"decoherence" - the myth

Coldcall

Vanesch,

"You now have a problem here: that cosmic first microbe (as a material structure) only appeared in certain terms in the wavefunction, at a certain time. In fact, there are terms of the wavefunction which had other microbe-states way way way before microbes appeared in "our" universe. They were just in branches with smaller complex coefficients. So how come that *they* didn't collapse the wavefunction, but our "latecomer" microbes did ?"

i think i understand what you are asking. Not sure i can answer 100% but I'll give it a try

The way I see Wheeler's PAP is that because its based on an observer-centric version of qm only once a biology has occured which is capable of meeting the requirments needed for observer status does the universal wave function collapse. So the first universe to create a microbe capable of being an observer is the one that collapses, so there cannot have been any previous microbe-states otherwise they would have come into existence instead. However that doesnt rule out that sometimes, or maybe more often than not, the microbe evolves in the superposition, the wave function collapses into a real universe and then the microbe cant reproduce and dies. hence with no observer the universe disappears down the memory hole. Like a recycling bin.

"If you reply by saying that our microbes were the first, then that's definitely not true. There WAS an immensely small amplitude to have a universe with at almost any time in the sense that the amplitude for the particles to be "by concidence" in the right configuration to make a unicorn pop out of dust at any time (even right now) wasn't strictly 0. These amplitudes are so small that they represent almost zero odds. But they are not 0."

But the odds that a universal wave function evolves a viable Unicorn-inhabited universe before the one with microbes makes it almost impossible. Lets 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.

vanesch

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 ?

Coldcall

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 cant answer that because i dont 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 dont 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 im not saying it couldn't happen with the unicorns.

".....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 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 realised i just mean biocentric really).

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 ?

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.

Maaneli

<< 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 dont 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 dont 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 dont 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, occured 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.

Coldcall

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 dont 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 dont 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 doesnt 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.

Coldcall

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.

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

Actually he goes into this in alot 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, occured 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 thats 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 dont 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 im 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 cant 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 occuring?

Fra

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

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.

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

oldman

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.

Maaneli

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 alot 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 dont 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.

Cheers,
Maaneli

Coldcall

oldman,

Interesting post

"...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 dont 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 dont 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.

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 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.

Fra

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

Coldcall

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 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

"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 dont 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. Im 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.

Coldcall

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!

I dont 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 dont 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 Im working on them

oldman

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?

Coldcall

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 dont use qm as a base and in those worlds perhaps there is reality without observers but i dont see how its possible in a quantum mechanical universe such as the one we inhabit.