Not in physics. In physics a wave is a phenomenon that behaves in accordance with the wave equation. — andrewk

No, in my high school physics, that is not how "wave" was defined. Here is what Wikipedia says:

"In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport (Mass transfer). Waves consist of oscillations or vibrations of a physical medium or a field, around relatively fixed locations."

Notice two key points: first, "transfers energy", second, "vibrations of a physical medium or field". The problem with "vibrations of a field", is that a "field" is purely mathematical, there has been no physical substance identified which corresponds to "field". Nothing corresponds to "field", it is pure mathematics, so it is nonsense to talk of vibrations of a field. And waves as "vibrations of a field" is something completely imaginary.

Another thing, in relation to the Michelson-Morley experiment. That experiment was completely inadequate because it premised a separation between physical objects and the supposed medium. It did not account for the possibility that objects are part of the medium, that the objects and the space between them are all part of the same medium. And, the empirical evidence, that light waves pass through physical objects, indicates that the objects must be part of the medium.

don't think physics provides any reason to doubt that the elementary particles (as described in the Standard Model) exist and have measurable physical properties just as everyday macroscopic objects do. — Andrew M

I don't agree with this. I've spoken to physicists who say that there is no reason to believe that what they call "particles" in the Standard Model, are actually particles at all. That's just the word that is used. Of course there is something real here which is referred to by the word, but what the word is actually refers to is states of the field. However, the "field" is purely mathematical, with nothing physical corresponding. Therefore it is incorrect to say that these particles actually exist, they are products of the mathematics.

The issue here is that a "field" is an imaginary thing, created by mathematics.

Could you explain what a Higgs field is?

In your reply you seek first to counter my suggested definition of 'wave' by referring to the definition currently on Wikipedia - which anybody could change in two minutes - and then at the end of your third para to claim that part of the Wikipedia definition is nonsense.

The problem is that you come from an entrenched Aristotelian position that rests on an axiom that everything is 'substance'. As a remedy, I recommend a reading of Nagarjuna, who argues persuasively that there cannot be any such thing as substance.

Or you could listen to Alan Watts about the Prickles and the Goo views of the world,

To complicate matters, the 'wave function' is, I believe, a misnomer. It's not a 'wave' in the way waves are understood either in physics or in everyday discussion. — andrewk

Right. That's why I said it wasn't 'a kind of phenomena'. (Incidentally check this thread out).)

what does it mean for a physical system to be in a superposition of states given that it will always be measured in a definite state? — Andrew M

That's the interpretive problem in a nutshell.

don't think physics provides any reason to doubt that the elementary particles (as described in the Standard Model) exist and have measurable physical properties just as everyday macroscopic objects do.
— Andrew M

I don't agree with this. I've spoken to physicists who say that there is no reason to believe that what they call "particles" in the Standard Model, are actually particles at all. That's just the word that is used. — Metaphysician Undercover

That's like saying that what we call "apples" aren't actually apples, that's just the word we use. So it's really a semantic issue. If one understands particles in a classical sense (i.e., as having an absolute state) then, I agree, physics gives us no reason to think such things exist. However if one understands particles (and apples) in a quantum/relativistic sense (as having a relative or relational state) then there is no problem - it's a natural fit.

The issue here is that a "field" is an imaginary thing, created by mathematics. — Metaphysician Undercover

Or, conversely, it's not imaginary since it has physical consequences. Perhaps consider it a manifestation of the measurement problem that can be understood in terms of potentiality.

Could you explain what a Higgs field is? — frank

I'm not familiar enough with QFT to do so. But here is someone else's explanation that I found helpful.

That's the interpretive problem in a nutshell. — Wayfarer

:up:

Apologies for slow reply time.

I believe that if you say that something 'not real' describes 'a real thing' you're just re-asserting a realist/representational view. The 'unreal'/'non-representational' view of the wave-function advocated by Rovelli, Bitbol etc is that the wave-function does not describe anything. It is just a tool. — boundless

A tool (a map of Paris say) may be just a tool and not be the thing it describes, but it very much still describes Paris. Thus I object to the statement that the tool doesn't describe anything.
I guess I'm not much in that camp since I personally suspect the wave function isn't just a tool.

This is very compatible with the view that collapse is due to an increase of knowledge (i.e. an 'epistemic', not 'ontic' view).

I would not call what a table lamp does 'epistemic', so again, I do not personal hold view described there.

In other words, 'real' and 'representational' should be taken as synonyms (or very close to that) - the point is that there is a biunivocal correspondence between mathematical formalism and reality.

Disturbingly close, yes, to the point where no arbitrarily close inspection will yield a difference. This is not true of the paper map of Paris.

The point in bringing this distinction between two different 'sub-interpretations' of dBB was simply to explain better what I mean by 'real'. If you think that the wave-function has some ontological meaning, then the wave-function is real/representational. If not, it is just a tool of some sorts.

I don't think there is just the two choices. It is certainly not representational in my opinion, but the wave function has meaning only in relations, not objectively, so it isn't ontological as in 'is real' but more like 'does relate to'. 5 really is less than 7 and that is not just a representational property of the tool that is the integers, and yet the integers don't need to have Platonic realism (ontological meaning) for that relation to be true.

In your reply you seek first to counter my suggested definition of 'wave' by referring to the definition currently on Wikipedia - which anybody could change in two minutes - and then at the end of your third para to claim that part of the Wikipedia definition is nonsense. — andrewk

The point remains, that in physics a wave is defined as a vibration in a medium. It is an activity, and when there is activity there is something which is active. We can have a verbal, or mathematical description of a type of activity and that description can stand alone, as activity X, but once we apply the description to something real (use it to describe something), we engage with the underlying assumption that there is something which is involved in that activity. If it helps for you to understand this by referring to Aristotelean "substance", that's fine, but it's just a simple fact about how we describe things. If we describe a movement in the world it is assumed that there is something moving, otherwise we are describing a type of motion, a concept.

I admit that I was wrong to say that a field is completely mathematical, physicists do regard fields (like an electromagnetic field) as real things. The problem is that a field is modeled as force, and therefore potential energy. So the real existence of the field is modeled as the potential for activity in an object. For example, you can map a space with coordinates and show with vectors the force at each point. The force will change as time passes, and this may display a wave-like pattern.

The issue is that this is not the modelling of a wave. It is the modelling of a wave-like force. It is not the activity of a wave which is being modeled, what is being modeled is a force which has the capacity to cause activity in objects. As an analogy, suppose we model the force of a hammer hitting a nail. We model the effects of the hammer on the nail. This is not a modelling of the hammer. Looking at the model of this force, without any other information, we would assume that there is something there (substance, the hammer itself), which hits the nail. But we have no information about that thing other than the force which it applies on the nail, so we have no means for describing that thing itself, until we look directly at it as a thing to observe. Likewise with the modeling of the force within a field. What is modeled is the effects of the force on objects. This indicates a wave-like activity. But until we look at the field itself, as an object, a moving thing (and this means as a wave in a medium), therefore something actually moving rather than the potential for motion, we have no means for properly understanding that thing.

That's like saying that what we call "apples" aren't actually apples, that's just the word we use. So it's really a semantic issue. If one understands particles in a classical sense (i.e., as having an absolute state) then, I agree, physics gives us no reason to think such things exist. However if one understands particles (and apples) in a quantum/relativistic sense (as having a relative or relational state) then there is no problem - it's a natural fit. — Andrew M

Well, I wouldn't agree that "there is no problem". Let's assume two distinct ways of using "particle". Now we must avoid equivocation so we need some principles to distinguish between particles in the classical sense and particles in the quantum sense. If we start looking at different particles, when do we cross that line? Take an electron for example. It must be a particle in the classical sense, because the structure of molecules and atoms is dependent on those particles. However, it also appears to be a particle in the quantum sense. And this might appear to be the case for the other parts of an atom. We can't use "particle" in both senses without equivocating, and we cannot say that these parts of the atom are actually both types of "particle", because that would be contradictory.

Or, conversely, it's not imaginary since it has physical consequences. Perhaps consider it a manifestation of the measurement problem that can be understood in terms of potentiality. — Andrew M

OK, so as I explained above to andrewk, I'll accept that a field is assumed to be more than imaginary. The problem is that it is modeled as the potential for activity, rather than a real active thing. So the issue is with the modeling technique, not the assumption that an imaginary thing is real. Therefore there is an inconsistency between the assumption, that the field is a real active thing, and the modeling of the field, as the potential for activity.

I'm not familiar enough with QFT to do so. But here is someone else's explanation that I found helpful. — Andrew M

Very helpful. Thanks!

The point remains, that in physics a wave is defined as a vibration in a medium. — Metaphysician Undercover

No, It doesn't, and it isn't.

Would it have been, pre-Schrodinger?

EM waves don't have a propagation medium either.

RIght. I guess that went out along with ether, didn’t it.

Think that's how it happened. Michaelson-Moorley? Michaelson-Morley, was linked by andrewk earlier in response to MU IIRC.

Apologies for slow reply time. — noAxioms

No worries!

A tool (a map of Paris say) may be just a tool and not be the thing it describes, but it very much still describes Paris. Thus I object to the statement that the tool doesn't describe anything. — noAxioms

I see what you mean and IMO this is a good argument against a 'non-representional' reading of the wave-function: it is difficult to accept that the wave-function can have absolutely no ontological meaning and, at the same time, be so useful.

I actually am not sure. On one hand, I am inclined to say that when the 'observation' occurs the other 'branches' do not exist (for the 'observer'). On the other hand, I recognize that the 'non-representational' reading is problematic. Maybe thinking in terms of potentiality/actuality helps.

This is very compatible with the view that collapse is due to an increase of knowledge (i.e. an 'epistemic', not 'ontic' view). — boundless

I would not call what a table lamp does 'epistemic', so again, I do not personal hold view described there. — noAxioms

Ok, I agree. Bad choice of terms on my part. For the sake of generality, let's just say 'not ontic' instead of 'epistemic' and drop using the word 'knowledge' in favor of 'addition of new 'information'' (for the lack of a better term).

In other words, 'real' and 'representational' should be taken as synonyms (or very close to that) - the point is that there is a biunivocal correspondence between mathematical formalism and reality. — boundless

Disturbingly close, yes, to the point where no arbitrarily close inspection will yield a difference. This is not true of the paper map of Paris. — noAxioms

Again, you are right! I should have said, instead: 'non-representational' means that the wave-function simply does not have any ontological meaning.

I don't think there is just the two choices. It is certainly not representational in my opinion, but the wave function has meaning only in relations, not objectively, so it isn't ontological as in 'is real' but more like 'does relate to'. 5 really is less than 7 and that is not just a representational property of the tool that is the integers, and yet the integers don't need to have Platonic realism (ontological meaning) for that relation to be true. — noAxioms

Ok, I see. I am open to the view that there is a 'middle way' between the two positions. At the same time, however, I am not sure if what you are describing here can be applied to the 'version' of RQM that I have in mind where after the observation, for the observer, the other branches do not exist.

BTW, I am sympathetic to some kind of realism for mathematics. I do not believe that mathematics is entirely a product of our minds but, at the same time, the usual version of mathematical Platonism does not convince me. So, maybe mathematical relations are 'real' (but not 'physical'). Interesting view :smile:

In my opinion Wheeler's view is a bit ambiguous. At times he suggests some form of 'panpsychism'. In other places, he seems to suggest that an 'observer' can be a sufficiently complex physical object. By 'sufficient complex physical object', I mean that such an object must be able to store and process information. And maybe, he considers that these objects are somehow sentient.
But IMO, he does not give a 'special role' to human consciousness (or animal consciousness...).

Personally, I prefer either Bitbol's approach, where you can define perspectives to sentient beings, or Rovelli's approach where you can define a perspective to everything (and might relate Rovelli's view to a form of panpsychism). — boundless

I'll now explain why I believe that replacing 'conscious observers' with 'sufficiently complex physical object/system' does not solve anything IMO.

In CI, 'classicality', i.e. having definite values of physical quantities, arises due to collapse of the wave-function. But collapse itself needs in CI a classical physical system, i.e., in this view, a 'sufficiently complex physical system'.

This is a deep issue in CI. Classicality is both a pre-condition to explain 'measurements' and a consequence of measurement. So, the problem of conscious observers is now replaced by another problem: CI cannot explain the arising of classicality - after all, to work CI requires that something must be treated as classical in the first place. Hence, the first occurrence of a 'classical system' is left completely unexplained in CI. Hence as it is said in in an already quoted article by Bitbol (http://www.bourbaphy.fr/bitbol.pdf), according to CI:

As a well-known article about the measurement problem of quantum mechanics puts it: the quantum theory can describe anything, but not everything [Peres1982][Fuchs2000].

This also shows IMO that the problem of the validity of 'ancestral statements' is not solved by replacing 'conscious observers' with 'sufficiently complex physical systems'. CI needs some kind of classical object as a starting point.

If one wants to avoid completely the problems due to giving a special role to conscious observers of some physical systems, one IMO should simply choose another interpretation. After all, there are a lot of interpretations of QM. RQM for instance does not have this problem because it treats all physical systems as 'observers', so there is no problem to explain how 'classicality' arises.

EM waves don't have a propagation medium either. — fdrake

That's what I've been discussing with andrewk, whether EM waves are real waves or not. Andrewk insists that "wave" is defined in physics in such a way that a medium is not required for a wave. But this is contrary to the Wikipedia page on waves in physics, and contrary to what I learned in high school physics, as well. I think andrewk is just fabricating a definition to support an ontological position, and asserting the correctness of that intentionally directed definition.

Think that's how it happened. Michaelson-Moorley? Michaelson-Morley, was linked by andrewk earlier in response to MU IIRC. — fdrake

As I explained to andrewk, the Michelson-Morley experiment was inadequate, using the restrictive premise that objects would be separate from the ether rather than a part of it. That premise is contrary to observational evidence that EM waves penetrate objects. The premise that an object, such as the earth, is independent from the ether is misleading. This is evident in QM, which models the object (particle) as a property of the wave field.

Here's the conclusion from your referenced Wikipedia page. Notice that the experiments were inconclusive. Al that such experiments really show is that the relationship between the proposed ether and the earth, is unknown. Instead of resolving the issue, of the relationship between the ether and physical objects, scientists opted for special relative which provided a way around this problem. However, the problem remained and is amplified in quantum uncertainty. To say that the Michelson-Morley experiment demonstrates the non-existence of ether is a complete misrepresentation. What those experiments demonstrate is that the nature of the ether is not understood

From the standpoint of the then current aether models, the experimental results were conflicting. The Fizeau experiment and its 1886 repetition by Michelson and Morley apparently confirmed the stationary aether with partial aether dragging, and refuted complete aether dragging. On the other hand, the much more precise Michelson–Morley experiment (1887) apparently confirmed complete aether dragging and refuted the stationary aether.[A 5] In addition, the Michelson–Morley null result was further substantiated by the null results of other second-order experiments of different kind, namely the Trouton–Noble experiment (1903) and the experiments of Rayleigh and Brace (1902–1904). These problems and their solution led to the development of the Lorentz transformation and special relativity. — Wikipedia

Take an electron for example. It must be a particle in the classical sense, because the structure of molecules and atoms is dependent on those particles. — Metaphysician Undercover

No, the classical sense (with absolute state) can be rejected altogether. On a relational model such as Rovelli's RQM, particles, atoms and molecules (and apples, desk lamps and human beings) are all quantum systems with relative state.

OK, so as I explained above to andrewk, I'll accept that a field is assumed to be more than imaginary. The problem is that it is modeled as the potential for activity, rather than a real active thing. So the issue is with the modeling technique, not the assumption that an imaginary thing is real. Therefore there is an inconsistency between the assumption, that the field is a real active thing, and the modeling of the field, as the potential for activity. — Metaphysician Undercover

On a quantum fields model, the fields for each particle type are real whereas it is particles that are potentials between interactions. For example, in the double-slit experiment the photon emitter acts by producing a disturbance in the electromagnetic field that propagates as a wave through the slits and toward the back screen. The wave represents a potential photon and a subsequent measurement actualizes the photon (say, at a slit detector or the back screen).

No, the classical sense (with absolute state) can be rejected altogether. On a relational model such as Rovelli's RQM, particles, atoms and molecules (and apples, desk lamps and human beings) are all quantum systems with relative state. — Andrew M

This is the point of the op then. The classical sense of "object" can be rejected altogether, and we no longer have any objective reality, everything is a "relative state".

On a quantum fields model, the fields for each particle type are real whereas it is particles that are potentials between interactions. — Andrew M

All you are doing here is constructing a double potential. The field itself is constructed as potential, then you layer another potential on top. This method of layering potential is not new in physics. Consider the concept of energy. As the "capacity" to do work, energy is fundamentally a potential, the potential for work. Then there is potential energy, and this is the potential for the potential for work. The double potential does not make energy actual, energy maintains its definition as a potential. Nor does the fact that the fields represent the potential for interaction between particles make the fields actual, they maintain their created status as potential. and we now have a double layer of potential.

That's what I've been discussing with andrewk, whether EM waves are real waves or not. Andrewk insists that "wave" is defined in physics in such a way that a medium is not required for a wave. But this is contrary to the Wikipedia page on waves in physics, and contrary to what I learned in high school physics, as well. I think andrewk is just fabricating a definition to support an ontological position, and asserting the correctness of that intentionally directed definition. — Metaphysician Undercover

Nah man. He ain't duping you bro.

field, n.: something that has a value everywhere in space

Physicists are pretending to be placeholders for rational thought by presenting statements based on mathematics non-geniuses and non-specialists don't understand. I think it's strange to comment that something is true or evident based on what someone has said unless you can make sense of it yourself mathematically and incorporate that math into the discussion--also having an audience or debate opponent with expertise in the same mathematics and a lot of time on everyone's hands.

Andrewk insists that "wave" is defined in physics in such a way that a medium is not required for a wave. But this is contrary to the Wikipedia page on waves in physics. — Metaphysician Undercover

From the Wikipedia page cited :

Electromagnetic waves do not require a medium. Instead, they consist of periodic oscillations of electrical and magnetic fields originally generated by charged particles, and can therefore travel through a vacuum.

.

The classical sense of "object" can be rejected altogether, and we no longer have any objective reality, everything is a "relative state". — Metaphysician Undercover

I don't think there is any such thing as 'the classical sense of an object'. What there has been, at various points in history, is the belief that there are real atoms, which are by definition 'indivisible particles'. But the existence of atoms in that sense has never been universally accepted.

Boltzmann's kinetic theory of gases seemed to presuppose the reality of atoms and molecules, but almost all German philosophers and many scientists like Ernst Mach and the physical chemist Wilhelm Ostwald disbelieved their existence.

(from the wiki page on Boltzmann.)

In any case, my thumbnail sketch of what quantum physics means, is that there is no 'ultimate object' in the sense proposed by atomism. Which, in turn, raises the question of what the fundamental constituents of nature are, or if indeed that is a valid conception at all. That doesn't imply relativism, either, as natural laws and mathematical logic hold for all observers. But I don't think they can be underwritten with reference to a purported indivisible material unit.

all the opponents of the Copenhagen interpretation do agree on one point. It would, in their view, be desirable to return to the reality concept of classical physics or, to use a more general philosophic term, to the ontology of materialism. They would prefer to come back to the idea of an objective real world whose smallest parts exist objectively in the same sense as stones or trees exist, independently of whether or not we observe them. — Werner Heisenberg

Reference https://www.physicsforums.com/threads/copenhagen-restriction-on-knowledge-or-restriction-on-ontology.968982/

In QFT, everything is described in terms of fields. A particle is a disturbance in the field, and it's always the field. There's only one electromagnetic field, for instance.

The double potential does not make energy actual, energy maintains its definition as a potential. Nor does the fact that the fields represent the potential for interaction between particles make the fields actual, they maintain their created status as potential. and we now have a double layer of potential. — Metaphysician Undercover

Are you not familiar with the idea of kinetic energy and the difference between that and the idea of potential energy?

So Wigner's friend measured a definite value while Wigner measured a value in superposition? I am trying to decide if it is worthwhile to read this paper.

This is the point of the op then. The classical sense of "object" can be rejected altogether, and we no longer have any objective reality, everything is a "relative state". — Metaphysician Undercover

Objects and objective reality remain, but counterfactual definiteness, an assumption from classical mechanics, is rejected. In other words, there is no view of an object from nowhere but only in relation to an observer (that is similarly internal to the universe).

As Banno analyzed earlier here, this already has a precedent in relativistic physics which is consistent with an objective reality.

In the case of the Wigner's friend experiment, Wigner sees interference while Wigner's friend sees a definite result. And QM is used to translate between the observations such that Wigner and his friend both agree that Wigner sees interference and Wigner's friend sees a definite result.

The field itself is constructed as potential, then you layer another potential on top. — Metaphysician Undercover

The field is not constructed as potential. QFT says that the physical things that we observe emerge from the interactions of more fundamental physical fields. That is, those physical fields (one per particle type) are part of the ontology of QFT.

In other words, there is no view of an object from nowhere — Andrew M

This emphasizes the fact that what's commonly thought of as objective is a psychic construction which happens to be mostly wrong.

Taking QM into account means we have to change which 3rd person statements we consider to be true. So the OP is really just a matter of semantics.

Are you not familiar with the idea of kinetic energy and the difference between that and the idea of potential energy? — Janus

Yes, but how does that make a difference? Energy is the capacity to do work, therefore a potential. Kinetic energy is actually having that potential by virtue of being active, and potential energy is potentially having that potential. So potential energy is a double layer of potential.

Consider it in Newton's terms, an apple is hanging in the tree, it has potential energy by virtue of gravity and the fact that it could fall. If it is falling, it has kinetic energy, and thereby has the potential to hurt someone, hitting them on the head. The falling apple has the potential to exert force (work). When it's in the tree, it has the potential to fall and thereby has the potential to have the potential to hit someone on the head, double potential.

As Banno analyzed earlier here, this already has a precedent in relativistic physics which is also consistent with an objective reality. — Andrew M

Redefining "objective reality" so that contradiction is acceptable in an objective reality is not what I would consider as an acceptable solution.

The field is not constructed as potential. QFT says that the physical things that we observe emerge from the interactions of more fundamental physical fields. That is, those physical fields (one per particle type) are part of the ontology of QFT. — Andrew M

As far as I understand "fields", they are always modeled as potentials, and this includes "the more fundamental fields" of QFT. If you understand them as a model of something actual, then I think you misunderstand the ontology of QFT. But perhaps I'm wrong, and you can show me how a field is modeled as something actual. Read what I said above to Janus "energy" refers to a potential.

I actually am not sure. — boundless

Well good. Being sure is being closed minded. I try not to be sure about anything, but I do it anyway.

I would not call what a table lamp does 'epistemic', so again, I do not personal hold view described there.
— noAxioms

Ok, I agree. Bad choice of terms on my part. For the sake of generality, let's just say 'not ontic' instead of 'epistemic' and drop using the word 'knowledge' in favor of 'addition of new 'information'' (for the lack of a better term).

The table lamp does acquire information (physics definition), so I can go with that.

Disturbingly close, yes, to the point where no arbitrarily close inspection will yield a difference. This is not true of the paper map of Paris.
— noAxioms

Again, you are right! I should have said, instead: 'non-representational' means that the wave-function simply does not have any ontological meaning.

It may or it may not. Wasn't this the thing we said we're not sure about? It seems quite interpretation dependent, even to the point of interpreting the meaning of 'ontological'. Tegmark's mathematical universe says that the wave function is what the universe is. It doesn't just describe it, but it actually is it. That's one kind of ontological statement: mathematics is fundamental, not just descriptive. Another kind would be two different interpretations of this mathematical universe where the mathematical structure has the property of existing (MWI variant) as opposed to RQM, where 'exists' is a relation, not a property. That's a different sort of ontological statement. RQM doesn't say that the universe doesn't exist (isn't nihilistic). It just gives no meaning to the phrase.

And no, neither MWI nor RQM needs to accept this mathematical foundation. I just used the mathematical universe example to illustrate two different kinds of ontology.

I am not sure if what you are describing here can be applied to the 'version' of RQM that I have in mind where after the observation, for the observer, the other branches do not exist.

Sounds like what I have in mind as well. For me, unicorns don't exist. For the unicorn, I don't exist. You seem to indicate that what I've described is something else.

BTW, I am sympathetic to some kind of realism for mathematics. I do not believe that mathematics is entirely a product of our minds but, at the same time, the usual version of mathematical Platonism does not convince me. So, maybe mathematical relations are 'real' (but not 'physical'). Interesting view

Or maybe they're physical but not real.

I would not call what a table lamp does 'epistemic', so again, I do not personal hold view described there.
— noAxioms

Ok, I agree. Bad choice of terms on my part. For the sake of generality, let's just say 'not ontic' instead of 'epistemic' and drop using the word 'knowledge' in favor of 'addition of new 'information'' (for the lack of a better term). — boundless

The table lamp does acquire information (physics definition), so I can go with that. — noAxioms

Ok let's keep 'information', then! :smile:

Again, you are right! I should have said, instead: 'non-representational' means that the wave-function simply does not have any ontological meaning. — boundless

It may or it may not. Wasn't this the thing we said we're not sure about? It seems quite interpretation dependent, even to the point of interpreting the meaning of 'ontological'. — noAxioms

Yep!

Tegmark's mathematical universe says that the wave function is what the universe is. It doesn't just describe it, but it actually is it. That's one kind of ontological statement: mathematics is fundamental, not just descriptive — noAxioms

Correct! There is a spectrum of views here.
Tegmark's position is that the Hilbert space is the only true reality, whereas our 3 dimensional space is merely an appearance. That's why in his view it is perfectly safe to say that there is no 'real' splitting.
On the other hand, one can even IMO in MWI take a less ontological view about the 'wave-function' (and the Hilbert space). I believe that a purely descriptive position is consistent with MWI.

Another kind would be two different interpretations of this mathematical universe where the mathematical structure has the property of existing (MWI variant) as opposed to RQM, where 'exists' is a relation, not a property. That's a different sort of ontological statement. RQM doesn't say that the universe doesn't exist (isn't nihilistic). It just gives no meaning to the phrase. — noAxioms

Good point! Existence is relational. The 'universe as a whole' is not in relation with anything, so 'existence' here does not apply. This does not imply that the universe 'does not exist', as you say :smile:

In other words, if we take this reasoning seriously we can speak of 'existence' in the presence of relations. If there are no relations, we cannot speak in terms of 'existence' (maybe of a different kind of 'reality', if 'reality' is taken as a more general term than 'existence'...).

And no, neither MWI nor RQM needs to accept this mathematical foundation. I just used the mathematical universe example to illustrate two different kinds of ontology. — noAxioms

Agreed!

I am not sure if what you are describing here can be applied to the 'version' of RQM that I have in mind where after the observation, for the observer, the other branches do not exist. — boundless

Sounds like what I have in mind as well. For me, unicorns don't exist. For the unicorn, I don't exist. You seem to indicate that what I've described is something else. — noAxioms

Thanks for the clarification but I still do not understand how you say that we can avoid some sort of 'selection' here.

To make it simpler, consider a radioactive decay experiment. There are two possibilities: Alice either observes the occurrence of the decay or not. Let's call these two possibilities, 'decay' and 'no decay' respectively. Let's also say that the probability of 'decay' is much less than the one of 'no decay'. Alice performs the measurement. And, say, she observes 'decay'.
If we do not accept the selection, we should accept that there is 'another Alice' that observes, instead, 'no decay'. And - besides the existence of 'another Alice' that observers 'no decay' - we have the different weights problem that occurs in MWI. In fact, this scenario is not very different from MWI. The only difference is that here we do not have a 'universal wave-function'.

On the other hand, if a selection is accepted, there is only one outcome.

BTW, the table on the Wiki article on the interpretations of QM, says that RQM is 'agnostic' about determinism. So, maybe RQM is simply silent about the selection.

[Also, IMHO unicorns here are not a good example. For me, they are simply impossible (but as you say, better not to be too dogmatic about this :wink: ).]

BTW, I am sympathetic to some kind of realism for mathematics. I do not believe that mathematics is entirely a product of our minds but, at the same time, the usual version of mathematical Platonism does not convince me. So, maybe mathematical relations are 'real' (but not 'physical'). Interesting view — boundless

Or maybe they're physical but not real. — noAxioms

I believe that 'real' is more general than 'physical'. In fact, I just cannot understand how mathematical relations can be 'physical'. :wink: