The reality of Configuration space

  • Thread starter bohm2
  • Start date
  • #1
825
53

Main Question or Discussion Point

Someone suggested to me that this stuff may be more appropriate in the QM section (I’m not sure?). I think others on here have brought this up before but I thought I’d post some stuff I’ve come across that may be useful to some as a kind of an introductory reading on the ontology of configuration space. These authors have tried to present an ontology of configuration space (and the wave function). I thought these skeptical quotes by Einstein regarding this topic is an interesting introductory quote on the topic:

In order to describe multiparticle systems, Schrodinger had replaced de Broglie’s waves in 3-space with waves in configuration space, and had abandoned the notion of particle trajectories. But Einstein was dubious of this move: “The field in a many-dimensional coordinate space does not smell like something real”, and “If only the undulatory fields introduced there could be transplanted from the n-dimensional coordinate space to the 3 or 4 dimensional!
http://arxiv.org/PS_cache/arxiv/pdf/0706/0706.2661v1.pdf

If QM is supposed to be more “fundamental” than classical physics, does this suggest that configuration space is more "fundamental" than normal 3-space or (4 dimensional space-time)? If it’s more fundamental, why does the world appear to evolve in 3-space or (4 dimensional space-time)? What is the nature of this configuration space where the wave function lives in? Goldstein writes:

A second point is that for a multi-particle system the wave function (q) = (q1 ,..., qN ) is not a weird field on physical space, it’s a weird field on configuration space, the set of all hypothetical configurations of the system. For a system of more than one particle that space is not physical space. What kind of thing is this field on that space?
Reality and the Role of the Wavefunction in Quantum Theory
http://philsci-archive.pitt.edu/8470/1/rrwf01.pdf

On the Metaphysics of Quantum Mechanics
http://www.niu.edu/~vallori/Allori-OnTheMetaphysicsOfQuantumMechanics.pdf [Broken]

I’ve been reading over the various models and trying to better understand them and here is a brief summary of my basic understanding. If I messed up please correct them because I’m no expert on these views!

1. David Albert: Configuration (3N-dimensional) space realism.
The space we live in, the space in which any realistic understanding of quantum mechanics is necessarily going to depict the history of the world as playing itself out...is configuration-space. And whatever impression we have, to the contrary (whatever impression we have, say, of living in a three-dimensional space, or in a four-dimensional space-time) is somehow flatly illusory... In reality, there is just a single 3N-dimensional wavefunction, and the division of reality into separate three-dimensional objects, including organisms, is just the product of our internal representation. Thus, for Albert objects exist as single points, evolving one way or another in this very high-dimensional space.

Wave function Ontology
http://www.princeton.edu/~hhalvors/teaching/phi538_f2004/montonwfo.pdf

Problems: Why does the world appear 3-dimensional (or 4-dimensional if space-time) to us? What does N represent in 3N space (what is the space a configuration of, if not the particles)? Maudlin finds this view hard to swallow because he finds it "obscure how something happening at a point (such as a particle occupying a point or a field being concentrated near a point) could have complexly structured physical state of affairs...it is not easy to understand how those physical structures could constitute cats, or chairs, or people."

2. Monton/Lewis: 3-dimensional space is fundamental. The 3N-dimensional space is an illusion/false and wave function is only a mathematical tool.
While their arguments are somewhat different, both claim that the world really is 3-dimensional and the 3N-dimensional space is a kind of an illusion for different reasons. While Monton flatly rejects the reality of 3-N space ("the wave function is no more real than the numbers-such as 2 or p"), Lewis rules out the reality of configuration space by arguing that the "dimensionality" of configuration space defining the wavefunction is not really "spatial".

Problem: Predictions of QM depend on the 3N-dimensional space that get lost in the 3-dimensional representation (e.g. information about correlations among different parts of the system, that are experimentally observed are left out).

QM and 3-N Dimensional Space
http://spot.colorado.edu/~monton/BradleyMonton/Articles_files/qm 3n d space final.pdf

Against 3-N Dimensional space
http://spot.colorado.edu/~monton/BradleyMonton/Articles.html

Dimension and Illusion
http://philsci-archive.pitt.edu/8345/1/dimensions.pdf

Life in Configuration space
http://philsci-archive.pitt.edu/1272/

3. T. Maudlin/Goldstein: While 3N-dimensional space is a mathematical tool the wave function is "real" (in a unique way)
There are two distinct fundamental spaces (3-dimensional and 3N-dimensional), each with its own structure. What’s more, each space must possess additional structure beyond what is normally attributed to it. Further structure is needed to ground the connections between the two fundamental spaces, saying which parts and dimensions of the high-dimensional space correspond to which parts and dimensions of ordinary space, and which axes of configuration space correspond to which particle.

Problem: Adds additional fundamental structure, making it less elegant/far more complex.

Maudlin argues, that's fine, because such structure is needed to make an informationally complete description, from which "every physical fact about the situation can be recovered". With respect to the wavefunction structure, Maudlin doesn't make a commitment but suggests that it may be unlike anything else (sorta "physical"/real but in a unique/different way), kind of "in its own metaphysical category". These authors appear (if I understand them) to regard configuration space as only a mathematical tool and the wave function as nomological (a law of nature). Thus, they seem to regard the wave function as more than just a probability wave. And even though we don't have direct “access” to it, this doesn't bother them as Maudlin writes: "If our only access to the wavefunction is via its effect on the particles, and if the connection to the lived world is primarily through the particles, then we are not constrained about the physical nature of the wavefunction."

Maudlin video-Can the world be only wave-function?
http://vimeo.com/4607553

Reallity and the role of the wave function in QT
http://arxiv.org/PS_cache/arxiv/pdf/1101/1101.4575v1.pdf

4. Bohm/Hiley: The 3N-dimensional space is a "real" objective information space.
So, 3-N space is an abstract multi-dimensional "informational space" that guides a particle evolving in 3-dimensional space.

Problem: How can an "informational field" guide the particle? How does it interact with it to inform it? The field acts on the particles but particle doesn't act on the field. Brown has argued that this goes against Einstein's action-reaction principle. Einstein wrote it is "contrary to the mode of scientific thinking...to conceive of a thing...which acts itself, but which cannot be acted upon." Regardless this ontology requires far greater intrinsic complexity to be given to particles like electrons, etc. This leads to russian dolls and problem of infinite regress at. Bohm writes:

This would imply firstly that the information represented by the Schrodinger wave field is being 'carried' by a finer and subtler level of matter that has not yet been revealed more directly. But even more important, it also implies that there may be a finer and more subtle level of information that guides the Schrodinger field, as the information on the Schrodinger field guides the particles. But this in turn is a yet more subtle 'somatic' form, which is acted on by a still more subtle kind of information, and so on. Such a hierarchy could in principle go on indefinitely. This means, of course, that the current quantum mechanical laws are only simplifications and abstractions from a vast totality, of which we are only 'scratching the surface'. That is to say, in physical experiments and observations carried out thus far, deeper levels of this totality have not yet revealed themselves.
Can Mind Affect Matter Via Active Information?
http://www.mindmatter.de/resources/pdf/hileywww.pdf

Meaning and Information
http://www.implicity.org/Downloads/Bohm_meaning+information.pdf

From the Heisenberg Picture to Bohm: a New Perspective on Active Information and its relation to Shannon Information
http://www.bbk.ac.uk/tpru/BasilHiley/Vexjo2001W.pdf

5. Antony Valentini: Configuration space is "real" where wave function, a new causal agent, evolves. (his position seems somewhere in between Albert’s, Bohm's and Maudlin/Goldstein?)
He accepts reality of configuration space but not Bohm's/Hiley's 'quantum potential'. He disagrees with Goldstein and thinks the wave function is not just nomonological (a law of nature). Valentini suggests that configuration space is "real" (like Albert, it seems) and argues that the quantum wave is a new type of "causal" agent that may take some time for us to understand it, in the same way scientists had difficulties accepting the concept of "fields" when they were first introduced. So he sees an evolution (see slides in video) from forces to fields to this non-local quantum wave (which does not vary with distance and appears to be completely unaffected by matter in between). So in his scheme, the configuration space is always there where the pilot wave (a radically new kind of causal agent that is more abstract than conventional forces or fields in 3-D space) propagates.

Problem: Mixture of above ones.

Valentini video- from Perimeter Institute The nature of the wave function in deBroglie’s pilot wave theory
http://streamer.perimeterinstitute.ca/Flash/3f521d41-f0a9-4e47-a8c7-e1fd3a4c63c8/viewer.html [Broken]
 
Last edited by a moderator:

Answers and Replies

  • #2
Ken G
Gold Member
4,438
332
1. David Albert: Configuration (3N-dimensional) space realism.
The space we live in, the space in which any realistic understanding of quantum mechanics is necessarily going to depict the history of the world as playing itself out...is configuration-space. And whatever impression we have, to the contrary (whatever impression we have, say, of living in a three-dimensional space, or in a four-dimensional space-time) is somehow flatly illusory... In reality, there is just a single 3N-dimensional wavefunction, and the division of reality into separate three-dimensional objects, including organisms, is just the product of our internal representation.
I have no objection to pointing out ontological advantages to thinking in configuration space, but I see a basic inconsistency in any claim that boils down to "the ontological entities of our previous physical theories were not the real ones, but the ontological entities of our present theories are the real ones." Come on, how can any deep thinker fall into such an obvious trap?
2. Monton/Lewis: 3-dimensional space is fundamental. The 3N-dimensional space is an illusion/false and wave function is only a mathematical tool.
Same trap again, only reversed. This one boils down to "the ontological entities of our new theories can't be real because they aren't the comfortable ontological entities we had gotten used to in our previous theories, including the ones most humans develop prior to any scientific training." No traction there either, I fear!
4. Bohm/Hiley: The 3N-dimensional space is a "real" objective information space.
So, 3-N space is an abstract multi-dimensional "informational space" that guides a particle evolving in 3-dimensional space.
An abstraction guides a particle? That doesn't sound coherent. I know Bohm's views are generally self-consistent, so I'm not sure where he got this idea from. He has the pilot wave to guide the particles, but I would have to say that the pilot wave doesn't actually guide anything, the particles behave as if guided by the pilot wave-- that way our concepts are not pushing particles around in anything but how we think about the particles.

What I keep coming back to is, it is fine to imagine ontological elements as we do science. But there is never any reason to imagine these elements are real, absolute, or uniquely determined. They vary with the theory, and science shouldn't want it any other way.
 
  • #3
736
34
Someone suggested to me that this stuff may be more appropriate in the QM section (I’m not sure?). I think others on here have brought this up before but I thought I’d post some stuff I’ve come across that may be useful to some as a kind of an introductory reading on the ontology of configuration space. These authors have tried to present an ontology of configuration space (and the wave function).
Dear bohm2,

Let me add the following. nightlight noticed that the Fock space (which is a direct sum of configuration spaces for all numbers of particles) can be just an artefact of Carleman linearization (see, e.g., http://www.akhmeteli.org/akh-prepr-ws-ijqi2.pdf (an article in Int. Journ. Quantum Inf.), starting with the words "as for second-quantized theories, nightlight..." on p. 6, and the relevant references).
 
  • #4
825
53
I have no objection to pointing out ontological advantages to thinking in configuration space, but I see a basic inconsistency in any claim that boils down to "the ontological entities of our previous physical theories were not the real ones, but the ontological entities of our present theories are the real ones." Come on, how can any deep thinker fall into such an obvious trap?

What I keep coming back to is, it is fine to imagine ontological elements as we do science. But there is never any reason to imagine these elements are real, absolute, or uniquely determined. They vary with the theory, and science shouldn't want it any other way.
Here's a historical argument why taking a "realist"/ontological approach (at least provisionally) may be useful. Consider the unification of chemistry with physics, before QM. At that time physicists dismissed a lot of the models the chemists had developed as "fictions" (non-real) because they could not be accomodated with Newtonian physics. The problem was not so much that the models were not "real" but the reduction base (Newtonian physics) was wrong.

Well into the twentieth century the failure of reduction of chemistry to physics was interpreted by prominent scientists as a critically important explanatory gap, showing that chemistry provides “merely classificatory symbols that summarized the observed course of a reaction,” to quote Brock’s standard history. Kekulé, whose structural chemistry was an important step towards eventual unification of chemistry and physics, doubted that “absolute constitutions of organic molecules could ever be given”; his models and analysis of valency were to have an instrumental interpretation only, as calculating devices. Lavoisier before him believed that “the number and nature of elements [is] an unsolvable problem, capable of an infinity of solutions none of which probably accord with Nature”; “It seems extremely probable that we know nothing at all about …[the]… indivisible atoms of which matter is composed,” and never will, he believed. Kekulé seems to be saying that there is not a problem to be solved; the structural formulas are useful or not, but there is no truth of the matter. Large parts of physics were understood the same way. Poincaré went so far as to say that we adopt the molecular theory of gases only because we are familiar with the game of billiards. Boltzmann’s scientific biographer speculates that he committed suicide because of his failure to convince the scientific community to regard his theoretical account of these matters as more than a calculating system—ironically, shortly after Einstein’s work on Brownian motion and broader issues had convinced physicists of the reality of the entities he postulated.

Bohr’s model of the atom was also regarded as lacking “physical reality” by eminent scientists. In the 1920s, America’s first Nobel Prize-winning chemist dismissed talk about the real nature of chemical bonds as metaphysical “twaddle”: they are nothing more than “a very crude method of representing certain known facts about chemical reactions, a mode of representation” only, because the concept could not be reduced to physics. The rejection of that skepticism by a few leading scientists, whose views were condemned at the time as a conceptual absurdity, paved the way for the eventual unification of chemistry and physics, with Linus Pauling’s quantum-theoretic account of the chemical bond seventy years ago.
The argument, I think, is that by treating some of these mathematical objects as ontological (more "real"), it may give some insight into what direction science/physics needs to adopt in order to progress? Again, I'm not sure but it seems reasonable to me. So, for example, the contextuality and non-locality/non-separability forced upon us by the properties of this mathematical object we call the wave function (if we take the ontological view) may be trying to tell us something about the way nature/reality may be (and I'm denying our epistemic limitations here).

THE MYSTERIES OF NATURE: HOW DEEPLY HIDDEN?

http://www.journalofphilosophy.org.myaccess.library.utoronto.ca/articles/issues/106/4/1.pdf [Broken]
 
Last edited by a moderator:
  • #5
Ken G
Gold Member
4,438
332
Here's a historical argument why taking a "realist"/ontological approach (at least provisionally) may be useful. Consider the unification of chemistry with physics, before QM. At that time physicists dismissed a lot of the models the chemists had developed as "fictions" (non-real) because they could not be accomodated with Newtonian physics. The problem was not so much that the models were not "real" but the reduction base (Newtonian physics) was wrong.
But I would point to that exact same insightful example as the reason why we should not regard our ontic elements as absolute! That was the problem, the physicists were taking the Newtonian ontology as absolute, and doing wrong reasoning from that. Intead, we should treat all our ontic elements (those of both physics and chemistry) as provisional to the context in which they are useful, and further, we should always seek unification of these ontic elements. There is no law that says unifying ontic elements should work if they are absolutely true and not work if they are merely effective mental constructs! The goal of effective mental constructs is unification.
The argument, I think, is that by treating some of these mathematical objects as ontological (more "real"), it may give some insight into what direction science/physics needs to adopt in order to progress?
I absolutely agree, but note your crucial use of "treat as real". You did not say "regarding these mathematical objects as absolutely more real" than some others, for that was exactly the mistake the physicists made. It's fine to "treat" our ontic elements as real, that's just what we do in science, it's a very useful device. The point is that the understanding we achieve, using that device, is always provisional and contextual, and we should not expect to be able to transport it outside its context of usefulness. Granted, it is never obvious what the "context of usefulness" actually is, but discovering that is very much a goal of science, it is not something we need to pretend we aren't doing.

So, for example, the contextuality and non-locality/non-separability forced upon us by the properties of this mathematical object we call the wave function (if we take the ontological view) may be trying to tell us something about the way nature/reality may be (and I'm denying our epistemic limitations here).
I feel it is very much trying to tell us something, but one of the messages we should be listening to most closely is "when is this lesson applicable, and when will it lead us down a closedminded dead end?" That must always be the question in the back of the scientist's mind, when confronting ontology of any stripe.
 
  • #7
825
53
Instead, we should treat all our ontic elements (those of both physics and chemistry) as provisional to the context in which they are useful, and further, we should always seek unification of these ontic elements. There is no law that says unifying ontic elements should work if they are absolutely true and not work if they are merely effective mental constructs! The goal of effective mental constructs is unification.
Given the unification of chemistry with QM and the unification of molecular biology with chemistry (more recently), do you see any hope/hint of similar unification of mental phenomena with present-day physics or do you think that this can't happen until major changes occur in a future physics (assuming you think this can ever happen)? Do you think that perhaps by noting "some sort of theoretical inference from the character of phenomenal properties" to their underlying constituents, it may help us decide what would be required by a future theory of physics for unification to occur? I'm having trouble focusing and expressing my thoughts, so I'm not sure if this makes sense. Consider Eddington's remarks:

But in one case—namely, for the pointer readings of my own brain—I have an insight which is not limited to the evidence of the pointer readings. That insight shows that they are attached to a background of consciousness in which case I may expect that the background of other pointer readings in physics is of a nature continuous with that revealed to me in this way, even while I do not suppose that it always has the more specialized attributes of consciousness. What is certain is that in regard to my one piece of insight into the background no problem of irreconcilability arises; I have no other knowledge of the background with which to reconcile it...There is nothing to prevent the assemblage of atoms constituting a brain from being of itself a thinking (conscious, experiencing) object in virtue of that nature which physics leaves undetermined and undeterminable. If we must embed our schedule of indicator readings in some kind of background, at least let us accept the only hint we have received as to the significance of the background—namely, that it has a nature capable of manifesting itself as mental activity.
I think McGinn hints at this where he writes he writes:

I am now in a position to state the main thesis of this paper: in order to solve the mind-body problem we need, at a minimum, a new conception of space. We need a conceptual breakthrough in the way we think about the medium in which material objects exist, and hence in our conception of material objects themselves. That is the region in which our ignorance is focused: not in the details of neurophysiological activity but, more fundamentally, in how space is structured or constituted. That which we refer to when we use the word 'space' has a nature that is quite different from how we standardly conceive it to be; so different, indeed, that it is capable of 'containing' the non-spatial (as we now conceive it) phenomenon of consciousness. Things in space can generate consciousness only because those things are not, at some level, just how we conceive them to be; they harbour some hidden aspect or principle.
http://www.nyu.edu/gsas/dept/philo/courses/consciousness97/papers/ConsciousnessSpace.html
 
  • #8
Fra
3,096
144
This probably isn't what you want to hear but in http://pirsa.org/08100049 Smolin argues against the justification of timeless eternal laws and timeless state spaces (he calls the newtonian scheme), and how this relates to to "the poisoned gift of mathematics to physics".

I think the essence of that talk is that in the quest for "objectivity", there are TWO ways to think about it.

Either you just ASSUME some ontological (ie. that CAN not be scientifically inferred; and the whole meaning of ONTOLOGICAL is that you don't REQUIRE it to be!). Ie. you assume that there are eternal laws that determined the evolution of the system in time, in a timeless statespace. the argument is that this is the poisoned gift of mathematics, and it is not empirical justified science.

Or you consider an inferred consensus that is valid between the observer and it's environment or the system it interacts with. This is a epistemological construct, which gives objectivity in the sense of consensus between different observers. But this is then an emergent expectation, not a constraint - In this view, state spaces and the LAWS that rule evolution in them are merely rationally inferred empirical expectations. APPARENT objectivity is just the result of TUNING between interacting observers. But we're not talking about mysterious ad hoc fine tuning, because the TUNING is not a conicidence, it follows from the interaction.

In that talk analogis are made from social theory (which is where Unger comes in). In social systems, laws are NOT forcing constraints you can't break. They are merely expectations from the environment that unless you obey then has a price. These laws are always in motion and is the result of an negotiation process that takes place locally througout the universe. Nothing guarantees global consensus except as a kind of equilibrium.

however, such radical ideas must explain by correspondence principle the success of the newtonian scheme. And Smoling argues in that paper that the newtonian scheme does indeed work for limiting cases: small sybsystems in QM/QFT, and then of course classical mechanics (for different reasons).

All ideas are certainly not worked out the paper, but the conceptual perspective as well as some obvious problems with newtonian scheme is introduceed.

/Fredrik
 
  • #9
Ken G
Gold Member
4,438
332
Given the unification of chemistry with QM and the unification of molecular biology with chemistry (more recently), do you see any hope/hint of similar unification of mental phenomena with present-day physics or do you think that this can't happen until major changes occur in a future physics (assuming you think this can ever happen)?
I do think it can ever happen, and I do think you are characterizing it correctly-- it is a type of unification that is needed. I think we might be a ways off yet though-- I doubt I'll see it. But I do think that some future physics is going to account much more completely for the role of the physicist in the physics, and that is when the unification you speak of might be possible. Of course, who knows what new mysteries might be raised by that kind of perspective! I don't think it will go much past that unification, it might not get to an understanding of consciousness itself. How does something understand itself, does a mirror not distort and reverse?
I think McGinn hints at this where he writes he writes:
A line I like from that is "Things in space can generate consciousness only because those things are not, at some level, just how we conceive them to be; they harbour some hidden aspect or principle." I believe this statement points to the fundamental paradox of physics: when it is the similarities between how we conceive things, and however they are, that dominate our attention, then we can make progress in the conventional way, but when we take aim at the differences between our conceptions and what is, when we look for what is hidden, we face a much more difficult task. It might not just be the task of asking the right question-- it might be the task of letting go of the very things that got us this far. We may reach the end of the line of what science can do before we get to the end of what we want science to do, and if that happens, we'll need a breakthrough akin not to any in science, but instead akin to the invention of science itself.
 
  • #10
Ken G
Gold Member
4,438
332
This probably isn't what you want to hear but in http://pirsa.org/08100049 Smolin argues against the justification of timeless eternal laws and timeless state spaces (he calls the newtonian scheme), and how this relates to to "the poisoned gift of mathematics to physics".
That's funny, I just gave a seminar in which I referred to the "cult of numerogical determinacy" that essentially dates all the way back to Pythagoras, and its legacies of both value and impediment to science. It sounds like Smolin is saying something similar about the pitfalls of the newtonian scheme.
 
  • #11
Fra
3,096
144
I think Smolins and in particular Ungers (which is not a physicist, but the more radical of the two it seems) points are important, although controversial.

What Smolin has been struggling with though (and not quite succeeded with IMO) is to make something constructive and testable about of this (so as to make it a scientific statement). His Cosmological Natural Selection idea is rooted in these ideas, but I think there are better not yet unravelled ways to implement these ideas.

These ideas are particularly hard for people that seek determinsm and realism. But what if nature itself is undecidable about it's own actions, then it's a serious mistake to try to impose more decidability in our models. Not to mention that we are lead to initial value problems as well as "landscape problems" in the sense that the empistemoligal perspective simply is unable to determined WHICH deerministic rules there are (so in the end we still have undecidability).

I think the lession is to try to not project more decidability onto nature than what simply follows from a rational expectation in the empirist view.

Smolin mentions several examples and analogies that are though provocing. For example how can it possible even make SENSE to talk about eternal laws of physics, if the universe is only 14 billion years old.

The point is that the empirist context, constraints the possible confidence and thus decidability in any inference.

Now, if we can couple this idea to how nature ACTS, then we have a scientific prediction that can be tested. Smoling argues that it CAN be tested... his CNS was his attempt, now while I'm not so impressed aobut hte CNS, I am still convinced that there is alot of things to gain here.

But in most discussions here I see that this is a "hard to convey" thinking. The "newtonian scheme"-dogma is quite cemented into the minds of many physicists.

/Fredrik
 
  • #12
Ken G
Gold Member
4,438
332
These ideas are particularly hard for people that seek determinsm and realism. But what if nature itself is undecidable about it's own actions, then it's a serious mistake to try to impose more decidability in our models.
Right, and I would object to the often-made claim that "realism" requires such decidability. That's not realism, it's "decidism", close to both "determinism" and "reductionism." When realism is equated with reductionism and determinism, it isn't realism any more, it is a very narrow, almost myopic, version. That is also the objection to the PBR "mild assumptions" about a "complete set of properties" that I keep returning to. Since when is reductionism a mild assumption, or worse, a requirement of realism?

Not to mention that we are lead to initial value problems as well as "landscape problems" in the sense that the empistemoligal perspective simply is unable to determined WHICH deerministic rules there are (so in the end we still have undecidability).
I don't want to sidetrack into a discussion of the "landscape", but it gives an example of the epistemological morass one gets into when one mistakes reductionism for realism. If one swallows the claim that realism must be reducible to some complete set of physical properties, then one immediately wonders why those properties are what they are, instead of some other possible set. Instead of seeing this for what it is (the reason that the concept of a complete set of properties is an unscientific assumption because it leads to a dead end for scientifically determining why those properties are what they are), the need is felt to make the question simply go away by introducing the landscape. It's fine to make pesky questions go away, but only if it empowers the next theory by doing so (like how GR makes the pesky question "why are inertial observers special" go away). I just don't see how the landscape is a scientific theory, it smells like pure philosophy to me.

The point is that the empirist context, constraints the possible confidence and thus decidability in any inference.
Yes, that's the key point. The old model that nature somehow "contains" an infinite amount of information in any local box, but we can only access and process a finite amount of it, is logically incoherent. Information is defined by what we do with it, it has no ontological meaning.
But in most discussions here I see that this is a "hard to convey" thinking. The "newtonian scheme"-dogma is quite cemented into the minds of many physicists.
Yes, and then there's also the "shut up and calculate" types who might not recognize that a calculation is itself a kind of epistemological stance, so even characterizing what we are doing there needs to be made consistent with some larger epistemological framework. Refusing to undertake that project is accepting that we will never be able to say what we are doing, we will only be able to do it. I think that's more than the "shut up" camp is really willing to bargain for, it's a little too quiet, and nobody is really willing to be that quiet about what science is!
child: "Daddy, what do you do for a living?"
Daddy: "I shut up and calculate, so I can't tell you."
 
Last edited:
  • #13
DevilsAvocado
Gold Member
751
91
... If QM is supposed to be more “fundamental” than classical physics, does this suggest that configuration space is more "fundamental" than normal 3-space or (4 dimensional space-time)? If it’s more fundamental, why does the world appear to evolve in 3-space or (4 dimensional space-time)? What is the nature of this configuration space where the wave function lives in? Goldstein writes:
[...]
I’ve been reading over the various models and trying to better understand them and here is a brief summary of my basic understanding. If I messed up please correct them because I’m no expert on these views!

Thanks bohm2, for the links and an interesting question. I have to start where you ended - I’m absolutely no expert on these views! (And maybe I’m making a fool of myself, but who cares ;)

Configuration space? What is that?? :shy:

In classical mechanics, Configuration space is the space of possible positions that a physical system may attain, and has the structure of a manifold (aka the configuration manifold).

So in the 'classical world', Configuration space would be the 3-dimensional Euclidean space (ℝ3), right? And in Special Relativity, ℝ3 is embedded in 4-dimensional spacetime (ℝ1,3), called Minkowski space, right?

In QM we use Hilbert space (or state space) for the wavefunction (aka state vectors), described by the Schrödinger equation, which could be time-dependent or time-independent.

What’s the problem!? :confused:

Well, if the wavefunction is considered a mathematical tool and not real; there’s no problem at all (afaict). The Schrödinger equation describes the behavior of ψ, and Born interpreted ψ as related to the probability amplitude |ψ|2, i.e. the probability density of possible positions for the particle. This is the physical meaning of the wavefunction.

StationaryStatesAnimation.gif

Two stationary states and a superposition
state at the bottom


But, what about this "n-dimensional space"?? That *must* create problems!? :grumpy:

I’m not sure it does... Hilbert space includes a generalized notion of classical Euclidean space... so this should be okay, I think... And if we consider the wavefunction as just a mathematical tool, we should be very okay, I think...

Historically, Schrödinger replaced the outdated Bohr (atomic) model, with a wave equation for the electron, and standing waves representing eigenvalues λn (n = 1,2,3,...), which this lady can explain much better than me:


600px-Harmoniki.png

Spherical harmonics for the Hilbert space

Check out the Hydrogen Atom Applet in 3D for more configurations (click, drag & release, to rotate in 3D).

16ae9fp.png


2D Quantum Well Simulation for the time-dependent Schrödinger equation


So, what happens IF the wavefunction one day turns out to be REAL!?!? :devil:

Then we got problems... to begin with; what IS a real wavefunction (and probability amplitude)? Could probabilities be something 'real' or 'material'?? :bugeye:

I have no idea... and then this 'thing' with entanglement and (what then must be) non-local 'causal correlations'... and then the 'extra dimensions'... it looks tough indeed...

And to be frank – we (they) already got 'interesting problems' in finding a solution for Quantum gravity (QG), with or without real wavefunctions:
How do we describe the fundamental degrees of freedom when there is no fixed background space? -- Carlo Rovelli

General relativity is said to be background independent, i.e. there is no fixed spacetime background. QM, including quantum field theory, relies on a fixed background (non-dynamic) structure.

This is really advanced science at the frontline, and I don’t understand that much... quantization of both space and time at the Planck scale... 4D spacetime at large scales, but 2D spacetime near the Planck scale, and a fractal structure on slices of constant time... Gosh I’m lost...

If you’re interested, here’s info on Quantum geometry and different possible solutions in pipeline. (Causal Dynamical Triangulation looks fascinating)

Okay, but what is the conclusion then?? :rolleyes:

My view is that the ordinary Joe Six-pack "We all live in yellow 3D submarine, yellow 3D submarine" is already a dead parrot.

34yvcq1.jpg


We already know that ℝ3 is an illusion. Einstein’s theory of relativity shows that time dilation (difference of elapsed time between two events as measured by two observers) arises not from technical aspects of the clocks, nor from the fact that signals need time to propagate, but from the nature of spacetime itself. Both relative velocity time dilation and gravitational time dilation has been confirmed experimentally (and corrected for in the GPS system), and these phenomena will never "go away", no matter what theory comes in the future, and the same goes for other relativistic effects, like Gravitational lensing (spacetime around a massive object is curved):

450px-2004-08-a-web_print.jpg

Where is my yellow 3D submarine!? :cry:

So how could we ever 'cope' with a fundamental reality based on 'points' on a 2D plane with any finite or infinite number of dimensions, if this turns out to be the result in unify QM & GR...??

I have no good answer... maybe we could hope to make 'parallels' to Claude Monet. If you get up close at one of his later paintings, it looks like a '2D accident', without any meaning:

a48tph.jpg


But take a few steps back, and a beautiful bridge to the '3D world' emerges:

455px-Bridge_Over_a_Pond_of_Water_Lilies%2C_Claude_Monet_1899.jpg


The answer to all this could probably not be given before we know the true nature of "space", and QM + GR = True... I think...


Finally: Can we always trust our senses? Is what we perceive what’s really there? Is this a bulletproof mechanism that always gives "The Right Answer"?

Well, talking about points on a 2D plane, check this out:

Lilac-Chaser.gif

Stare at the center cross for at least 30 seconds to
experience the three phenomena of the illusion


When you stare at the cross for about 30 seconds or so, you will see three different things, in this sequence:
  1. A gap running around the circle of lilac discs.

  2. A green disc running around the circle of lilac discs in place of the gap.

  3. The green disc running around on the grey background, with the lilac discs having disappeared in sequence.
It’s an illusion, you’re cheated! What you see is not "THE TRUTH"!! :yuck: (:wink:)

(If you want to try in full screen and/or other colors, speeds, go here.)


Cheers!
DA
 
Last edited by a moderator:
  • #14
825
53
And if we consider the wavefunction as just a mathematical tool, we should be very okay, I think...
Do you think that there are good reasons why one should treat the wave function as more of a mathematical tool compared to the electric and magnetic fields of classical electromagnetism? What I mean, is there any reason why one should treat the "field" concept as more ontological/real than the wavefunction? Wasn't it really the non-locality that was largely responsible for turning off physicists (e.g. Einstein) from taking the wave function as an ontological entity/"real". Is there any reasonable way of really avoiding this non-locality/non-separability?
 
  • #15
Ken G
Gold Member
4,438
332
No, because the correlations that quantum mechanics predicts are found to hold in experiments. Hidden variables approaches require nonlocality to match that, independently of any wave function issues.
 
  • #16
736
34
Do you think that there are good reasons why one should treat the wave function as more of a mathematical tool compared to the electric and magnetic fields of classical electromagnetism? What I mean, is there any reason why one should treat the "field" concept as more ontological/real than the wavefunction? Wasn't it really the non-locality that was largely responsible for turning off physicists (e.g. Einstein) from taking the wave function as an ontological entity/"real". Is there any reasonable way of really avoiding this non-locality/non-separability?
I think there might be (see the article cited in post 3 in this thread, although the approach for the Dirac equation there can be dramatically improved - see the article in the Journ. Math. Phys. http://akhmeteli.org/wp-content/uploads/2011/08/JMAPAQ528082303_1.pdf ). Other people strongly disagree though (you may find a lengthy and sometimes fierce discussion at https://www.physicsforums.com/showthread.php?t=369328 )
 
  • #17
825
53
I think there might be (see the article cited in post 3 in this thread, although the approach for the Dirac equation there can be dramatically improved - see the article in the Journ. Math. Phys. http://akhmeteli.org/wp-content/uploads/2011/08/JMAPAQ528082303_1.pdf ). Other people strongly disagree though (you may find a lengthy and sometimes fierce discussion at https://www.physicsforums.com/showthread.php?t=369328 )
Thanks akhmeteli. What's your opinion on PBR and how do you think it affects your model?

Papers:
The quantum state cannot be interpreted statistically
http://lanl.arxiv.org/abs/1111.3328
Generalisations of the recent Pusey-Barrett-Rudolph theorem for statistical models of quantum phenomena
http://xxx.lanl.gov/abs/1111.6304
Completeness of quantum theory implies that wave functions are physical properties
http://arxiv.org/PS_cache/arxiv/pdf/1111/1111.6597v1.pdf

Popular:
Quantum theorem shakes foundations
http://www.nature.com/news/quantum-theorem-shakes-foundations-1.9392

Blogs:
http://mattleifer.info/2011/11/20/can-the-quantum-state-be-interpreted-statistically/
http://www.scottaaronson.com/blog/?p=822
http://www.fqxi.org/community/forum/topic/999
 
Last edited:
  • #18
736
34
Thanks akhmeteli. What's your opinion on PBR and how do you think it affects your model?
I am not sure I have any opinion on PBR work, and I don't think PBR affects my model directly, as the model is not statistical. It can positively affect the model indirectly though by eliminating some alternative (statistical) interpretations.
 
  • #19
825
53
No, because the correlations that quantum mechanics predicts are found to hold in experiments. Hidden variables approaches require nonlocality to match that, independently of any wave function issues.
I never understood that. I mean consider the double-slit experiment. How does one understand individual quantum processes or measurement? The whole issue of the projection postulate, etc. Isn't that non-local? One wants to say that the wave function is epistemic to avoid wave collapse as real physical process but how can one explain the interference effects without also treating the wave function as ontic?

In Bohmian mechanics, although it's argued that position is the hidden variable it's actually the wave function that's hidden because it's never "observed", except indirectly by how it affects/guides the particle (which is "observed"). But I don't understand why position measurements assume pre-existing particle positions in Bohmian while everything else is contextual: spin, momentum, energy, and other non-position “observables”.

While the dualism is arguably a problem de-Broglie/Bohmian models some argue that the Orthodox (Copenhagen) has even greater problems:

It is interesting to note that even the orthodox quantum theory (OQT, the theory originally proposed by Bohr in which there are two separate worlds: a classical and a quantum one) involves such a dual structure: what might be regarded as its primitive ontology is the classical description of macroscopic objects, including in particular pointer orientations, while the wave function serves to determine the probability relations between the successive states of these objects. In this way, also in the case of OQT, the wave function governs the behavior of the primitive ontology. An important difference, however, between OQT on the one hand and the other theories on the other is that in the latter the primitive ontology is microscopic while in the former it is macroscopic. This makes OQT rather vague, even noncommittal, since the notion of 'macroscopic' is intrinsically vague: of how many atoms need an object consist in order to be macroscopic? And, what exactly constitutes a 'classical description' of a macroscopic object.
http://www.niu.edu/~vallori/Allori-OnTheMetaphysicsOfQuantumMechanics.pdf [Broken]

I think another weirdness in the Bohmian interpretation (BM) are the 2 characteristics below. For some reason the first part doesn't bother me as much as the "empty waves" part:

A common criticism of BM is that, whereas the wavefunction has an influence on the set of particles, the particles have no influence over the wavefunction. Not only does this conflict with the universal principle for laws of physics stating that any action is matched by a reaction, it also leads to a lot of redundancy in the wavefunction. For every branch of the wavefunction containing the actual particle trajectories, there are countless other branches corresponding to every other potential ‘world’ which would have been realized had the particle positions been different. The effects of decoherence soon disable the influence of other branches on the particle trajectories, leaving much of the wavefunction redundant. Nonetheless these redundant branches are an essential element of BM.
http://arxiv.org/PS_cache/arxiv/pdf/1104/1104.1938v1.pdf
 
Last edited by a moderator:
  • #20
DevilsAvocado
Gold Member
751
91
Do you think that there are good reasons why one should treat the wave function as more of a mathematical tool compared to the electric and magnetic fields of classical electromagnetism? What I mean, is there any reason why one should treat the "field" concept as more ontological/real than the wavefunction?
I understand what you mean and it’s a good question, but just to make sure to avoid any 'confusion'; I’m not an expert and this is just my 'personal view' (for what it’s worth). Furthermore, I’m not in any 'camp' advocating this or that stance, except when there are experiments confirming what is accurate or not.

I think there are reasons in favor for the "Just a Mathematical Tool" standpoint:
  • Originally, Schrödinger did not know the nature of ψ only that his equation describes the behavior of ψ, and he tried to interpret it as a charge density (which was wrong). One would like to think that if ψ was real, this would not have been a 'problem'... it would have come 'naturally' from the logic...

  • Schrödinger used calculus for his "wave mechanics" and Werner Heisenberg used linear algebra for his "matrix mechanics". Strange enough, they both work in describing the atomic model. Schrödinger showed that the two approaches were equivalent. I don’t know if this common in science; that two different mathematical approaches could describe the same "real thing" with the same efficiency...? Nevertheless, if Schrödinger’s "wave mechanics" is real, then must also Heisenberg’s "matrix mechanics" be real... (or I am missing something very basic?). Two 'real things' describing the same 'thing'!? Huh... :uhh:

  • I don’t know about Heisenberg’s "matrix mechanics", but in Schrödinger’s ψ there is one imaginary part (i = √-1) and the square root of a negative number does not have a solution (only complex numbers).

  • If ψ is real and |ψ|2 gives the probability density of possible positions for the particle, then "the square root of the probability density" must represent something real... what on earth is that...? Could √probabilities be real?? :bugeye:

As for electric and magnetic fields of classical electromagnetism, I think there’s big difference – We can observe the effect of these fields directly.

531px-Lightning_in_Arlington.jpg


https://www.youtube.com/watch?v=iv8msBamA3M

Magnet0873.png


640px-Classical_spectacular_laser_effects.jpg


(With the reservation the electromagnetic force can be described by the exchange of virtual photons...)

Until this day; no one has ever measured or observed ψ directly, only the end result in particles like electrons and photons, etc.

However there are claims like Wave function directly measured but when you read it you’ll see that they are talking about is "weak measurements", and one of the physicists says "Measuring the wave function itself is not really thought to be a possible thing [...] It’s not really thought to be something physical".

Wasn't it really the non-locality that was largely responsible for turning off physicists (e.g. Einstein) from taking the wave function as an ontological entity/"real".
Yes, I think you’re right. For Einstein "real non-locality" would not have been appealing, considering SR, and I guess non-realism wasn’t attractive either... The ironic thing is that EPR in the extension of EPR-Bell kinda 'backfired' on Einstein ...

Is there any reasonable way of really avoiding this non-locality/non-separability?
... because Ken G is 100% right. Local Realism is a dead parrot waiting for the Grand Funeral. What’s left is non-locality and/or non-realism (non-separability).

Edit: I changed my mind, it’s 50% right, because if you dump Realism then Locality could be saved. (Don’t ask me how this works! :smile:)

Having said this, it might look like I’m in the "Just a Mathematical Tool" camp, but I’m not, because there are things that look 'strange' even in this camp:
  • Take the Double-slit experiment. We know that a wave, interfering with itself, has to pass the two slits to generate this pattern – but this wave is not real!? How does this work?? :eek:

  • Take the EPR-Bell experiment. If the wavefunction is not real, how on earth does this 'unreal thing' manipulate a particle to be correlated with its entangled twin? How does this work? What’s the name of this 'unreal mechanism'?? :confused:

  • According to the new PBR theorem a ψ-epistemic ontological model does not work, therefore if the wavefunction is not real, any hidden variables are automatically excluded, i.e. at the fundamental level; the world is unreal... and that must mean that our measuring apparatus is also unreal... which means that we are verifying our physical theories with something that is unreal = end of science...? :bugeye:

It’s quite strange...


P.S. Ask anyone who claims that Local Realism is still an option for the name of one reputable PhD who is active at an reputable institution, and involved the foundations community, who has published at least one paper in a professional peer-reviewed journal the last 10 years, claiming Local Realism is still alive.
 
Last edited by a moderator:
  • #21
Ken G
Gold Member
4,438
332
How does one understand individual quantum processes or measurement? The whole issue of the projection postulate, etc. Isn't that non-local? One wants to say that the wave function is epistemic to avoid wave collapse as real physical process but how can one explain the interference effects without also treating the wave function as ontic?
I would say that "wave function collapse" cannot be a real physical process, because real physical processes are described by observations, and wave functions are described by a theory. So it's a category error to even have them both in the same sentence. Wave function collapse is a theoretical way to understand a physical process, what the physical process is "actually doing" is anyone's guess. Indeed, I would argue that "ontic character" to any theory is always a category error, something I would call the mind projection fallacy (though for some reason I don't understand, many people seem to believe they can distinguish between a "true ontology" and the mind projection fallacy).
In Bohmian mechanics, although it's argued that position is the hidden variable it's actually the wave function that's hidden because it's never "observed", except indirectly by how it affects/guides the particle (which is "observed"). But I don't understand why position measurements assume pre-existing particle positions while everything else is contextual: spin, momentum, energy, and other non-position “observables”.
Neither do I. I don't understand why anyone would imagine that any element of a physical theory is non-contextual. Have they no knowledge of the history of science?
While the dualism is arguably a problem de-Broglie/Bohmian models some argue that the Orthodox (Copenhagen) has even greater problems:

http://www.niu.edu/~vallori/Allori-OnTheMetaphysicsOfQuantumMechanics.pdf [Broken]
I would critique that quote on several grounds. First of all, it seems to be talking about a more Heisenberg-esque view than the Bohr view, when it talks about "two worlds." It was Bohr's view that "there is no quantum world," the world of our experience is the only one that we have any authority over, for the simple reason that it is the only one that we can give meaning to via our experience and our perceptive abilities. I feel this view is almost inescapable, yet physicists try very hard to escape it anyway, and I have no idea why. Science never needed an escape from this, maybe some form of wishful thinking does.

Second, Bohr's approach has no such requirement to be able to define the meaning of "macroscopic", that is a misunderstanding of how physics works in general. Do we need to define what a "system" is before we can use physics to describe one? No we do not-- we never define what a system is, we just say "we are going to treat this situation as if it was a system", and carry on, without any kind of precise meaning of what that is. If that makes all of physics "noncommittal", so be it, but I don't think that is what is intended by that word. Similarly, Bohr's quantum mechanics has no requirement at all to be able to say how many atoms are needed for something to be considered macroscopic, instead, it just says "let us treat our apparatus as if it was macroscopic" and carry on from there.

In other words, the quote has it backward-- we do not first define what macroscopic means and then wonder if our measuring apparatus (and all of our experience) qualifies, we first establish what our expectations are about how measuring apparatuses work (and how our experience works), hang the label "macroscopic" on that with no need for any formal definition, and proceed from there. One could easily replace the term "macroscopic" with "how we experience and perceive" and there would be not one iota of difference in Bohr's approach-- and if anyone thinks physics is "noncommittal" if it cannot define "how we experience and perceive", then I'm afraid physics is just a noncommittal endeavor.
I think another weirdness in the Bohmian interpretation (BM) are the 2 characteristics below. For some reason the first part doesn't bother me as much as the "empty waves" part:
http://arxiv.org/PS_cache/arxiv/pdf/1104/1104.1938v1.pdf
I agree, the second part is the more disquieting element. Indeed I have always considered BM to be "angels on a pin". That doesn't make it wrong, but it just seems to be trying too hard to be able to interpret reality in a certain way, with no empirical justification. Almost all ideas with that flavor in the history of physics have been discarded. Principles of physics work to unify and simplify, not to add hidden elements that produce no predictive power but make it possible to hold onto prejudicial modes of thinking.
 
Last edited by a moderator:
  • #22
476
0
Someone suggested to me that this stuff may be more appropriate in the QM section (I’m not sure?). I think others on here have brought this up before but I thought I’d post some stuff I’ve come across that may be useful to some as a kind of an introductory reading on the ontology of configuration space. These authors have tried to present an ontology of configuration space (and the wave function). I thought these skeptical quotes by Einstein regarding this topic is an interesting introductory quote on the topic:



http://arxiv.org/PS_cache/arxiv/pdf/0706/0706.2661v1.pdf

If QM is supposed to be more “fundamental” than classical physics, does this suggest that configuration space is more "fundamental" than normal 3-space or (4 dimensional space-time)? If it’s more fundamental, why does the world appear to evolve in 3-space or (4 dimensional space-time)? What is the nature of this configuration space where the wave function lives in? Goldstein writes:



Reality and the Role of the Wavefunction in Quantum Theory
http://philsci-archive.pitt.edu/8470/1/rrwf01.pdf

On the Metaphysics of Quantum Mechanics
http://www.niu.edu/~vallori/Allori-OnTheMetaphysicsOfQuantumMechanics.pdf [Broken]

I’ve been reading over the various models and trying to better understand them and here is a brief summary of my basic understanding. If I messed up please correct them because I’m no expert on these views!

1. David Albert: Configuration (3N-dimensional) space realism.
The space we live in, the space in which any realistic understanding of quantum mechanics is necessarily going to depict the history of the world as playing itself out...is configuration-space. And whatever impression we have, to the contrary (whatever impression we have, say, of living in a three-dimensional space, or in a four-dimensional space-time) is somehow flatly illusory... In reality, there is just a single 3N-dimensional wavefunction, and the division of reality into separate three-dimensional objects, including organisms, is just the product of our internal representation. Thus, for Albert objects exist as single points, evolving one way or another in this very high-dimensional space.

Wave function Ontology
http://www.princeton.edu/~hhalvors/teaching/phi538_f2004/montonwfo.pdf

Problems: Why does the world appear 3-dimensional (or 4-dimensional if space-time) to us? What does N represent in 3N space (what is the space a configuration of, if not the particles)? Maudlin finds this view hard to swallow because he finds it "obscure how something happening at a point (such as a particle occupying a point or a field being concentrated near a point) could have complexly structured physical state of affairs...it is not easy to understand how those physical structures could constitute cats, or chairs, or people."

2. Monton/Lewis: 3-dimensional space is fundamental. The 3N-dimensional space is an illusion/false and wave function is only a mathematical tool.
While their arguments are somewhat different, both claim that the world really is 3-dimensional and the 3N-dimensional space is a kind of an illusion for different reasons. While Monton flatly rejects the reality of 3-N space ("the wave function is no more real than the numbers-such as 2 or p"), Lewis rules out the reality of configuration space by arguing that the "dimensionality" of configuration space defining the wavefunction is not really "spatial".

Problem: Predictions of QM depend on the 3N-dimensional space that get lost in the 3-dimensional representation (e.g. information about correlations among different parts of the system, that are experimentally observed are left out).

QM and 3-N Dimensional Space
http://spot.colorado.edu/~monton/BradleyMonton/Articles_files/qm 3n d space final.pdf

Against 3-N Dimensional space
http://spot.colorado.edu/~monton/BradleyMonton/Articles.html

Dimension and Illusion
http://philsci-archive.pitt.edu/8345/1/dimensions.pdf

Life in Configuration space
http://philsci-archive.pitt.edu/1272/

3. T. Maudlin/Goldstein: While 3N-dimensional space is a mathematical tool the wave function is "real" (in a unique way)
There are two distinct fundamental spaces (3-dimensional and 3N-dimensional), each with its own structure. What’s more, each space must possess additional structure beyond what is normally attributed to it. Further structure is needed to ground the connections between the two fundamental spaces, saying which parts and dimensions of the high-dimensional space correspond to which parts and dimensions of ordinary space, and which axes of configuration space correspond to which particle.

Problem: Adds additional fundamental structure, making it less elegant/far more complex.

Maudlin argues, that's fine, because such structure is needed to make an informationally complete description, from which "every physical fact about the situation can be recovered". With respect to the wavefunction structure, Maudlin doesn't make a commitment but suggests that it may be unlike anything else (sorta "physical"/real but in a unique/different way), kind of "in its own metaphysical category". These authors appear (if I understand them) to regard configuration space as only a mathematical tool and the wave function as nomological (a law of nature). Thus, they seem to regard the wave function as more than just a probability wave. And even though we don't have direct “access” to it, this doesn't bother them as Maudlin writes: "If our only access to the wavefunction is via its effect on the particles, and if the connection to the lived world is primarily through the particles, then we are not constrained about the physical nature of the wavefunction."

Maudlin video-Can the world be only wave-function?
http://vimeo.com/4607553

Reallity and the role of the wave function in QT
http://arxiv.org/PS_cache/arxiv/pdf/1101/1101.4575v1.pdf

4. Bohm/Hiley: The 3N-dimensional space is a "real" objective information space.
So, 3-N space is an abstract multi-dimensional "informational space" that guides a particle evolving in 3-dimensional space.

Problem: How can an "informational field" guide the particle? How does it interact with it to inform it? The field acts on the particles but particle doesn't act on the field. Brown has argued that this goes against Einstein's action-reaction principle. Einstein wrote it is "contrary to the mode of scientific thinking...to conceive of a thing...which acts itself, but which cannot be acted upon." Regardless this ontology requires far greater intrinsic complexity to be given to particles like electrons, etc. This leads to russian dolls and problem of infinite regress at. Bohm writes:



Can Mind Affect Matter Via Active Information?
http://www.mindmatter.de/resources/pdf/hileywww.pdf

Meaning and Information
http://www.implicity.org/Downloads/Bohm_meaning+information.pdf

From the Heisenberg Picture to Bohm: a New Perspective on Active Information and its relation to Shannon Information
http://www.bbk.ac.uk/tpru/BasilHiley/Vexjo2001W.pdf

5. Antony Valentini: Configuration space is "real" where wave function, a new causal agent, evolves. (his position seems somewhere in between Albert’s, Bohm's and Maudlin/Goldstein?)
He accepts reality of configuration space but not Bohm's/Hiley's 'quantum potential'. He disagrees with Goldstein and thinks the wave function is not just nomonological (a law of nature). Valentini suggests that configuration space is "real" (like Albert, it seems) and argues that the quantum wave is a new type of "causal" agent that may take some time for us to understand it, in the same way scientists had difficulties accepting the concept of "fields" when they were first introduced. So he sees an evolution (see slides in video) from forces to fields to this non-local quantum wave (which does not vary with distance and appears to be completely unaffected by matter in between). So in his scheme, the configuration space is always there where the pilot wave (a radically new kind of causal agent that is more abstract than conventional forces or fields in 3-D space) propagates.

Problem: Mixture of above ones.

Valentini video- from Perimeter Institute The nature of the wave function in deBroglie’s pilot wave theory
http://streamer.perimeterinstitute.ca/Flash/3f521d41-f0a9-4e47-a8c7-e1fd3a4c63c8/viewer.html [Broken]
Already in classical mechanics, the state of a physical system is given in a configurational space not in spacetime.

Spacetime is used in field theory, and field theory is essentially an one-body theory. Any realistic many-body theory is not formulated in a spacetime. See for instance the textbook by Schieve.
 
Last edited by a moderator:
  • #23
Ken G
Gold Member
4,438
332
[*]Take the Double-slit experiment. We know that a wave, interfering with itself, has to pass the two slits to generate this pattern – but this wave is not real!? How does this work?? :eek:
I agree with what your post was saying, so indeed I think I have answers to this list of troubling aspects of the stance you are espousing-- so you can stick to your guns! This first one is readily resolved if we simply adopt the perfectly realistic position that all physical theories borrow from mathematical structures to define their elements, and just because the mathematical structure works in experiments, that cannot prove that the elements exist anywhere but in that theory. Indeed, this has been seen over and over throughout history. That doesn't mean we shouldn't use the terms from the theory to apply to reality, it just means there is no requirement to take them too literally. The demonstrable physics doesn't care how literally we take those terms, so why should we?
[*]Take the EPR-Bell experiment. If the wavefunction is not real, how on earth does this 'unreal thing' manipulate a particle to be correlated with its entangled twin?
The very idea that anything "manipulates particles" is already an unreal thing. "Manipulation" is an obvious anthroporphism, does the wind "manipulate" the sand? Does gravity "manipulate" the expansion of the universe? The logic is backward-- stuff happens, and the "manipulation" is in how we like to think about it. There's nothing wrong with thinking in those terms, we use words like "forces manipulate objects" all the time for good reasons, but we don't need to really believe it's true. It is easy to find interpretations of the very same physics that lack those elements, so they are clearly not endemic to the physics theory.
[*]According to the new PBR theorem a ψ-epistemic ontological model does not work, therefore if the wavefunction is not real, any hidden variables are automatically excluded, i.e. at the fundamental level; the world is unreal... and that must mean that our measuring apparatus is also unreal... which means that we are verifying our physical theories with something that is unreal = end of science...? :bugeye:
This is exactly what I was complaining about in regard to the PBR theorem on a different thread-- the way they have tried to co-opt the term "real"! Look at what you just said, you said that we should conclude the world is unreal if it is not governed by ontological hidden variables. Who ever said that a real world had to be so governed? I have no idea where that assumption comes from, there is nothing in any logically self-consistent definition of "real" that requires we dictate properties to it or else it can't be real. Where do we get these properties from? Not from the real world, it is perfectly demonstrable where we get them from-- mathematical patterns, which are thoughts regulated by certain rules of mental manipulation. So somehow we are to swallow that if the world is dictated by mathematical patterns accessible to our minds, then it is real, but if it is not so describable, in absolute terms, then it is unreal? How did idealism get passed off as realism anyway? Those are usually considered to be opposite philosophies.

So stick to your guns-- physics is a fundamentally epistemic exercise, and no one should claim that a world that cannot be described in absolute ontological terms, like some hidden "complete set of properties", is unreal. Reality is whatever it is, we have no business telling that it can't be real unless it conforms to how we'd like to imagine it being. The same holds for 3-space vs. configuration space-- neither one is real, they are both ideas borrowed from mathematical structures for some good purpose.
 
Last edited:
  • #24
DevilsAvocado
Gold Member
751
91
The very idea that anything "manipulates particles" is already an unreal thing. "Manipulation" is an obvious anthroporphism, does the wind "manipulate" the sand? Does gravity "manipulate" the expansion of the universe? The logic is backward-- stuff happens, and the "manipulation" is in how we like to think about it. There's nothing wrong with thinking in those terms, we use words like "forces manipulate objects" all the time for good reasons, but we don't need to really believe it's true. It is easy to find interpretations of the very same physics that lack those elements, so they are clearly not endemic to the physics theory.
"The logic is backward-- stuff happens"

With this logic I can’t see how you could make use of any scientific theory. Science is about making models and predictions. If this is just reduced to:
– What happened dude!? :surprised

– I dunno, STUFF HAPPENS!! :yuck:

You got parody but not science.

This is exactly what I was complaining about in regard to the PBR theorem on a different thread-- the way they have tried to co-opt the term "real"!
It’s you who are promoting your "personal philosophical version of reality". Everyone else understands that we are talking about realism in relation to scientific Local Realism, as in relation to Bell's theorem, as in relation to the EPR paradox.

"THE ULTIMATE TRUTH" is matter for religion or philosophy to rant about.

Look at what you just said, you said that we should conclude the world is unreal if it is not governed by ontological hidden variables. Who ever said that a real world had to be so governed? I have no idea where that assumption comes from, there is nothing in any logically self-consistent definition of "real" that requires we dictate properties to it or else it can't be real.
I think you have to blame Einstein for "Real" or Hidden Variable Theories (HVT) or Counterfactual Definiteness (CFD).

You can talk and talk as much as you like, but Bell's theorem says:

No physical theory of local hidden variables can reproduce all of the predictions of quantum mechanics.

This means that Local Realism dead, which is also consensus within the scientific community.

As far as I know, there is no law forbidding us to find out if the world – AS EXPRESSED IN SCIENTIFIC TERMS – is non-local and/or non-real. My guess is that it will happen within 10 years.

Welcome to reality! :biggrin:
 
  • #25
Ken G
Gold Member
4,438
332
DevilsAvocado; said:
this logic I can’t see how you could make use of any scientific theory.
Well, maybe you are not following the logic.
Science is about making models and predictions.
I'd have to say that's pretty obvious. This is supposed to be news here?
If this is just reduced to:
– What happened dude!? :surprised

– I dunno, STUFF HAPPENS!! :yuck:

You got parody but not science.
No, what you have is poor logic. Apparently, your argument now rests on the syllogism that if we don't know why stuff happens, we cannot predict it? Let me introduce you to something you don't seem to know much about: it is called the history of science. Yes, the history of science, the story of predicting a whole bunch of stuff we didn't know why happened. It started with predicting the motions of planets, although we didn't know why they happened, and then a bunch of other stuff happened like that, which we figured out how to predict, but still didn't know why it happened. All good science. We didn't know why forces were associated with acceleration, yet we could predict it, we didn't know why masses generate gravity, yet we can predict it. We don't know what charge is or why electrons have it, or why superpositions are possible, or why there is a speed of light, yet we predict what will happen regarding charges, and superpositions, and the speed of light. The list is rather long, I guess you never realized that predicting stuff we don't know why happens is pretty much the definition of physics. Still, somehow you reduce all this to "if stuff just happens, there cannot be any science." Again, that would make sense if I didn't know the first thing about science.
It’s you who are promoting your "personal philosophical version of reality". Everyone else understands that we are talking about realism in relation to scientific Local Realism, as in relation to Bell's theorem, as in relation to the EPR paradox.
Wrong. We are talking about a realistic view of configuration space, or three-space, which are background milieu for dynamics-- nothing about local realism, which is a constraint on the types of dynamics that a theory can allow. I'm not making any claims about local realism, it's not even interesting since Bell. I'm saying that there is no point in trying to decide which is "more real", either configuration space or three space, because they both demonstrably exist "for real" in only one place-- the mathematical structures that define them. I can't think of anything more "realistic" than noticing this fact.
This means that Local Realism dead, which is also consensus within the scientific community.
You're the only one talking about local realism. I certainly am not-- I'm talking about the erroneous claim that "realism" implies that configuration space has to be more or less real than three-space. Actually, realism is a stance that our theories work because they have made some contact with what is real, but note that statement is not saying anything at all-- if we say that a theory being useful means that it connects with reality, and we define reality by whatever our useful theories connect with, then we have not said a thing about reality that is any different from noticing that our theories are useful. This is the problem with naive concepts of realism-- when the claims are weak enough to be logically internally consistent with how science works, they are not actually saying anything about reality at all. If you don't understand that, maybe someone else reading this will. It's time for the term "scientific realist" to mean something that actually makes sense with what science has always been, instead of a form of wishful thinking that requires ignoring essentially everyting that we know about the history of science.
 
Last edited:

Related Threads on The reality of Configuration space

  • Last Post
Replies
7
Views
8K
  • Last Post
3
Replies
70
Views
14K
  • Last Post
Replies
17
Views
1K
  • Last Post
Replies
3
Views
672
Replies
69
Views
14K
Replies
1
Views
1K
Replies
35
Views
1K
Replies
20
Views
6K
Replies
13
Views
3K
Replies
4
Views
898
Top