understanding of the measurement problem is the same as that which is in the literature, I recommend looking at section 3.3 of this paper, which shows explicitly how deBB solves the measurement problem:

http://arxiv.org/PS_cache/quant-ph/pdf/0611/0611032v1.pdf

<< If Hameroff is right and proves it i think PAP and Wigner's CCC become more viable, not less. >>

I'm not sure I see that. Well, frankly, I think Hameroff and Penrose are quite incoherent about their idea for quantum consciousness. But even if consciousness is shown to be due to quantum effects, I still don't think that necessarily supports PAP or Wigner's CCC, simply because it does not necessarily establish that consciousness acts back on the state vector in such a way as to induce collapse. That would still be a remaining challenge for proponents such as yourself.

<< But entanglement is basically the same as retro-causality. Kind of like acceleration is like gravity. In Wheelers delayed choice our delayed decision effects the historical outcome. In the typcial experiment about two entangled photons and measureing the polarity of one automatically fixes that of the other the twin - is retro-causality. >>

As I said before, I agree that retrocausality is a viable explanation of entanglement, but entanglement in standard or deBB QM has nothing to do with retrocausality, even considering the delayed choice experiment. It is just that causal influences propagate superluminally via the wavefunction in configuration space that causally connects two particles. There is no retrocausality here. A truly retrocausal account of entanglement requires a modification of the standard or deBB QM formalism to incorporate a measurement theory that utilizes retrocausation. Such a thing does exist already.

<< Once again retro-causality is perfectly legal in quantum systems and it also does not break GR. >>

I don't object to retrocausality in GR, and don't see why this is brought up to begin with.

<< I think they are one and the same phenomenom. Both exhibit the same FTL influence. >>

But they don't exhibit the same FTL influence. The nonlocality in deBB theory is perfectly unambiguous and cannot be interpreted as anything than what it is. And in the case of retrocausation models such as that of Price and Sutherland, there are no FTL events.

<< There is no way light could travel between them and we know that photons never experience time. So anything with a quicker influence can be seen as the same mechanism we see in Delayed choice. >>

No that's the thing. The wavefunction is what transmits the causal influences instantaneously through configuration space; and as I described in my previous post, it has nothing to do with a retrocausal interpretation of Delayed choice.
 
  • #53


Coldcall,

Have a read of Bell's article "de Broglie-Bohm, delayed-choice double-slit experiment, and density matrix" in Speakable and Unspeakable in QM. Also have a look at his paper "Free Variables and Local Causality" in the same book, for a deeper discussion of the possiblity of retrocausality from his theorem.

Peace,
Maaneli
 
  • #54


Maaneli,

"OK, then assuming your understanding of the measurement problem is the same as that which is in the literature, I recommend looking at section 3.3 of this paper, which shows explicitly how deBB solves the measurement problem:

http://arxiv.org/PS_cache/quant-ph/p.../0611032v1.pdf" [Broken]

Thank you. I will have a good read of that and I've found some other Bohmian papers too, as you have piqued my interest.

"I'm not sure I see that. Well, frankly, I think Hameroff and Penrose are quite incoherent about their idea for quantum consciousness. But even if consciousness is shown to be due to quantum effects, I still don't think that necessarily supports PAP or Wigner's CCC, simply because it does not necessarily establish that consciousness acts back on the state vector in such a way as to induce collapse. That would still be a remaining challenge for proponents such as yourself."

Yes i think the quantum consciousness research will take a long time and I assume there will be many twists in the road. This is why I am so much in favour of different reasearch directions because the final outcome will probably contain bits of many different theories.

I'm not saying that if we prove quantum consciousness it will prove CCC. But it will falsify one of the arguments against CCC, which is that the brain doesn't do quantum consciousness because its too wet and noisey. Personally i think that roadblock for quantum consciousness has already been pulled down through recent discoveries of quantum biological functions in hot and wet environments.

Yes absolutely; if quantum consciosuness is proven then a causal connection still has to be made between our mind and the phenomenom we observe. However if we got as far as proving quantum consciosuness, then i would expect for us to also discover some very interesting properties of mind or quantum consciousness which i would hope sheds some light on how our minds may be able to collapse a wave function.

However, even Bohm, Zurek (founder of Decoherence) and others who would not necessarily accept CCC admit that a final QM solution will probably have to include "consciousness". In fact almost all scientists except super-realists admit this either publicly or privately. I just read a paper by Zeilinger who i noticed you mentioned the other day:

"Quantum World is full of paradoxes, of which the most well-known is Schrodinger's cat. There have been a number of attempts in the history of quantum physics to somehow bypass the conceptual problems of quantum physics, witness for example Albert Einstein's position. Not the least because all these attempts have turned out not to be very fruitful, the only productive approach is to accept quantum phenomena and ask what the message of the quantum really is. John Archibald Wheeler has formulated this in his far-reaching questions."

http://www.metanexus.net/ultimate_reality/zeilinger.pdf [Broken]

"As I said before, I agree that retrocausality is a viable explanation of entanglement, but entanglement in standard or deBB QM has nothing to do with retrocausality, even considering the delayed choice experiment. It is just that causal influences propagate superluminally via the wavefunction in configuration space that causally connects two particles. There is no retrocausality here. A truly retrocausal account of entanglement requires a modification of the standard or deBB QM formalism to incorporate a measurement theory that utilizes retrocausation. Such a thing does exist already"

I don't agree. Anything that can influence anything else faster than c, is in essence or atleast in relation to Relatvity a retro-causal event. It has nothing to do with interpretations of qm. Entanglement is an observable fact. Now we can argue about what it means and whether its a sub function of some deeper underlying nature but its still retro-causal. This is one of the things that bugs me about the whole QM interpretational thing, is that we appear to need to re-interpret everything so that it makes sense according to theory x, y or z.

"But they don't exhibit the same FTL influence. The nonlocality in deBB theory is perfectly unambiguous and cannot be interpreted as anything than what it is. And in the case of retrocausation models such as that of Price and Sutherland, there are no FTL events."

Yes they do. The entanglement phenomenom and the Wheelers Delayed choice both exhibit an FTL influence. I assume they are either the same thing, or caused by the same underlying fundamentals. I consider it far too much of a coincidence that we see two different independent phenomenom with FTL influence. I need to read up on deBB to see how its treated in that theory but its "treatment" in theory does not represent evidence.

Now Zeilinger has an interesting take on this in the paper i listed above. He says: "And quantum entanglement is then nothing else than the property of subsystems of a composed quantum systems to carry information jointly, independent of space and time; and the randomness of individual quantum events is a consequence of the finiteness of information."
 
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  • #55


Maaneli said:
Coldcall,

Have a read of Bell's article "de Broglie-Bohm, delayed-choice double-slit experiment, and density matrix" in Speakable and Unspeakable in QM. Also have a look at his paper "Free Variables and Local Causality" in the same book, for a deeper discussion of the possiblity of retrocausality from his theorem.

Peace,
Maaneli

Hi Maaneli,

Okay I've read a few various docs including the ones you linked to in the other posts. Its an interesting theory though i am still confused about a few areas. For instance the hidden variable part of it. I can't figure out if the theory provides one or accepts non-locality.

But the most serious problem i have with it is the idea that a particle does in fact have a definite position inside the wave function. I think there is sufficient evidence pointing to show that whatever is in that wave function its pure subjectivity, perhaps on some sort of platonic level. The reason it can be argued that it is a subjective level is because there is no time, so to speak, and this is demonstrated by our old friend "entanglement". Leaving aside the semantics of retrocausality, whatever level this entanglement exists on i would propose that time does not exist at all. So if there is no time i think there is nothing but probabilities in that wave function.

And if energy conservation is a primary insinct in qm mother nature, then it seems illogical that there would need to be any particle position already defined inside a superposition. I would think the calculation, if you will, is done on the fly - instantaneously as with "entanglement" - but not cued up, then delivered at measurement/decoherence.

See what i mean?

Regards

Coldcall
 
  • #56


Coldcall,


I don't agree. Anything that can influence anything else faster than c, is in essence or atleast in relation to Relatvity a retro-causal event.


No, that was my point before. SR in the way you're thinking of it doesn't apply to nonrelativistic QM in that way. That's just basic nonrelativistic QM. I gave you an example before of how nonlocality occurs in terms of wavefunctions entangled in configuration space in standard QM and deBB QM, which clearly showed it had nothing to do with retrocausality. Did you understand that example? Do you know mathematically what the configuration space is and what the Hilbert space is? Can you write the singlet state wavefunction in standard QM formalism? If so, please show me exactly where in my example there is retrocausality. Namely, that there are particles or waves moving backward in time, or more precisely in the negative t direction.



Yes they do. The entanglement phenomenom and the Wheelers Delayed choice both exhibit an FTL influence. I assume they are either the same thing, or caused by the same underlying fundamentals. I consider it far too much of a coincidence that we see two different independent phenomenom with FTL influence. I need to read up on deBB to see how its treated in that theory but its "treatment" in theory does not represent evidence.


You just seem to be totally disregarding everything I said earlier about no FTL influences in the deBB-QM account of Delayed choice and all other entanglement phenomena, and why that is the reason you cannot conclusively infer that Delayed choice necessarily involves backwards causation.



Now Zeilinger has an interesting take on this in the paper i listed above. He says: "And quantum entanglement is then nothing else than the property of subsystems of a composed quantum systems to carry information jointly, independent of space and time; and the randomness of individual quantum events is a consequence of the finiteness of information."

A word of advice, be very cautious with Zeilinger. He has a tendency to carelessly throw around this word "information" without defining it. Indeed, the first question you should ask about his quote is "information about what?". Moreover, "how does he define information as something on its own?". "Information" always is about something else, in other contexts. For example, the information in history books is about historical events. So what exactly could Zeilinger possibly mean there?
 
  • #57


Coldcall,


Okay I've read a few various docs including the ones you linked to in the other posts. Its an interesting theory though i am still confused about a few areas. For instance the hidden variable part of it. I can't figure out if the theory provides one or accepts non-locality.


Nonlocality and hidden variables are not in contradiction with each other. I explained that before.

In deBB, you would call the "hidden variable" the particle positions. Although, in the context of deBB, it becomes clear that the term "hidden variables" for the particle positions is a seriously bad misnomer, since in deBB it is the particles that we see in experiments and which give rise to the appearance of the classical physical world. It is the wavefunction in deBB (which is the same wavefunction as in textbook QM) that is the hidden variable since we never directly observe it like we do the particles. But, yes, because there is a configuration space wavefunction in deBB, it is a nonlocal "hidden variables" theory.


But the most serious problem i have with it is the idea that a particle does in fact have a definite position inside the wave function. I think there is sufficient evidence pointing to show that whatever is in that wave function its pure subjectivity, perhaps on some sort of platonic level.


Some people have suggested the wavefunction is nomological or epistemological, as opposed to ontological. It is still an open question. However, as you can see from the mathematics of the theory, neither possibility contradicts the idea that a particle has a definite position in space.


The reason it can be argued that it is a subjective level is because there is no time, so to speak, and this is demonstrated by our old friend "entanglement". Leaving aside the semantics of retrocausality, whatever level this entanglement exists on i would propose that time does not exist at all.


I'm sorry but this conjecture of yours makes no sense in the mathematics of entangled wavefunctions. A nonfactorizable wavefuncion, psi(x1, x2, t), clearly has a time dependence. There's no going around that. This is very basic QM, regardless of interpretations.



And if energy conservation is a primary insinct in qm mother nature, then it seems illogical that there would need to be any particle position already defined inside a superposition. I would think the calculation, if you will, is done on the fly - instantaneously as with "entanglement" - but not cued up, then delivered at measurement/decoherence.


Sorry, I honestly don't understand what question you're asking. Perhaps you could phrase it in clearer language?

~M
 
  • #58


Maaneli,

"Did you understand that example? Do you know mathematically what the configuration space is and what the Hilbert space is? Can you write the singlet state wavefunction in standard QM formalism? If so, please show me exactly where in my example there is retrocausality. Namely, that there are particles or waves moving backward in time, or more precisely in the negative t direction."

I appreciate your inviting me to show off my terrible maths skills but I'm not falling for that old chestnut :smile:

But its not necessary in any case. This is pure common sense stuff. Let me ask you a question; where does Bohmian mechanics stand on the issue of background independence? The reason i ask that is because any instantaneous action in a background independent fundamental law will be retro-causal from the perspective of our classical reality with the speed of light contraints. In entanglment we know no wave or particle passes between the pairs, but there is still a retro-causal event. How its happening we don't know but in our world the influence of our action is having an instantaneous effect even if it was light years apart. That is retro-causal. Please don't confuse it with sending messages or signals or waves or particles in the manner, its impossible within our classic universe.

"In deBB, you would call the "hidden variable" the particle positions. Although, in the context of deBB, it becomes clear that the term "hidden variables" for the particle positions is a seriously bad misnomer, since in deBB it is the particles that we see in experiments and which give rise to the appearance of the classical physical world. It is the wavefunction in deBB (which is the same wavefunction as in textbook QM) that is the hidden variable since we never directly observe it like we do the particles. But, yes, because there is a configuration space wavefunction in deBB, it is a nonlocal "hidden variables" theory"

Okay i understand this part now. Bohmian mechanics claims the hidden position has a definite value. So what is it? Its really pushing the credibility envelope to claim there is a determined value before its measured/observed. That is asking for a tremendous amount of faith in something that cannot be proved.

"Some people have suggested the wavefunction is nomological or epistemological, as opposed to ontological. It is still an open question. However, as you can see from the mathematics of the theory, neither possibility contradicts the idea that a particle has a definite position in space."

Well it could be. But once again its making some heavy speculations. I'm not against speculation as you know :smile: but its just asking me to believe something when i have opposing beliefs ( re the subjectvity within a superposition) which make more sense to me. On conjecture and speculation one is more likely to go with a theory one feels is the most logical. But I'm sure you appreciate that :smile:

"I'm sorry but this conjecture of yours makes no sense in the mathematics of entangled wavefunctions. A nonfactorizable wavefuncion, psi(x1, x2, t), clearly has a time dependence. There's no going around that. This is very basic QM, regardless of interpretations."

Once again i suspect what you are telling me is that Bohmian mechanics is a background-dependent theory? The time dependence calculation in qm is to explain the time factor in our universe - in classical terms. Most quantum gravity theorists think that any fundamental theory, string or otherwise will need to be background-independent. That means independent of space/time.

And as i pointed out before, the instantaneous "spooky action at a distance" of entanglement is prima facie evidence that qm, whatever fundamental law it is representing does not experience "time".

"Sorry, I honestly don't understand what question you're asking. Perhaps you could phrase it in clearer language?"

Okay if as Bohmian mechanics claims, that the wave function of a particle actually contains a defined value prior to measurement/observation it would seem to break conservation of energy because nature would be expending energy by having a hidden value for each and every object or particle in superpositon in the universe. Why is it necessary for nature to be called on to register (even subjectively) a hidden position? To me that seems inefficient and i don't see the point of it.

Regards

Coldcall
 
  • #59


Maaneli,

By the way, there are lots of papers on the net on "time-independent" Schrodinger equations.

Another interesting idea is testing accurately the speed of the effects of entanglement or for instance quantum tunnelling. This is hard to achieve right now because these experiments would have to be done over large enough distances where we can actually discount the classical time it took to make the measurement. In other words we need to check just the transit time post-measurement.

My prediction is that if we could achieve clean results for these tests, we'd observe zero transit time, so absolutely instantaneous, not just FTL. That would not prove, but i think it would make a strong case that qm is coming from some zero time subjective environment.
 
  • #60


Coldcall said:
Maaneli,

"Did you understand that example? Do you know mathematically what the configuration space is and what the Hilbert space is? Can you write the singlet state wavefunction in standard QM formalism? If so, please show me exactly where in my example there is retrocausality. Namely, that there are particles or waves moving backward in time, or more precisely in the negative t direction."

I appreciate your inviting me to show off my terrible maths skills but I'm not falling for that old chestnut :smile:

But its not necessary in any case. This is pure common sense stuff. Let me ask you a question; where does Bohmian mechanics stand on the issue of background independence? The reason i ask that is because any instantaneous action in a background independent fundamental law will be retro-causal from the perspective of our classical reality with the speed of light contraints. In entanglment we know no wave or particle passes between the pairs, but there is still a retro-causal event. How its happening we don't know but in our world the influence of our action is having an instantaneous effect even if it was light years apart. That is retro-causal. Please don't confuse it with sending messages or signals or waves or particles in the manner, its impossible within our classic universe.

"In deBB, you would call the "hidden variable" the particle positions. Although, in the context of deBB, it becomes clear that the term "hidden variables" for the particle positions is a seriously bad misnomer, since in deBB it is the particles that we see in experiments and which give rise to the appearance of the classical physical world. It is the wavefunction in deBB (which is the same wavefunction as in textbook QM) that is the hidden variable since we never directly observe it like we do the particles. But, yes, because there is a configuration space wavefunction in deBB, it is a nonlocal "hidden variables" theory"

Okay i understand this part now. Bohmian mechanics claims the hidden position has a definite value. So what is it? Its really pushing the credibility envelope to claim there is a determined value before its measured/observed. That is asking for a tremendous amount of faith in something that cannot be proved.

"Some people have suggested the wavefunction is nomological or epistemological, as opposed to ontological. It is still an open question. However, as you can see from the mathematics of the theory, neither possibility contradicts the idea that a particle has a definite position in space."

Well it could be. But once again its making some heavy speculations. I'm not against speculation as you know :smile: but its just asking me to believe something when i have opposing beliefs ( re the subjectvity within a superposition) which make more sense to me. On conjecture and speculation one is more likely to go with a theory one feels is the most logical. But I'm sure you appreciate that :smile:

"I'm sorry but this conjecture of yours makes no sense in the mathematics of entangled wavefunctions. A nonfactorizable wavefuncion, psi(x1, x2, t), clearly has a time dependence. There's no going around that. This is very basic QM, regardless of interpretations."

Once again i suspect what you are telling me is that Bohmian mechanics is a background-dependent theory? The time dependence calculation in qm is to explain the time factor in our universe - in classical terms. Most quantum gravity theorists think that any fundamental theory, string or otherwise will need to be background-independent. That means independent of space/time.

And as i pointed out before, the instantaneous "spooky action at a distance" of entanglement is prima facie evidence that qm, whatever fundamental law it is representing does not experience "time".

"Sorry, I honestly don't understand what question you're asking. Perhaps you could phrase it in clearer language?"

Okay if as Bohmian mechanics claims, that the wave function of a particle actually contains a defined value prior to measurement/observation it would seem to break conservation of energy because nature would be expending energy by having a hidden value for each and every object or particle in superpositon in the universe. Why is it necessary for nature to be called on to register (even subjectively) a hidden position? To me that seems inefficient and i don't see the point of it.

Regards

Coldcall




<< I appreciate your inviting me to show off my terrible maths skills but I'm not falling for that old chestnut :smile:

But its not necessary in any case. This is pure common sense stuff. >>

No but that's the thing, it isn't pure common sense stuff at all. It's very easy to make up interpretations about a physical theory if you don't have knowledge of the mathematics of the theory to constrain your range of interpretive ability. I assure you that a knowledge of the basic mathematics of QM is indispensable to being able to accurately and rigorously interpret QM.

<< Let me ask you a question; where does Bohmian mechanics stand on the issue of background independence? >>

I'm not sure. You're asking a question about deBB quantum and semiclassical gravity.

<< The reason i ask that is because any instantaneous action in a background independent fundamental law will be retro-causal from the perspective of our classical reality with the speed of light contraints. >>

Where are you getting this from? Classical physics (in the form of special relativity) is not background independent. Background independence is a property of general relativity, not special relativity. And in neither case is there retrocausality. So I don't know what you're saying.

<< In entanglment we know no wave or particle passes between the pairs, but there is still a retro-causal event. How its happening we don't know but in our world the influence of our action is having an instantaneous effect even if it was light years apart. That is retro-causal. >>

No this isn't retrocausality. Please take the time to learn the mathematics of QM. I can't debate any further with you on this until you do. Because then it is just your belief in your own interpretation (which is not based on any of the mathematics of QM) versus mine which is solidly based on mathematics of QM.

<< Please don't confuse it with sending messages or signals or waves or particles in the manner, its impossible within our classic universe. >>

What's confusing is that you're using a term (retrocausal) in a context which is totally unqualified.

<< Bohmian mechanics claims the hidden position has a definite value. So what is it? Its really pushing the credibility envelope to claim there is a determined value before its measured/observed. That is asking for a tremendous amount of faith in something that cannot be proved. >>

:confused: . That's a bizarre way of thinking! If you think it is really pushing the credibility envelope to claim there is a determined value before its measured/observed, then I guess you would say classical mechanics and classical electrodynamics are dubious theories in their domain of empirical validity because the equations of motions of particles are deterministic? I guess you would say that the moon does not have a location in space when you're not looking at it? I guess you don't believe there are probably people standing in front of you when you see them doing so with your eyes? Have you ever studied philosophy of science or epistemology at a college level? Sorry to be so shocked, but where did you get this idea that this requires a "tremendous" amount of faith? And "tremendous" compared to what else I ask you?

In any case, the position of the Bohm particle is clearly specified by the guiding equation. The way you find out about it is by knowing either the initial or final position (by making a measurement) and then running the deterministic guiding equation into the future (predicting) or the past (retrodicting) to determine the trajectory the particle took. Just like in classical mechanics and electrodynamics.

<< but its just asking me to believe something when i have opposing beliefs ( re the subjectvity within a superposition) which make more sense to me. >>

An epistemological interpretation of wavefunction superposition is not in contradiction with the idea that there is a particle with a definite position. This is also true of the Hamiltonian in classical mechanics.

<< Once again i suspect what you are telling me is that Bohmian mechanics is a background-dependent theory? The time dependence calculation in qm is to explain the time factor in our universe - in classical terms. Most quantum gravity theorists think that any fundamental theory, string or otherwise will need to be background-independent. >>

I have always been talking about nonrelativistic and relativistic QM, both of which are background-dependent theories. And I thought you were talking about them as well, not quantum gravity. In any case, there are extensions of deBB to quantum gravity and string field theory. But I am not an expert on them.


<< And as i pointed out before, the instantaneous "spooky action at a distance" of entanglement is prima facie evidence that qm, whatever fundamental law it is representing does not experience "time". >>

No you're confusing QM with quantum gravity. They are quite different theories. It is very basic QM that wavefunctions generally have time dependence. When wavefunctions have no time dependence, this is called the stationary state. I recommend learning the theory of QM before getting lost in speculations like these, as it has seriously led you astray.


<< Okay if as Bohmian mechanics claims, that the wave function of a particle actually contains a defined value prior to measurement/observation it would seem to break conservation of energy because nature would be expending energy by having a hidden value for each and every object or particle in superpositon in the universe. >>

:frown: OK. It is basic QM that wavefunctions have a deterministic and unitary evolution. That's true of the Schroedinger evolution in any interpretation. This has nothing to do with conservation of energy issues. Honestly, this can't go much further until you learn the mathematics of standard QM.

Peace,
Maaneli
 
  • #61


Maaneli said:
A word of advice, be very cautious with Zeilinger. He has a tendency to carelessly throw around this word "information" without defining it. Indeed, the first question you should ask about his quote is "information about what?". Moreover, "how does he define information as something on its own?". "Information" always is about something else, in other contexts. For example, the information in history books is about historical events. So what exactly could Zeilinger possibly mean there?

That's also my opinion. In as much as his group does brilliant experiments, I always find the section on the "interpretation" in their papers confusing (confused) as hell.
 
  • #62


Maaneli,

"No but that's the thing, it isn't pure common sense stuff at all. It's very easy to make up interpretations about a physical theory if you don't have knowledge of the mathematics of the theory to constrain your range of interpretive ability. I assure you that a knowledge of the basic mathematics of QM is indispensable to being able to accurately and rigorously interpret QM."

Well I think that's a bit of a cheap shot :smile: And exactly the reason why I stick to philosophy forums and keep this away from the physics/maths because we are talking about interpretations. I've read at least 25 different books on Quantum Mechanics and while I don't pretend to understand all the maths I certainly feel I have a reasonably good understanding of quantum theory. Or as well as i could from a non technical layman's perspective.

"Where are you getting this from? Classical physics (in the form of special relativity) is not background independent. Background independence is a property of general relativity, not special relativity. And in neither case is there retrocausality. So I don't know what you're saying."

Yes that's right, GR is BI and SR is BD. What I am arguing is that Quantum mechanics, or whatever fundamental laws our version of QM is describing is background independent. Here's the wiki entry on background independence:

"Background independence is a condition in theoretical physics, especially in quantum gravity (QG), that requires the defining equations of a theory to be independent of the actual shape of the spacetime and the value of various fields within the spacetime, and in particular to not refer to a specific coordinate system or metric. " -my emphasis added.

So what I am saying is your claim that a wave function evolves through time (from the quantum perspective) is not supportable in a background independent theory. The "time" evolution is a space/time mechanism we have bolted on for the benefit of our understanding quantum mechanics in as classical way as possible.

Okay howabout we get an experts opinion? I have a reasonable email relationship with various mathematicians/cosmologists like J.D. Barrow. I'll send him an email about whether we can assume "time" as we understand it is a property of the fundamental quantum world. Okay?

"No this isn't retrocausality. Please take the time to learn the mathematics of QM. I can't debate any further with you on this until you do. Because then it is just your belief in your own interpretation (which is not based on any of the mathematics of QM) versus mine which is solidly based on mathematics of QM"

Okay let's change the word then because you seem to have a hard time accepting retro-causality unless it amounts to particles or waves being sent backwards through time. Howabout "retro-active"? Does that make it easier for you to swallow :smile:

"That's a bizarre way of thinking! If you think it is really pushing the credibility envelope to claim there is a determined value before its measured/observed, then I guess you would say classical mechanics and classical electrodynamics are dubious theories in their domain of empirical validity because the equations of motions of particles are deterministic?"

Now I understand why you are willing to speculate wildly as Bohmian Mechanics does that there actually is a definite vlaue to the particle before its measured. Its all about clinging onto a Determinstic worldview! I'd say that is a bizarre way of thinking. What you appear to wnat to do is develop a theory which is compatible with the old classical view of nature. Why are you mixing classical Determinism with quantum mechanics? You may want a Deterministic universe because it matches your philosophical perspective but all the evidence so far suggests that view is not supportable in QM. There are atleast 2 or 3 levels of inherent indeterminism in quantum mechanics. And it seems the only way Bohmiam mechanics deals with the uncertaintly is to claim there is none, and the certainty is just hidden from us by nature's veil.

Suggesting as you have done that quantum mechanics is a classical determinist theory (by making comparisons to Newtonian motion) flies in the face of all evidence. I don't need any maths to clock that. Your and Bohmian proponents that we must keep Determinsim at all costs is almost theological in its fervour.

"An epistemological interpretation of wavefunction superposition is not in contradiction with the idea that there is a particle with a definite position. This is also true of the Hamiltonian in classical mechanics."

Its not in contradiction because we don't know what going on in the superposition. Thats like saying that claiming aliens exist in the universe is not in contradiction to the laws of nature. Yes we know its true of classical mechanics but quantum is not classical!

"I have always been talking about nonrelativistic and relativistic QM, both of which are background-dependent theories. And I thought you were talking about them as well, not quantum gravity. In any case, there are extensions of deBB to quantum gravity and string field theory. But I am not an expert on them."

Any quantum theory is going to have to fit into the bigger picture which will have to include gravity. Hence any genuine quantum intepretation will also have to meet those same requirements for an integrated theory. I'm no expert on either ST or any other quantum gravity theories but I know one thing for sure, and that is they will have to be background independent. Meaning time-independent, and as i mentioned Shrodinger equations can now be forumated to be time-independent because of this very issue about background-independence.

"No you're confusing QM with quantum gravity. They are quite different theories. It is very basic QM that wavefunctions generally have time dependence. When wavefunctions have no time dependence, this is called the stationary state. I recommend learning the theory of QM before getting lost in speculations like these, as it has seriously led you astray."

No I am not confusing anything. I'm making the point that any final theory and Quantum mechanics is far from complete, as is our understanding of gravity. For heavens sakes you don't know whether time exists in a wave function! That is not speculation!

Yes i am speculating that because of the FTL effects of entanglement being instantaneous, even across 10 billion light years, i think there is no "time" as we understand it within the real quantum fundamentals. Can you not understand that the reality we experience with time is forever tied to Relativity no qauntum mechanics?

Yes i realize that Bohmian mechanics attempts to normalise quantum mechanics into some classical facade for the sake of our simple minds. Thanks but i don't need a synthetic reading of quantum mecahnics just because it suits a classical determinist view.

Its funny you go on about maths but you are more wed to your philosophical inclinations than i.
 
  • #63


Maaneli,

About your claim that we know quantum experiences time. I looked this up in my nw version of John Barrow's "New Theories of everything".

Under the chapter title: "The Quantum mystery of Time"

He starts the first paragrapgh by saying:

"In quantum theory the status of time is an even greater mystery than it appeared to Einstein and Newton. IF it exists in a transcedent way then it is not one of those quantities subject to the famous Uncertainty Principle of Heisenberg..."

Okay? Just plain english and common sense. And from a great mathematician too :smile:
I guess he should go back to school and learn more maths because he doesn't agree with your point about classical time being applied to quantum fundamentals?
 
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  • #64
deterministic indeterminism

I didn't follow all this thread and maybe this point is uncalled for but.
Coldcall seems to argue in a conceptual manner in a non-mathematical way -

Maaneli said:
It is basic QM that wavefunctions have a deterministic and unitary evolution. That's true of the Schroedinger evolution in any interpretation.
Coldcall said:
Suggesting as you have done that quantum mechanics is a classical determinist theory (by making comparisons to Newtonian motion) flies in the face of all evidence. I don't need any maths to clock that.

- I'm not sure if Coldcall referred to the above of Maaneli,

if so, stadnard QM is clearly both indeterministic and deterministic at different layers. The outcome of particular measuresments can't be predicted with certainty (indeterminism), however the probability of any possible outcome is predictable with certainty (determinism), where any uncertainty of the probability goes back to the initial conditions, like in classical mechanics.

Unless it was already clear, this is what the "deterministic evolution of the wavefunction means". "Unitarity" impiles conservation of probability, ie. that the set of all possibilities at all times add upp to 1.

This is what standard QM suggest. In this sense, QM is very simple. I replaces the deductive causality of Newton, with a kind of inductive reasoning that is still deducive to spirit. It considers deductions at probability level, thereby restoring determinism.

But then you can go on and question this. And one may also question where this is entirely consistent when you try to add gravity. One can question the meaning of probability and the sense in having knowledge rather than opinion of a determinate state of the probability?

/Fredrik
 
  • #65


Fra,

"I didn't follow all this thread and maybe this point is uncalled for but.
Coldcall seems to argue in a conceptual manner in a non-mathematical way"


First of all not being a mathematician it would be foolish for me to try to pretend :smile: However i check my ideas with mathematicians and I've never ever had anyone say to me "you can't understand this because you don't have the maths".

However even taking maths into account, each and every qm interpretation is mathematically compatible with standard qm maths. Otherwise they would not be valid intepretations and one would have been picked as the "genuine" intepretation. The fact that we have so many standing intepretations means this is not about the maths, but about foundational issues.

"if so, stadnard QM is clearly both indeterministic and deterministic at different layers. The outcome of particular measuresments can't be predicted with certainty (indeterminism), however the probability of any possible outcome is predictable with certainty (determinism), where any uncertainty of the probability goes back to the initial conditions, like in classical mechanics."

Yes I agree there is Determinism and indetermisnim at different levels of physics. But even if only one small variable in a final TOE is non-deterministic it makes the whole system non-dterministic, because once there is any uncertainty, no matter how small an initial condition, it will taint the whole system. The butterfly effect is a prime example of how one small uncertainty works its way up through a system and makes it inherently unpredictable.

And this is the nitty-gritty of interpretations such as Bohm's and others to a lesser extent. They offer no proof of a local or non-local hidden variable. In fact one of their original proponents, John Bell, falsified the local hidden variable theory in the effort of trying to prove it. So while Bell may have been a genius he was wrong about a local theory. So then Bohmians changed it to insist on a so far unexplained non-local variables theory. How convenient! I have an inate distrust of goal-post moving theories such as Bohmian mechanics. In the same way I don't trust String theory, even though its supposed to be beautiful from a mathematical point of view.

So what i am left with to think about Maaneli's ferocious defence of Bohmian mechanics which extends to stooping to a level where he claims I cannot understand because I am not a mathematician? What he is in fact defending is his unshakeable belief that our universe is 100% Determinstic.

My preference is to accept quantum mechanics with its apparent uncertainty until someone proves otherwsie, and Bohmian mechanics proves nothing other than we must have some sort of faith for the sake of an almost theological belief about Determisnim.

New reasearch sheds some light on the repellent influence a Determinstic worldview would have on humanity, which i propose anyone interested in the Determinsim vs Indeterminsim argument reads:

"Destined To Cheat? New Research Finds Free Will Can Keep Us Honest"

http://www.sciencedaily.com/releases/2008/01/080129125354.htm

So while this does not prove a non-deterministic fundamental to the universe; it surely suggests the idea of a Deterministic universe is counter-productive to human progress/evolution.

This is one of the arguments I have always made against the Determinist cause. Arguing for such a universe means that at some stage we can map out the human life on a second by second basis, prediciting how we will live, marry and die - to the utmost accuracy. In my opinion it is a preposterous suggestion. Also Determinism is one step away from predestination. And we know what that entails...

But let's pretend its all as Maaneli and other Bohmians suggest. I suppose they would say this is why the Deterministic nature of Bohmian qm is veiled from nosey humans poking around in the guts of the universe.

Right Maaneli?
 
  • #66


Coldcall, I've participated in some interpretational threads and I will pass digging deeper in here. That's not to say there aren't many interesting questions.

I am no bomhian to start so I'll pass that this time.

Bell wrote on "professional theoretical physicists ought to be able to do better". I think so too, however I disagree Bohm has the best answer.

Deymystifier is I think the one who can be thought of as the local Bohm-guru on here.

Coldcall said:
However even taking maths into account, each and every qm interpretation is mathematically compatible with standard qm maths. Otherwise they would not be valid intepretations and one would have been picked as the "genuine" intepretation. The fact that we have so many standing intepretations means this is not about the maths, but about foundational issues.

I think one should distinguish between predictions of mathematics, and the mathematics itself.

I would not say that the mathematical formalism of quantum mechanics is with certainty, uniqely determined from experiment. This is because IMO science does not progress work by deductions. It's not like some one discovered the axioms of quantum mechanics in nature. It is a "theory". But the language of the theory is that of mathematics, but that's not to say that an mathematician would solve the problems of foundatinal physics, no less than it's enough to learn a language to write best selling books. so in this respect I agree with you that mathematics per see is not the problem.

But I figure man developed mathematics for good reason. It was needed for efficient solutions of certain problems.

It could be that there exists, as many times before, a more fundamental formalism - better described by a completely different mathematical formalisms - that still yields the same predictions as QM in the correspondingly special/limiting case. So different mathematics can be consistent with other mathematics to in special cases, within experimental error.

My personal "interpretation" is almost perpendicular to the Bohmian view. I don't look to restore determinism at all levels, I rather suggest that from the scientified perspective, there is an uncertainty in the determinsm at probability level in QM. And my personal ideas will certainly change the mathematic of QM. But I think there is a good logic as to why the standard mathematics of QM is so good. So the new logic will by no means need to contradict the current one.

It is possible argue about these things without much math, but I have no choice but to agree that if you somehow ever aspire on developing your thinking into a full scale theory that can eventually persuade othre people then, what we need is a way to produce numbers that can be tested against numbers produced from measurement devices, which normally leads to mathematical theories.

I think that even for a intrinsic philosoher, some of the basic matehmatics of QM and probability theory is beneficial. You don't need a phd in math or anything. Mainly linear algebra and some calculus.

In particular basic probability theory (bayesian), is even the basis for some philosophical schools of reasoning, from evidence.

/Fredrik
 
  • #67


Fra,

"I am no bomhian to start so I'll pass that this time. Bell wrote on "professional theoretical physicists ought to be able to do better". I think so too, however I disagree Bohm has the best answer. Deymystifier is I think the one who can be thought of as the local Bohm-guru on here."

I agree with your sentiment of Bell's. He was an interesting thinker and tackled the big questions which is more than can be said for many of modern day theorists who shy away from foundational issues. I've not yet had the pleasure of meeting Deymystifier! :smile:

"But I figure man developed mathematics for good reason. It was needed for efficient solutions of certain problems."

Maths is vital for humans to conduct physics, make predictions, calculate complex problems etc..Absolutely! What I was trying to say to Maaneli was that our maths for qm is subject to our classical reality. Its a mistake to think that quantum mechanics, behind the veil of non-measurement, is evolving as we imagine it would in a classical environment with "time".

"It is possible argue about these things without much math, but I have no choice but to agree that if you somehow ever aspire on developing your thinking into a full scale theory that can eventually persuade othre people then, what we need is a way to produce numbers that can be tested against numbers produced from measurement devices, which normally leads to mathematical theories. I think that even for a intrinsic philosoher, some of the basic matehmatics of QM and probability theory is beneficial. You don't need a phd in math or anything. Mainly linear algebra and some calculus.

In particular basic probability theory (bayesian), is even the basis for some philosophical schools of reasoning, from evidence."


Yes i agree if i wanted to formulate a whole new interpetation or develop experiments then maths would be essential. But look I'm not a scientist, I left school at 17 and started my business immediately. But hey i know how to read a set of accounting books :smile: Of course I have a strong interest from a foundational point of view, and if I had the time to take a crash course in calculus i certainly would, as i admire the way mathematics can neatly deal wth "some" complex problems.

But there is a real danger when i see people hide behind maths as an excuse not to explain themselves in a logical consistent manner. We got to this situation because i simply did not agree with Maaneli's favoured interpretation so he says it must be because I'm not a mathematician.

If someone doesn't agree with my (interpretation) i certainly would not say its because its above their level of understanding.
 
  • #68


Coldcall said:
But there is a real danger when i see people hide behind maths as an excuse not to explain themselves in a logical consistent manner. We got to this situation because i simply did not agree with Maaneli's favoured interpretation so he says it must be because I'm not a mathematician.

If someone doesn't agree with my (interpretation) i certainly would not say its because its above their level of understanding.

In a way communication, is certainly a mutual thing. So if I don't understand you, or you doesn't understand me, it's a mutual problem to solve if we want to understand each other. Sometimes one party may hold the opinion that their language is standard.

Of course it could be plain difficult to explain what is usually described in mathematics, in plain english. To do that I think takes even more skill because not only do you need to understand something in one language, you have to see beyond tha language and try to convey it in a different way. Some authors of books, have it seems to have talent for that, while some are consistently very dry and focus only of the mathematics, but then they apparently have no intetion to communicate to anyone but other similar minds.

I feel that sometimes, ideas or concepts, are more easily expressed in english but the same as with languages and math, it only works if the receptor is somewhat on the same page so to speak.

/Fredrik
 
  • #69


Hi Fra,

"Of course it could be plain difficult to explain what is usually described in mathematics, in plain english. To do that I think takes even more skill because not only do you need to understand something in one language, you have to see beyond tha language and try to convey it in a different way. Some authors of books, have it seems to have talent for that, while some are consistently very dry and focus only of the mathematics, but then they apparently have no intetion to communicate to anyone but other similar minds."

Yes if there is a substantative foundational difference because of a mathematical truth, not just a re-formulation or framework, then i agree that to understand the maths would be a very helpful thing. And to use these new physical insights maths is unavoidable.

But what's interesting is that looking at the motion of planets which is a very simple conceptual idea, can also be explained in mathematics. Now if someone just looked at the maths without having been trained (or knowing that this related to the motion of planets) they would not understand what it could be telling them. However it could be reasonably well explained with a stick scraping out the idea on a sandy beach. :cool:

So you see this is why i maintain that anything that can have any real significance on our fundamental understanding about the universe, should not be difficult to explain. It may take some innovative analogies, but we are intelligent enough, and have enough imagination to understand these important concepts - without constructing barriers subject to being a mathematician.
 
  • #70


Well I think that's a bit of a cheap shot :smile: And exactly the reason why I stick to philosophy forums and keep this away from the physics/maths because we are talking about interpretations. I've read at least 25 different books on Quantum Mechanics and while I don't pretend to understand all the maths I certainly feel I have a reasonably good understanding of quantum theory. Or as well as i could from a non technical layman's perspective.


It may be a cheap shot but it's the harsh truth. Keeping to philosophy forums doesn't justify this any better. All the serious philosophers of QM know the very basic mathematics of QM (and you don't have to be a mathematician to do this) which is why they have any semblance of credibility and coherence to their ideas. It's not about what you feel you understand. Can you write down the Schroedinger equation and general wavefunction solution? And can you identify what the Hilbert space and configuration space of QM are? Look, I could tediously take the time to explain all this to you in english and some math (which I already have tried actually), but I don't have the time or patience to do that any further, because you don't seem to know some very basic prerequisites.





Yes that's right, GR is BI and SR is BD. What I am arguing is that Quantum mechanics, or whatever fundamental laws our version of QM is describing is background independent. Here's the wiki entry on background independence:

"Background independence is a condition in theoretical physics, especially in quantum gravity (QG), that requires the defining equations of a theory to be independent of the actual shape of the spacetime and the value of various fields within the spacetime, and in particular to not refer to a specific coordinate system or metric. " -my emphasis added.

So what I am saying is your claim that a wave function evolves through time (from the quantum perspective) is not supportable in a background independent theory. The "time" evolution is a space/time mechanism we have bolted on for the benefit of our understanding quantum mechanics in as classical way as possible.



Yes in a BD theory time is not fundamental. That would however be problematic for ANY interpretation of QM based on wavefunctions. Look, the nonrelativistic Schroedinger equation and the relativistic Dirac equation both have time-dependent wavefunctions. That's very standard and well known. You're asking a question about quantum gravity which is a different issue. In terms of deBB, there is nonetheless an extension of it to a BD quantum gravity theory, namely, string field theory.


Okay howabout we get an experts opinion? I have a reasonable email relationship with various mathematicians/cosmologists like J.D. Barrow. I'll send him an email about whether we can assume "time" as we understand it is a property of the fundamental quantum world. Okay?


We don't really need his opinion on this, as this is not a controversial issue at all. But, if you want to as him anything, ask him exactly this: do wavefunctions have time-dependence in standard nonrelativistic and relativistic quantum mechanics? And what is meant by a stationary state in QM?

And make sure to tell him this is not a question about quantum gravity.



Okay let's change the word then because you seem to have a hard time accepting retro-causality unless it amounts to particles or waves being sent backwards through time. Howabout "retro-active"? Does that make it easier for you to swallow :smile:


Retrocausality has a very definite meaning in the foundations of physics literature. You just seem to be ignoring that and redefining things as you feel like it. That's the problem I have with you using the word "retrocausality" to describe QM nonlocality.



Now I understand why you are willing to speculate wildly as Bohmian Mechanics does that there actually is a definite vlaue to the particle before its measured. Its all about clinging onto a Determinstic worldview! I'd say that is a bizarre way of thinking. What you appear to wnat to do is develop a theory which is compatible with the old classical view of nature. Why are you mixing classical Determinism with quantum mechanics? You may want a Deterministic universe because it matches your philosophical perspective but all the evidence so far suggests that view is not supportable in QM. There are atleast 2 or 3 levels of inherent indeterminism in quantum mechanics. And it seems the only way Bohmiam mechanics deals with the uncertaintly is to claim there is none, and the certainty is just hidden from us by nature's veil.


Once again there is nothing wildly speculative about formulating QM into a fully realist theory of physical processes. It is perfectly consistent with everything we see, unlike the solipsistic interpretations. Moreover, determinism isn't the main point of deBB or of realist formulations of QM. There are stochastic versions of deBB that are also realist theories. Also, determinisim is not something intrinsic to just classical physics. That's an example of an error you're making by not understanding the basics of QM. The Schroedinger wavefunction evolves deterministically via the Schroedinger equation. The measurement postulates are what introduce indeterminism. Of course, the measurement postulates are hopelessly vague, ad-hoc, and anthropic, and this is the cause of the measurement problem as well as the inability of standard QM to describe the quantum-classical limit. The basic deBB theory just replaces those ad-hoc measurement postulates with a mathematically precise equation of motion for a particle that depends on the deterministic wavefunction evolution, and from this is able to derive ALL the quantum statistics without further postulates or fundamental reference to human beings.


Suggesting as you have done that quantum mechanics is a classical determinist theory (by making comparisons to Newtonian motion) flies in the face of all evidence. I don't need any maths to clock that. Your and Bohmian proponents that we must keep Determinsim at all costs is almost theological in its fervour.

You missed the point entirely before. As I already explained, the determinisim has nothing to do with classical physics, but rather the determinism of wavefunction time evolution. Moreover, as I have already exlained, there are stochastic deBB theories and there is no fervor in keeping determinism. The point is that we should only be introducing stochastiticty in a theory in a mathematically and physically precise way. By the way, that is why many Bohmians like Bell are also proponents of stochastic wavefunction collapse theories like GRW.



Its not in contradiction because we don't know what going on in the superposition. Thats like saying that claiming aliens exist in the universe is not in contradiction to the laws of nature. Yes we know its true of classical mechanics but quantum is not classical!

Missed the point again. It has nothing to do with details of superposition, quantum or classical. The point is just that there is nothing mathematically inconsistent about writing down an equation of motion for a particle in terms of something mathematically abstract (like the quantum wavefunction or classical Hamiltonian). Yes of course there are differences in details that still should be explored, but that is not my point. And please don't bother to insist that it is.
 
<h2>1. What is the measurement problem in quantum mechanics?</h2><p>The measurement problem in quantum mechanics refers to the issue of how a quantum system, which exists in multiple states simultaneously, can collapse into a single state when it is observed or measured. This is in contrast to classical physics, where measurements do not affect the state of the system being measured.</p><h2>2. What is decoherence and how does it relate to the measurement problem?</h2><p>Decoherence is the process by which a quantum system interacts with its environment, causing its superposition of states to collapse into a single state. This explains why macroscopic objects appear to follow classical physics, as their interactions with the environment quickly lead to decoherence. Decoherence does not fully solve the measurement problem, but it offers a possible explanation for why we only observe one state of a quantum system.</p><h2>3. Is decoherence the only explanation for the measurement problem?</h2><p>No, there are other proposed solutions to the measurement problem, such as the Copenhagen interpretation, which states that the act of measurement itself causes the collapse of the wave function. There is also the many-worlds interpretation, which suggests that the universe splits into multiple parallel universes when a measurement is made, with each possible outcome occurring in a different universe.</p><h2>4. How do scientists study and test the concept of decoherence?</h2><p>Scientists study and test decoherence through experiments that measure the state of a quantum system and its interactions with its environment. They also use mathematical models and simulations to understand how decoherence may occur in different systems. Additionally, advancements in technology have allowed for more precise measurements of quantum systems, providing further evidence for the role of decoherence in the measurement problem.</p><h2>5. Can decoherence be applied to other fields of science?</h2><p>Yes, the concept of decoherence has been applied to other fields such as biology, chemistry, and cosmology. In biology, it has been proposed as an explanation for how living organisms maintain their quantum coherence despite interacting with their environment. In chemistry, it has been used to explain why certain reactions occur more frequently than others. In cosmology, it has been suggested as a possible explanation for the origins of the universe and the formation of large-scale structures like galaxies and clusters of galaxies.</p>

1. What is the measurement problem in quantum mechanics?

The measurement problem in quantum mechanics refers to the issue of how a quantum system, which exists in multiple states simultaneously, can collapse into a single state when it is observed or measured. This is in contrast to classical physics, where measurements do not affect the state of the system being measured.

2. What is decoherence and how does it relate to the measurement problem?

Decoherence is the process by which a quantum system interacts with its environment, causing its superposition of states to collapse into a single state. This explains why macroscopic objects appear to follow classical physics, as their interactions with the environment quickly lead to decoherence. Decoherence does not fully solve the measurement problem, but it offers a possible explanation for why we only observe one state of a quantum system.

3. Is decoherence the only explanation for the measurement problem?

No, there are other proposed solutions to the measurement problem, such as the Copenhagen interpretation, which states that the act of measurement itself causes the collapse of the wave function. There is also the many-worlds interpretation, which suggests that the universe splits into multiple parallel universes when a measurement is made, with each possible outcome occurring in a different universe.

4. How do scientists study and test the concept of decoherence?

Scientists study and test decoherence through experiments that measure the state of a quantum system and its interactions with its environment. They also use mathematical models and simulations to understand how decoherence may occur in different systems. Additionally, advancements in technology have allowed for more precise measurements of quantum systems, providing further evidence for the role of decoherence in the measurement problem.

5. Can decoherence be applied to other fields of science?

Yes, the concept of decoherence has been applied to other fields such as biology, chemistry, and cosmology. In biology, it has been proposed as an explanation for how living organisms maintain their quantum coherence despite interacting with their environment. In chemistry, it has been used to explain why certain reactions occur more frequently than others. In cosmology, it has been suggested as a possible explanation for the origins of the universe and the formation of large-scale structures like galaxies and clusters of galaxies.

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