More evidence that the wavefunction is ontologically real?

[Quantumental]

This just in: http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3233.html

 

[arkajad]

The paper makes no sense at all as long as the concept of "measurement" is not precisely dynamically defined within quantum theory. These are just words with no precise meaning. Of course this what physicists do at the present time. Extraordinary claims need extraordinary proofs.

 

[jfizzix]

Apparently, if we say that reality is objectively defined, we can ask whether or not quantum states are objectively defined as well.

In particular, if the state of all information in reality pertaining to a quantum system is given by some set of variables \lambda, we can ask whether the quantum state |\psi\rangle is uniquely defined by \lambda.

It's a bit tricky, but what they try to show is that different states |\psi\rangle correspond to different (disjoint) sets of \lambda.

Since they appear to affirm this experimentally (within certain tolerances), it would mean that if one wants to consider the information encoding reality as objective, then one must also consider the quantum state of a system as objectively determined, and not something particular to the observer's state of knowledge.

Pretty awesome work, I must say!

 

[jfizzix]

I would need to go through the paper in more detail, but if I've read it correctly, this seems... profoundly significant.

 

[bhobba]

The paper makes no sense at all as long as the concept of "measurement" is not precisely dynamically defined within quantum theory

It is precisely defined - see for example section 2.5 of the following:
https://www.amazon.com/dp/3540357734/?tag=pfamazon01-20

Decoherence is a dynamic process.

Thanks
Bill

 

[bhobba]

Here is a free link:
http://arxiv.org/pdf/1412.6213v2.pdf

Note what it says:
'Assuming that some underlying reality exists, our results strengthen the view that the entire wavefunction should be real'

Its the same thing as the PBR theorem - its simply that if you assume some kind of reality in the first place, even in a weak sort of way, the wave function is in a stronger sense real. Interesting and likely quite important, but that assumption of reality, even in a weak sense, is precisely what many interpretations reject.

For example it doesn't apply to the ignorance ensemble interpretation - and quite a few others.

Thanks
Bill

 

[Nick666]

So let's assume the wave function is real. does that mean that qm needs no further interpretations? (consciousness, many worlds, etc)

 

[bhobba]

So let's assume the wave function is real. does that mean that qm needs no further interpretations? (consciousness, many worlds, etc)

No.

It changes none of the various interpretations where the wavefunction is real eg BM, MW, nelson stochastics, primary state diffusion etc.

Thanks
Bill

 

[bohm2]

One difference between this paper and PBR is that these authors do not rely on the assumption of preparation independence. They write:

Crucially, our theoretical derivation and conclusions do not require any assumptions beyond the ontological models framework, such as preparation independence, symmetry or continuity...

What is confusing (to me) is that the authors appear to argue that this assumption of preparation independence used by the PBR theorem is analogous to Bell's local causality. They write:

For example, Pusey et al. assume that independently-prepared systems have independent physical states. This requirement has been challenged as being analogous to Bell's local causality, which is already ruled out by Bell's theorem.

I still don't understand this. I didn't think that preparation independence and local causality are analogous? Regardless, the fact that one can narrow down the available "realistic" interpretations that are still viable is still progress.

 

[microsansfil]

Hello,

What is the meaning to be "ontologically real" in the framework of the physics ?

Patrick

 

[bohm2]

What is the meaning to be "ontologically real" in the framework of the physics ?

That the wave function is a mathematical entity/map that represents/refers to something that actually exists in the world, independently of any observer or agent.

 

[bhobba]

That the wave function is a mathematical entity/map that represents/refers to something that actually exists in the world, independently of any observer or agent.

The wavefunction is simply the representation of the state in the position basis. The state is the key thing.

To understand the issue see post 137 of the following:
https://www.physicsforums.com/threads/the-born-rule-in-many-worlds.763139/page-7

The state and its physical interpretation by the Born rule is in fact derivable from the operator formalism of QM - that's the import of Gleason's theorem the modern version of which the above link proved. This raises the question of is it real or simply something required by the math. Gleason's theorem suggests it's simply a mathematical requirement - but opinions vary.

Thanks
Bill

 

[TEFLing]

Wave functions are well described using complex numbers

Complex numbers are like a two part epoxy, having A and B components

Would the reality of the blobular blobulous wave function imply, that at some nano scoptic fempto scopic Planckoscoptic scale, that there actually is some two-component field, of which particles are storm like disturbances, which whirlwinds obey the SWE ?

 

[bhobba]

Would the reality of the blobular blobulous wave function imply, that at some nano scoptic fempto scopic Planckoscoptic scale, that there actually is some two-component field, of which particles are storm like disturbances, which whirlwinds obey the SWE ?

Sorry - but that's utter gibberish.

The reason we have complex numbers is the need for continuous transformations between pure states:
http://arxiv.org/pdf/quant-ph/0101012.pdf

Thanks
Bill

 

[TEFLing]

Sorry - but that's utter gibberish.

The reason we have complex numbers is the need for continuous transformations between pure states:
http://arxiv.org/pdf/quant-ph/0101012.pdf

Thanks
Bill

Why do complex numbers accurately model real experimental results?

If the wave function is real, and if a wave function is a complex valued field, then something corresponding to complex numbers would be real too, yes?

 

[bhobba]

Why do complex numbers accurately model real experimental results?

Why not? Exactly what limits the mathematical objects that can be used in physical models?

Here is the reason they are required in QM.

Suppose we have a system in 2 states represented by the vectors [0,1] and [1,0]. These states are called pure. These can be randomly presented for observation and you get the vector [p1, p2] where p1 and p2 give the probabilities of observing the pure state. Such states are called mixed. Probability theory is basically the theory of such mixed states. Now consider the matrix A that say after 1 second transforms one pure state to another with rows [0, 1] and [1, 0]. But what happens when A is applied for half a second. Well that would be a matrix U^2 = A. You can work this out and low and behold U is complex. Apply it to a pure state and you get a complex vector. This is something new. Its not a mixed state - but you are forced to it if you want continuous transformations between pure states.

QM is basically the theory that makes sense of such weird complex pure states (which are required to have continuous transformations between pure states) - it does so by means of the so called Born rule.

If the wave function is real, and if a wave function is a complex valued field, then something corresponding to complex numbers would be real too, yes?

You do realize that complex numbers are specified by two real numbers? If the wave-function is real then its specified by two real numbers. But that view isn't required to understand what's going on. QM is a mathematical model - any mathematical entity can appear in such models - complex numbers, Grassmann numbers, tensors - the list is endless.

The mathematical objects of a model aren't real - the reality lies in the correspondence rules of the model. For example show me a negative number of apples - but if you have borrowed some apples from a friend and need to return them that would be a reasonable model.

Thanks
Bill

 

[Ilja]

I think there is nothing problematic with giving the wave function the status of reality. Because there exists, anyway, some real values which correspond to it.

The wave function is always the result of a preparation procedure. And a preparation procedure is a measurement. We measure something, so the measurement result exists. Really, without any doubt really. And this measurement result, together with the history of the experiment itself, which has also happened really, is what defines the wave function.

In de Broglie-Bohm theory, this dependence is explicit. We have a wave function of the whole preparation procedure, \psi(q_{system},q_{device},t), and to obtain the effective wave function of the system, we need the trajetory of the measurement device: \psi(q_{system},t) = \psi(q_{system},q_{device}(t),t).

 

[bhobba]

I think there is nothing problematic with giving the wave function the status of reality.

Of course not.

There are many interpretations where its real.

Thanks
Bill

 

[ddd123]

Suppose we have a system in 2 states represented by the vectors [0,1] and [1,0]. These states are called pure. These can be randomly presented for observation and you get the vector [p1, p2] where p1 and p2 give the probabilities of observing the pure state. Such states are called mixed. Probability theory is basically the theory of such mixed states. Now consider the matrix A that say after 1 second transforms one pure state to another with rows [0, 1] and [1, 0]. But what happens when A is applied for half a second. Well that would be a matrix U^2 = A. You can work this out and low and behold U is complex. Apply it to a pure state and you get a complex vector. This is something new. Its not a mixed state - but you are forced to it if you want continuous transformations between pure states.

Whoa, finally an explanation that I can understand. I kept reading this thing in the usually linked arxiv articles and not getting it. Are there any lectures or books you can suggest that explain C*-algebras for QM to non-mathematicians? I mean physicists trained in a standard way, no math gibberish (or yes, but explained from scratch).

 

[bhobba]

Are there any lectures or books you can suggest that explain C*-algebras for QM to non-mathematicians?

No - its very hard even for trained mathematicians. Its an extremely mathematically advanced formulation of QM.

Thanks
Bill

 

[Quantumental]

I think there is nothing problematic with giving the wave function the status of reality. Because there exists, anyway, some real values which correspond to it.

[...]

In de Broglie-Bohm theory, this dependence is explicit

But in Bohm, given the ontological nature of the WF it's hard to see how you avoid infinite Many Worlds with 1 special particle world.

 

[Ilja]

But in Bohm, given the ontological nature of the WF it's hard to see how you avoid infinite Many Worlds with 1 special particle world.

Sorry, but for me it is extremely difficult to see how one can obtain infinite many worlds out of a function defined on imaginable worlds.

Say, a function on all imaginable worlds can easily exist in my mind - as a collection about ideas about all such worlds. My mind really exists. Thus, the ideas about all these worlds also exists. But all these other worlds do not exist. Even if this example may be slightly artificial, but the conceptual problem that a function on some space of objects can easily exist without the objects

Of course not.
There are many interpretations where its real.

Ok, let's make the statement a little bit more nontrivial: It is not even a problem for an epistemic interpretation. Because one has to distinguish the epistemic interpretation of the wave function of the universe from the interpretation of the wave function of the particular subsystem.

The wave function of the whole system, which prepares the particular system, is in itself not prepared - this would give an infinite regress. Thus, what we know about it? Nothing. And it is this nothingness which suggests that this unprepared wave function is epistemic. But, when, we compute the effective wave function of the subsystem, by using some element of reality - the trajectory of the measurement device. Thus, the effective wave function of the subsystem depends on elements of reality. Thus, it is not purely epistemic, but at least partially ontic.

 

[julcab12]

.. It just happened that we have 2 measured/observed realities and each can be expressed in variety of ways. Some my favor that wavefunction behavior as a first order. Hence, the fundamental reality. But we really don't know except that we can see things to be this way. Nature is pretty deceiving; bizarre and it's not always what it seems or look like based on macro world idealization and i find QM to be very direct. http://physics.stackexchange.com/questions/154431/are-wave-functions-real-physical-objects

 

[zonde]

I think there is nothing problematic with giving the wave function the status of reality.

But there are conjugate variables. Remember EPR paradox?

Because there exists, anyway, some real values which correspond to it.

There are only probabilities. Probabilities are not real.

 

[julcab12]

There are only probabilities. Probabilities are not real.

Maybe in a classical continuous view but we don't have or can't proved that.. In general QM sense. The x always goes to infinite, states of which each is independent to one another -- individual states.

 

[Feeble Wonk]

It seems to me that I have, in the past, been professorially chastised for questioning what quantum physics implies about "reality" at the fundamental level, as well as when I suggested that it seems in many ways that the only thing "real" about the quantum state of a physical system is the information that describes it. Despite that, it appears that this thread demands that those issues to be addressed.

First off, what does it mean for something to be "ontologically real"? The definition of "ontological" (according to i.word.com) is :"relating to or based upon being or existence." I interpret that to mean that it's something that actually "exists", in a substantive manner.

I think there is nothing problematic with giving the wave function the status of reality. Because there exists, anyway, some real values which correspond to it.

But, to what do the values correspond? What is it that actually "exists" that the values describe?

...the wave function is a mathematical entity/map that represents/refers to something that actually exists in the world, independently of any observer or agent.

The mathematical objects of a model aren't real - the reality lies in the correspondence rules of the model. For example show me a negative number of apples - but if you have borrowed some apples from a friend and need to return them that would be a reasonable model.

Yet, negative numbers don't actually "exist", in a substantive manner. For that matter, neither do positive numbers, nor arithmetic functions. They are mathematical constructs... abstract ideas. They have no substantive form.

Apparently, if we say that reality is objectively defined, we can ask whether or not quantum states are objectively defined as well.
...
Since they appear to affirm this experimentally (within certain tolerances), it would mean that if one wants to consider the information encoding reality as objective, then one must also consider the quantum state of a system as objectively determined, and not something particular to the observer's state of knowledge.

So, this leaves me with the question... Is the information content of the quantum state what is objectively "real". Is it, in fact, all that is "real"?

 

[LQY]

Measurements can only detect eigenvalue, so any problems beyond eigenvalue of the wavefunction is hard to answer. If wavefunction is ontologically real or not is one of such questions.

 

[ephen wilb]

In the double slit experiment, the detector collapse the wave function in Copenhagen. If it doesn't collapse, then it automatically forms Many Worlds? or does the wave function simply vanish or no effect on this world (if no collapse occurs just for sake of discussions)?

 

[bhobba]

The wave function of the whole system, which prepares the particular system, is in itself not prepared - this would give an infinite regress. Thus, what we know about it? Nothing. And it is this nothingness which suggests that this unprepared wave function is epistemic. But, when, we compute the effective wave function of the subsystem, by using some element of reality - the trajectory of the measurement device. Thus, the effective wave function of the subsystem depends on elements of reality. Thus, it is not purely epistemic, but at least partially ontic.

Sorry - but I don't get that at all eg why even the concept of 'prepared' is applicable to wave-function needs detailing before you can even introduce it in that context. In modern times state and preparation procedure are pretty much synonymous but that requires detailing of what it is in the first place - which is very interpretation dependant. To me it looks like typical philosophical 'waffle' that basically makes my eyes roll back and I want to switch off. Philosophically its what Wittgenstein said: 'Whereof one cannot speak, thereof one must be silent'

We have all sorts of interpretations where the state (I dislike wavefunction because that gives the position basis a privileged role) has all sorts of statuses. The fact they are valid interpretations means you can't say, a priori, anything about the status of the state. Arguments like the above must have a flaw - but since I don't even understand it what that is beats me.

Thanks
Bill

 

[bhobba]

But in Bohm, given the ontological nature of the WF it's hard to see how you avoid infinite Many Worlds with 1 special particle world.

You are mixing concepts from interpretations as if they were the same interpretation. That is, and very obviously so, flawed logic.

Thanks
Bill

 

[bhobba]

.. It just happened that we have 2 measured/observed realities

2 measured/observed realities? I have zero I idea where you are getting stuff like that from, or even what it means, but in physics, and science in general, we try to be concise and not obscure.

Thanks
Bill

 

[bhobba]

So, this leaves me with the question... Is the information content of the quantum state what is objectively "real". Is it, in fact, all that is "real"?

Its interpretation dependant - the formalism is silent on the issue of the reality of a quantum state.

Formally QM is a generalised probability model - in fact the simplest that allows continuous transformations between pure states. States are a generalisation of probability. Is the probability you assign to the face of a coin real? Philosophers argue about that sort of thing all the time and get nowhere. In physics we simply accept the theory is silent on the issue with different interpretations having different views - well most do anyway - some want to go down the philosophy path - but that is not what this forum is about.

Thanks
Bill

 

[bhobba]

In the double slit experiment, the detector collapse the wave function in Copenhagen. If it doesn't collapse, then it automatically forms Many Worlds?

No. There are many interpretations of QM besides Copenhagen and MW - some have collapse, some don't, some have many worlds, some even have many minds, there are all sorts out there.

Thanks
Bill

 

[Swamp Thing]

Whoa, finally an explanation that I can understand.

Me, too! And if I can understand something, it means you can't make it much simpler or clearer, believe me. I have been walking on air since I read those paragraphs. Thanks, bhobba !

 

[julcab12]

2 measured/observed realities? I have zero I idea where you are getting stuff like that from, or even what it means, but in physics, and science in general, we try to be concise and not obscure.

Thanks
Bill

Microworld is very different in approaches from the macroworld. Quantum nonlocality disappears as things get bigger. My monitor doesn't appear to be in places at the same time or jittery. It looks different to me?

 

[bhobba]

Microworld is very different in approaches from the macroworld. Quantum nonlocality disappears as things get bigger. My monitor doesn't appear to be in places at the same time or jittery. It looks different to me?

That's exactly my issue. QM says none of those things - it is silent on it. If QM is non-local or not is interpretation dependant - the same with things being in two places at once (although I don't know any interpretations that says that - but there may be some).

Thanks
Bill

 

[Quantumental]

You are mixing concepts from interpretations as if they were the same interpretation. That is, and very obviously so, flawed logic.

No. If you want an ontological wavefunction and you accept functionalism you do not get to say that by magic the worlds do not occur in the wavefunction

 

[bhobba]

No. If you want an ontological wavefunction and you accept functionalism you do not get to say that by magic the worlds do not occur in the wavefunction

You logic is flawed. BM is an ontological interpretation that does not involve worlds - QED - your argument is wrong.

Thanks
Bill

 

[Quantumental]

You logic is flawed. BM is an ontological interpretation that does not involve worlds - QED - your argument is wrong.

Thanks
Bill

This is what happens when otherwise very smart people decide to ignore philosophy. Saying that the worlds aren't in the wavefunction doesn't actually remove them. As has been argued in the litterature before: http://philsci-archive.pitt.edu/1659/1/Cushing.pdf

 

[julcab12]

That's exactly my issue. QM says none of those things - it is silent on it. If QM is non-local or not is interpretation dependant - the same with things being in two places at once .

Thanks
Bill

... I'm just saying it is different by behavior but not solely disconnected(post#23). If your saying that QM is only constrained to a certain formalism -- certain formalism or statistic or probabilty simply because things doesn't behave or obey at what we usually expect (classical). What about quantum observables or observed quantities.. Are observed behavior interpretation dependent too? If say, when particle are observed to be in multiple places at the same time. QM is out of the picture? I'm confused.

 

[ephen wilb]

No. There are many interpretations of QM besides Copenhagen and MW - some have collapse, some don't, some have many worlds, some even have many minds, there are all sorts out there.

Thanks
Bill

Ensembles or Copenhagen smell of Newtonians.. because in Newtonian classical world is the primary.. and you treat the wave functions as just ensembles or subjective or just probabilistic tools in a primary Newtonian world... with definite outcome as the primitive of the axiom. But isn't this Newtonian biased? You know Newtonians are just illusions. Newtonians is just smoke and mirrors.. so is not ensembles interpretation going backwards (in thinking)?

 

[bhobba]

But isn't this Newtonian biased?

Its got nothing to do with Newtonian mechanics. I have zero idea how you would form such a view. Its simply an interpretation of probability - frequentest vs bayesian:
http://jakevdp.github.io/blog/2014/03/11/frequentism-and-bayesianism-a-practical-intro/

The ensemble interpretation is frequentest in that it views the possible outcomes of an observation as a large ensemble determined by the state and observation. Copenhagen is Bayesian in that it views the state as subjective knowledge.

Unfortunately Copenhagen sometimes isn't explained well - the following fixes that:
http://motls.blogspot.com.au/2011/05/copenhagen-interpretation-of-quantum.html

Thanks
Bill

 

[carllooper]

Microworld is very different in approaches from the macroworld. Quantum nonlocality disappears as things get bigger. My monitor doesn't appear to be in places at the same time or jittery. It looks different to me?

Non-locality isn't quite the same thing as superposition. And neither disappear at macro-scales. A particle in so-called super-position can occupy a wave that is miles across. The EPR mind experiment involved galactic distances.

The non-local refers to relationships between things or events, and measurable ones as much as any unmeasurable ones. For example, the concept of distance (a measurable attribute) is one of the simplest measurable conceptions of the non-local. The distance between a couple of apples sitting on a table is not localised in anyone of the apples. The distance between the apples represents a relationship between the apples rather than anything specific to the apples themselves. In this case the relationship is a spatial relationship. And if we were to move one of the apples, while not touching the other apple, this spatial relationship (ie. the distance between the apples) would change. And this change in distance would demonstrate that a local change (moving one of the apples) altered a non-local attribute (the distance between them). Or equally: that altering the distance between them, altered one or both of the apples!

Understood in this way, non-locality isn't that strange, nor new. However it's had a very troubled history due to it's early association with the supernatural.

C

 

[ephen wilb]

Its got nothing to do with Newtonian mechanics. I have zero idea how you would form such a view. Its simply an interpretation of probability - frequentest vs bayesian:
http://jakevdp.github.io/blog/2014/03/11/frequentism-and-bayesianism-a-practical-intro/

The ensemble interpretation is frequentest in that it views the possible outcomes of an observation as a large ensemble determined by the state and observation. Copenhagen is Bayesian in that it views the state as subjective knowledge.

Unfortunately Copenhagen sometimes isn't explained well - the following fixes that:
http://motls.blogspot.com.au/2011/05/copenhagen-interpretation-of-quantum.html

Thanks
Bill

When one mentions "Newtonian".. it is automatically "Newtonian mechanics"? I was thinking Newtonian refers to nuts and bolts and macroscopic classicality. Special relativity and quantum mechanics are supposed to be saying things are not what they seem. Newtonian mechanics being just classical limits and coarse grain limit of a universe where things were supposed to expand, dilate in SR and vanish and in two places at once in QM. In your view. SR and QM are just for calculations and not really objectively there creating matter, space and time?

 

[carllooper]

Ensembles or Copenhagen smell of Newtonians.. because in Newtonian classical world is the primary.. and you treat the wave functions as just ensembles or subjective or just probabilistic tools in a primary Newtonian world... with definite outcome as the primitive of the axiom. But isn't this Newtonian biased? You know Newtonians are just illusions. Newtonians is just smoke and mirrors.. so is not ensembles interpretation going backwards (in thinking)?

Ensemble theory isn't necessarily Newtonian, although there are Newtonian (or classical) conceptions of the ensemble. If you were to treat the ensemble as a function of otherwise independent effects (or causes) then you might be entertaining a classical version of such theory. But in an alternative version of such, (and not necessarily modern for that matter) the collective operation (the ensemble) of otherwise individual effects (or causes) can be treated as the fundamental "reality" being studied. The events as individual and independant of each other become the "illusion" (so called).

But these terms "reality and "illusion" are just historically loaded terms. It doesn't really matter which is called which, or what you study. The so-called "illusions" are just as interesting, from the point of view of science, as the so-called "realities".

C

 

[bhobba]

and in two places at once in QM.

QM doesn't say that.

In your view. SR and QM are just for calculations and not really objectively there creating matter, space and time?

That depends on what you mean by objectively there. I consider 'objectively there' to be what out theories describe, so obviously its 'objectively there' in my view. However philosophers argue incessantly what things like that mean, and never reach any conclusion, so my view won't resolve anything.

Thanks
Bill

 

[carllooper]

It seems to me that I have, in the past, been professorially chastised for questioning what quantum physics implies about "reality" at the fundamental level, as well as when I suggested that it seems in many ways that the only thing "real" about the quantum state of a physical system is the information that describes it. Despite that, it appears that this thread demands that those issues to be addressed.

First off, what does it mean for something to be "ontologically real"? The definition of "ontological" (according to i.word.com) is :"relating to or based upon being or existence." I interpret that to mean that it's something that actually "exists", in a substantive manner.

But, to what do the values correspond? What is it that actually "exists" that the values describe?

Yet, negative numbers don't actually "exist", in a substantive manner. For that matter, neither do positive numbers, nor arithmetic functions. They are mathematical constructs... abstract ideas. They have no substantive form.

So, this leaves me with the question... Is the information content of the quantum state what is objectively "real". Is it, in fact, all that is "real"?

A mathematical model represents what otherwise "exists". To the extent that there are things that exist, which can be represented with a negative number, one will use such numbers to represent such things. Bhobba's example of a debt is just such an example. If one regards a debt as real (ie. that you are not a thief and intend to pay back the debt) then you can represent this debt (in your ledger) with a negative number.

Although a mathematical model represents something other than itself that doesn't mean it's not in itself a "reality". Indeed I imagine most mathematicians would treat mathematics as a "reality" in itself. But in the context of physics a mathematical model (also) represents something other than just itself. It refers us back to, at the very least, some observable phenomena: the results of an experiment (or just fortuitous observations). But models tend to go a bit further than just what is observable. After all, if it's only the observations one is interested in then one can just do the experiments and not trouble oneself with any models.

A model tends to treat the observations (ie. the results of experiments) as a function of something more "real" behind such observations. One speaks of the "reality" behind an observation. One models this "reality". Now a model will produce it's own results, and any agreement between the model's results, and otherwise experimental results will typically be treated as a good thing. What one is after. The model is effectively a substitute for what is otherwise not immediately obvious in an experimental observation - be it the notion of some invisible "reality" behind such observations, or simply some unobvious pattern (or signal) in the observations itself: drawing our attention back to the observation and what we might have overlooked but is otherwise entirely visible in the observation.

The question of "reality" will always be a vexed one because most conceptions of such treat it as being something different to what is observable - as that which is "behind" the observable, rather than equal to it. An invisible reality. As if what we observe was some sort of illusion, or was subjective. At best a representation. As if observations were in themselves something not real. As if we were all living in The Matrix, or Plato's cave. Its a particularly ancient idea but also a very compelling one. But how does one emperically prove this concept of reality (of that which would be outside of the cave)? By definition one can't. It's invisible! As troubling as this notion of "reality" is (as something invisible and fundamentally different from observation) it has nevertheless proved a very useful concept. However it is still just another model.

The simplest approach, I find, is to treat that which is observable, as one's starting concept of reality. Whenever you run into trouble with a model, you just return to this reality (rather than the idea of some reality behind such). There is something extremely simple about this approach. Myself I find it even easier to treat observations, not only as a starting reality (and a reality to which one might return when in trouble) but as the only reality there is: that there is no reality behind an observation - that observations themselves are the fundamental reality about which we are otherwise creating models. The models become a way of expressing, in more formal terms, what would otherwise be visible (or can be made visible) - rather than expressing the invisible.

C

 

[Nick666]

carllooper , I opened a thread in General Discussion, if you want we can continue there .

 

[Feeble Wonk]

I hope my post (#26) didn't drop us into the philosophical abyss. I'm sincerely attempting to comply with the PF convention to refrain from that. But, again, this subject matter by its very nature requires that we at least tread carefully toward the slippery slope without sliding over the precipice.

A mathematical model represents what otherwise "exists".
...
Although a mathematical model represents something other than itself that doesn't mean it's not in itself a "reality".
...
The question of "reality" will always be a vexed one...

C

As Carl suggests, any reference to an ethereal and/or abstract reality is "vexing", because that concept of "reality" allows for a confounding degree of ambiguity. Yet, the ONTOLOGICAL designation should alleviate a great deal of that ambiguity. In an effort to get back on topic, and make my point more clearly, I'd like to return to the money analogy for just a moment. What the concept of money "represents", in terms of its relative value, might be "real" in some respects, but it is not ontologically real. The aspect of money that is ontologically real is the paper of the currency, and the metal of the coin. Ontological reality is tangible and substantive. It is what it is, not what it represents.

Its interpretation dependant - the formalism is silent on the issue of the reality of a quantum state.

Formally QM is a generalised probability model - in fact the simplest that allows continuous transformations between pure states. States are a generalisation of probability. Is the probability you assign to the face of a coin real?

I suppose this is precisely the issue that I'm trying to clarify. Regardless of the QT interpretation, as Bill reminds us, the wave function itself is a "probability model". It's not a "thing", in the sense that you can hold it in your hand. And, it doesn't represent the observable. It represents the "probability" of how you will observe the observable when you look. It is, by its very nature, information, and only information. I don't understand how this mathematical entity can be, or represent, something that is "ontologically" real.

Here is a free link:
http://arxiv.org/pdf/1412.6213v2.pdf

Note what it says:
'Assuming that some underlying reality exists, our results strengthen the view that the entire wavefunction should be real'

So, if this paper is claiming that it has demonstrated that the wave function is as equally "real" as is the "pure" quantum state of a physical system... as "real" as any underlying reality that exists... is it arguing that "reality" in general is fundamentally informational?

 

[carllooper]

There's nothing to suggest that what is observable isn't also that which some position (such as mine) would mean by "ontologically real".

An observation is both tangible and substantive.

And if not why not?

If by the phrase "ontologically real" one means something other than an observation, then one is left with either the model (a representation) and/or some non-observable reality (represented by the model).

Neither of which seem to me to be any more tangible and substantive than an observation. But on the other hand no less tangible and substantive.

A non-observable reality needs some way of being expressed in terms that do not depend on observation - for obvious reasons. A model is precisely the means by which such a reality can be expressed. For that reason such a model, and what it represents, are 'entangled' with each other. They become, in a sense, the 'same' thing. An observable reality doesn't depend on a model in quite the same way since the reality being established is already expressed by a given observation.

A model, as mentioned, seeks to go beyond what is simply given as raw data. The concept of raw data invokes for example, a list of numbers. For obvious reasons a list of numbers can look pretty meaningless and offer not much insight into what one might be wanting to do with such numbers. And so models are made to sort of put all these numbers into some sort of more manageable form. And by assuming there is some sort of more ordered "reality" producing these numbers in the first place, really effective models have been made. There's no denying this. Models are really really effective things.

Whether we call them real, or a representation, or ontologically real, or not ontologically real, or merely "adequate" as Bohr once said is really beside the point. Who cares? Who cares are those who need the models rather than the philosophical trajectories that such models might invoke or contest. They need the models in the work they do - be it to manage raw data or design some new technology. There are all sorts of reasons.

For example, I'm currently building an optical printer for 16mm and Super8 film. I need a model of light transmission in terms that will allow the computer control system to dynamically adjust the exposure time as a function of dynamic changes in magnification. I don't necessarily need the full quantum mechanical picture for this, but it doesn't hurt factoring such in since it can then handle some of the more subtle operations the system might be expected to handle - to do with holographic encodings. What matters in this context is not whether the models correctly represent some notion of an ontological reality but that the model gives the correct value to set the exposure time (amongst other things) - which one assumes it would do if the model represented reality - but needn't do so - as long as the result is effectively the same.

Be that as it may, the philosophical trajectory is still interesting. One is in a sense always doing philosophy anyway. Model makers use philosophy all the time - not classical philosophy, but versions thereof - adapted to the problems at hand and the way nature expresses herself, rather than some fantasy of complete "philosophical" closure on the nature of the universe.

The concept of reality as fundamentally information is, I think, quite a good one. I've found it a productive angle to take.

C