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Problems with Many Worlds Interpretation

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Ken G
#217
Sep14-11, 10:44 PM
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Quote Quote by Hurkyl View Post
Yes. That's all "rationalism" and "empiricism" are -- epistemological positions.
Not when the knowledge in question is about "what exists." This is the point of contact between epistemology and ontology, and it is exactly the place where CI and MWI differ. They just don't differ anywhere else. They certainly don't differ in the issue of how to know if a theory makes correct predictions or not, and they don't differ in the issue of whether or not observers and theorists need to confer on a joint agreement of what is a good theory. So they simply don't differ in any of the ways in which scientific knowledge is judged or obtained, except one: they differ on the issue of what constitutes true knowledge about what exists.
Er, that's a behavior.
Certainly not, not to the empiricist. Your claim here is, categorically, that how a mathematical entity depends on a variable t, makes a one-to-one claim on how some system behaves with the experiential and measurable concept of time. That just isn't true. You are missing that we are already affixing an interpretation to a physical theory that the parameter t in the theory corresponds to the empirically measurable concept of time. But it is not a necessary part of any theory that we must fail to distinguish between an experimental measure and a parameter in the theory (note for example that t is not an operator of quantum mechanics). It is part of the judgement of the value of the theory to connect that variable t to the empirical observation of experienced time, but only in the same empirical context that all theories are judged. No one ever says "I criticize your interpretation that t is time on the basis that it just doesn't seem like time to me", no, any criticism of that interpretation must be based on empirical comparisons of how the parameter t acts under experimental conditions. But we already know that the t that appears in the Schroedinger equation will not correspond to any experiential version of time if t is small enough, so the entire idea that "t" in QM is a continuous reflection of real time is simply false.
Ad hoc is necessary, but bad. The more ad-hoc a theory is, the less its ability is to make precise predictions, which in turn diminishes the value of any evidence favoring the theory.
MWI is just as ad hoc, but the ad hoc nature comes at a different level in the goals of the theory. CI adds an ad hoc physical postulate that some mysterious process, not covered by the theory, chooses which outcome we actually experience, MWI adds an ad hoc metaphysical postulate (as you did above) that our particular individual experience is a question that physics should not be interested in. CI sees that as cheating-- it's not surprising that greater unification can be achieved by allowing ourselves to cheat on what a theory should describe (rather than on how it should describe it, that was Einstein's objection about dice).
No. MWI is motivated by the question "Can a mathematically unified method explain what I perceive?"
It can't be that, because it fails to do that. Also, note that CI is just as mathematically unified as MWI. It has to be, it's all the same mathematics. MWI is not content with mathematical unification, it wants ontological unification. And it can only accomplish it by dodging the question of why I perceive what I perceive. I still haven't seen your answer to that. Your scenario doesn't answer it, because we don't have an observer getting <heads,tails>, we have a bundle of perceptions connected with the sentient being I'll call observer1, and a bundle of perceptions (according to MWI) connected with sentient being observer2, whose perceptions do not overlap and they do not perceive each other. So what you'd have to say is, you have <observer1,observer2> reporting <heads,tails>. If you do that, the mathematical description is entirely unitary, but you have no way to account for why it did not come out <observer1,observer2><tails,heads>. All you could say is that you don't care about the difference there-- but try telling that to observer1 if "heads" means he loses his.
I think you mean some sort of Platonism, rather than rationalism.
Platonism is quite a bit different from the way MWI is normally expressed. Indeed, I would have no problem with MWI as a form of Platonism, that is the sense in which MWI makes reasonable claims. The key difference is that Platonism draws a distinction between what is physically real and what is abstractly real. If people want to imagine that the many worlds are abstractly real, as some form of perfect concepts, I would have no issue with them other than being a bit idealistic. It is the claim on physical reality that I feel should require empirical demonstration. When someone can empirically demonstrate the existence of many worlds, only then would I find it appropriate for us to conclude that they are physically real.


Formally, at least, theories are syntax and truth is semantics, there's no if's, and's, or but's about it. And I'm enough of a formalist to believe that anyone who claims otherwise really just hasn't learned to mentally separate the ideas of "theory" versus "interpretation".
I completely agree, that was the flavor of Godel's proof-- syntax and semantics can never be the same thing in any formal system rich enough to be suitable for our purposes. Indeed that is my entire issue with how MWI is normally expressed-- it improperly crosses that dividing line, mistaking a syntactic interpretation for a semantic one. That's also the place where ontology creeps in.
I strongly disagree. It is very, very difficult to consider an empirical "truth" without having first filtered it through one's intellect. I would be so bold to claim it impossible to do so completely.
That's true, it's the bugbear of formal empiricism that brainless entities can't do it. All the same, it is pretty clear when a consistency of perception has been identified. That's why reading of pointers can be done by almost anyone, but predicting those readings can be done by rather few. The rationalistic perspective about what is true knowledge regarding what exists is quite elitist, and suffers the flaw that a much more intelligent species than we will likely form a completely different view, one that we simply cannot understand any better than most plumbers understand string theory. Yet the plumber knows what he experiences, so the empiricist version is a more accessible ideal about what constitutes truth. Empiricism also avoids the troubling "truth is only as good as your current theory" problem that dogs rationalism.

Still, I grant you that neither rationalism nor empiricism can make a self-contained case, and that's probably why we need a combination to do science. Perhaps we have more to learn from the tension between the CI and the MWI, than we have to learn by marrying one or the other. But I completely agree with Fredrik that you are mischaracterizing CI when you say that it adopts essentially supernatural claims about the ontology of collapse-- instead, CI adopts a solipsistic perspective on collapse, it merely accepts collapse as real on the basis that we experience it, and unitarity as unreal on the basis that we do not experience it. CI takes no other position on the matter, there is no sense that "a miracle happens" when collapse occurs-- instead, collapse is what happens, the two are exactly the same concept in every way. That's why I said that unitary evolution is not a behavior at all in CI, it is just the language of how to predict, statistically, the next behavior, the next collapse. There is nothing in the empirical meaning of our word "behavior" that is not also in the word "collapse," so there is no need to attribute any mystical or miraculous elements to the latter word.
Ken G
#218
Sep15-11, 12:04 AM
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Quote Quote by Hurkyl View Post
MWI is certainly capable of talking about whether a subsystem is in a pure state or approximately in a pure state or not.
I suppose that depends on what one means by a subsystem. Many people, including on this thread earlier, talk about subsystems in MWI as associated with a particular particle that has some identifiable consistency across branches. In that language, no subsystem is ever in a pure state-- if I pass an electron through a Stern-Gerlach and accept all the ones taking the spin up path, none of them are in the state "spin up", they are all in a mixture of <spin up, accepted> and <spin down, rejected>. That's not a pure state, because there is no definite phase relationship between those terms, the phase is decohered. All the same, the experimenter doing quantum mechanics will deal only in the pure state <spin up, accepted> when he/she talks about the electrons in the accepted path, and MWI can deal with the fact that the projection onto that experimenter's acceptance decision will look like a pure state. But in MWI, that experimenter is under an illusion that the reality of the particle state is something different than what it actually is, because the experimenter's version cannot result from unitary evolution prior to the experiment, even as he/she uses unitary evolution to predict the subsequent behavior.
The big idea is that nobody has a birds-eye view. Therefore, any philosophical assertions about how the birds-eye have no scientific basis. I assert the analogy:
CI is to MWI as Lorentz Ether Theory is to Special Relativity
I take your point about nobody having a birds-eye view, so that the ontological description must in a sense be cobbled together from all the birds-eye views. However, I reach the opposite conclusion along that same logical path! I see the analogy as:
MWI is to CI as Lorentz Ether Theory is to Special Relativity
We agree that a consistent ontology needs to be patched together from objective observer's perspectives, but what goes into the patchwork? LET attempts to find a single truth that in some sense regulates all the observations, the aether, whose existence relies entirely on a rationalistic desire to unify the reality of all observers into a single description of "what is actually happening even though we never see it." That's a lot like what MWI does, it takes an ontological stance on what is happening in a way that we never actually see. But SR, like CI, rejects any ontology that involves entities we never see. SR elevates to the level of a metaphysical principle that if nature conspires to keep some ontological entity hidden, then it must be part of our interpretation that such an entity does not exist.

On the other hand, the role of decoherence as seen in MWI sounds an awful lot like how Lorentz imagined that the aether must be monkeying with our experimental apparatus to fool different observers into seeing different things, all within a single unified mathematical description. In other words, Lorentz interpreted his contractions ontologically, whereas Einstein made it a core value that if there is no empirical imperative for the contraction, then the contraction was not ontological at all, it was merely relative to the observer. In short, the set of observers that can share notes with each other, and their observations, is what defines the reality, reality is not tricking them or leading them into illusions. Yet that's just what it is doing in the MWI, so to me, the MWI sounds a lot more like LET in its stress on a consistent ontology instead of just querying a demonstrable collection of observers and take their reports at face value.
What I really want to do is to do the very thing my analogy above suggests: once we can entertain the notion that unitary evolution of wave-functions can adequately describe our experiences, we can then take the next step and notice there are many wave-functions* that are empirically indistinguishable, and so we can switch between them at our leisure.
I can agree that what reality does not distinguish as different is not different. I don't yet see why that has a different flavor in MWI than in CI.
In particular, collapsing a wave-function when you observe something just becomes an example of changing your frame of reference.
I will grant you that is a valid insight, I can see elements there that would justify your analogy. If, for some reason, all the observers in our universe had to always be in the same one inertial frame, they might quite likely have come up with something like LET rather than SR. Their frame would have seemed very special, and when elementary particles at high speed took a long time to decay, they might have assumed something was affecting them, like a Lorentz aether. They would never have encountered an observer in a different frame, so they would not have cast the result in terms of invariants for that other observer, but rather in terms of physical effects on the elementary particle. But to that I have two immediate reactions:
1) if all the observers in the universe had to all be in the same inertial frame, there would be good justification for LET over SR, because there would seem to need to be a darn good reason for being all in the same frame, and
2) if we will think of MWI as a kind of transformation to observers in other reference frames, then what is the equivalent to the invariants that SR builds reality from? There is no equivalent to the norm of a 4-vector, which is empirically constructed. Instead, the only invariant I can see is the unitarity, but that is not empirically constructed, it is purely a rationalistic invariant. There is no function that takes as inputs each observers findings and generates a common scalar out of them, such that we could say our theories must only refer to those scalars.
How would I tell the difference? Not only do I not possess any empirical evidence that I don't hear the words "<heads,tails>", I have no idea what such evidence would look like.
But that's just the point-- that you have no idea what such evidence would look like is the proof that you do not experience it.
I would perceive "heads or tails" because <heads,tails> is what really happened.
That's not what you perceive when you flip a coin one time-- you do not experience "heads or tails", you experience heads, or you experience tails, which is something different .
Fra
#219
Sep15-11, 12:33 AM
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Quote Quote by Fredrik View Post
I have some issues with the word "describe". I would choose to talk about making accurate predictions about results of experiments instead.
Yes you're right, but I deliberately used the word describe to sharpen the point.

But there is no difference in what I refer to as "describing the future" and "predicting the future"; except in the way you understand what the point of "prediction" IS, and that's exactly my point (a) vs (b).
Quote Quote by Fredrik View Post
However, I don't think it's necessary to mention this in every thread about quantum mechanics, which clearly is a theory in the sense of what I like to talk about: It assigns probabilities to verifiable statements.

I also wouldn't describe a speculative new idea as one of the two "main" things that the term "theory" can refer to.
I don't mention it every thread. But the discussion in this thread is IMHO not so much about physics as it is about philosophy of physics. After all these discussions about the same old interpretations often (to me) seems non-constructive as noone rarely makes a point that aims to make a difference.

Also, it seems to me that I'm one of the few that represent these ideas on here, so for the benefit of a health discussion at least I feel I'm providing a fresh (possibly constructive, each one can judge that on their own) perspective to the discussed topic.

/Fredrik
Eqblaauw
#220
Sep15-11, 01:15 AM
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I think it would be philosophy if we talked about the consequenses on our daily lives if mw where true. Wich are pretty big, especially if you talk about the splitting variant, that lives on while being denied by prominent proponents of mw. For example when someone dies in a quantum (chance) event you will feel a lot different when you believe he/she lives on in most of the (many, many) worlds. Sure it's sad you don't see him/her anymore, but that certainly isn't all we grieve about at funerals,
also it makes every history book seem pretty trivial
But making speculative claims about the physical existense of things isn't philosophy, it isn't even bad philosophy. Just speculative science (good or bad, it's up to you. Bad I would say, but hey).
Dmitry67
#221
Sep15-11, 06:02 AM
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Quote Quote by Ken G View Post
It sounds like there are two "me"s here, an "F" me and a "B" me. Will the real me please stand up! When did the "B tree of me" begin, anyway?
Sure, but please provide a definition of "being real" first.

Your tree had started when you were born. In some alternatives you were born earlier/later and in different conditions, I dont know how operation = (equals) works for the consiousnesses, so I can't say if they also belong to "you"

The same issue you have in Infinite Universe even without MWI, just alternative/copies are separated spacially.
Eqblaauw
#222
Sep15-11, 07:00 AM
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semantic philosopher when someone says you get an icecream and you get one it is real when someone says that and he gives you nothing it is not real, there is nothing hard about something being real
and don't say define icecream
Ken G
#223
Sep15-11, 09:08 AM
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Quote Quote by Dmitry67 View Post
Sure, but please provide a definition of "being real" first.
That's indeed the question. To a CI proponent, "being real" means "demonstrable by experiment"-- what is real is what is experienced by objective observers that we can (in principle) communicate with. To a MWI proponent, being real means fitting in with a mathematical structure that is generated by the minimal and most unifying conceptual principles. So to be consistent, both of the interpretations must build their models of what "I" am from similar stuff. That's going to be a lot easier for CI, because "me" is whatever I perceive myself to be, and the experiences of "me" are nonunitary.
Your tree had started when you were born.
Not when I was conceived? What if I am born dead in some branch, and alive in another, do I need to be born alive to count in the "me" tree? When does the "me tree" end, if there is always some branch in which I am still alive, no matter how rare? What if I'm a vegetable in some tree, does that suffice to keep the "me tree" going?
In some alternatives you were born earlier/later and in different conditions, I dont know how operation = (equals) works for the consiousnesses, so I can't say if they also belong to "you"
Well, that's certainly going to be a problem you will need to work out before you can claim that MWI can account for "my" perceptions. Note how much easier it is for CI-- there, my perceptions are just my perceptions.
The same issue you have in Infinite Universe even without MWI, just alternative/copies are separated spacially.
Not in CI, because alternative copies are irrelevant in CI-- my perceptions are just what they appear to be, and I don't perceive any copies of me, so I have no reason to account for them. I don't need them to recover my unitariness, I can be just as nonunitary as I perceive myself to be.
Eqblaauw
#224
Sep15-11, 09:24 AM
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[QUOTE=Ken G;3503575]That's indeed the question. To a CI proponent, "being real" means "demonstrable by experiment"-- what is real is what is experienced by objective observers that we can (in principle) communicate with. To a MWI proponent, being real means fitting in with a mathematical structure that is generated by the minimal and most unifying conceptual principlesborn alive to count in the "me" tree?

Yes but what dimitri is implying is that there are different definitions for 'being real'. That's gibberish, both miw-ers and ci-ers have exactly the same definition of 'being real' they just think it applies to different things.
Fra
#225
Sep15-11, 09:54 AM
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With the high risk of beeing misunderstood...
Quote Quote by Ken G View Post
To a CI proponent, "being real" means "demonstrable by experiment"-- what is real is what is experienced by objective observers that we can (in principle) communicate with.
At first sight, this means "real" is defined by whatever the set of any classical observers will agree with infer from "experiments". The idea is that even if there are some differences, due to inertial frame, in principle one can classsically recover an equivalence group of observers that defines "reality" as invariants of the set of observers whose observations are related by known transformations. It's in this specific sense that "reality" exists independnet of observation EVEN in CI!

Thus the "realism" here is applied to the set of agreements between classical observers. Ie. this is even take to be a "consistency requirement".
Quote Quote by Eqblaauw View Post
Yes but what dimitri is implying is that there are different definitions for 'being real'. That's gibberish, both miw-ers and ci-ers have exactly the same definition of 'being real' they just think it apply's to different things.
Someone else get to elaborate for MWI, but there is similary some structures where "realism" is applied

So in this sense I see what you say.
Quote Quote by Eqblaauw View Post
there is nothing hard about something being real
But I think the above is a simplification.

Since I consider myself coming from CI, while currently beeing more radical I can most easily explain what I mean by noting what's wrong in the CI picture above:

The core point is objectivity. Essentially the laws of physics MUST be the same to all observers. Thus realism applies to physical law. But this a subtle breach with the scientific ideal of empirism, which seems to more advocate effective laws, rather than "objective laws".

Instead of thinking of the indeed sounds (almost obvious) requirement of a scientific theory to be observer independent (or scale covariantly) in a predictable way, and thus consider objectivity to be

- a LOGICAL CONSTRAINT on the theory; prime examples are special as well as general relativity. Here realism as "observer independence" is a CONSTRUCTING principle. Einsteins insight was that, it does not make sense of different observers "sees" different laws - thus in the search for a covariant theory this is a key insight.

This is by the way the "normal" and by far dominating way to understand it, even today, even in QM.

- or as a form of equilibrium condition for emergent objective, in terms of observer democracy. This picture seems to be preferred by a empirist perspective since after all, laws are abductions from experiments, not deductions. I do not anyone can deny that.

It sounds like Eqblaauw's point is that both CI and MWI talk contains realism, just in different forms, here I agree.

But we don't have to settle with this, so here I disagree that what's real is a triviality.

/Fredrik
Eqblaauw
#226
Sep15-11, 10:11 AM
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yes my point is both have the same definition of 'real', but they just think other things are real based upon the method/interpretation they choose.
I'm aware I speak for MIW, but this is just in the best faith.
If some theory chooses another definition of real then this is only bound to give confusion, and they should use another word.
Samshorn
#227
Sep15-11, 10:30 AM
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Quote Quote by Ken G View Post
...what you'd have to say is, you have <observer1,observer2> reporting <heads,tails>. If you do that, the mathematical description is entirely unitary, but you have no way to account for why it did not come out <observer1,observer2><tails,heads>. All you could say is that you don't care about the difference there-- but try telling that to observer1 if "heads" means he loses his.
What is the significance of your observer labels 1 and 2? I think a MWI advocate would say that, if we have a sequence of 50 coin tosses, there are 2^50 distinct observers, one for each possible sequence of outcomes, and we identify those observers with their respective sequence of outcomes. So it's self-contradictory to talk about permuting the observers to different sequences of outcomes. The sequences of outcomes ARE the observers.

By the way, Deutsch has argued that observers (and universes) not only proliferate, they must also re-aggregate, and hence it is possible in principle for an observer to remember a superposition of histories. So there are versions of MWI that are compatible with observers perceiving superpositions, and there are versions of MWI that are compatible with observers NOT perceiving superpositions. Then, applying my "second quantization" meta-interpretation MMWI (Many Many Worlds Interpretation) [Trademark] the universe is actually a superposition of Many Worlds's, in some of which the identities re-aggregate and in some of which they do not. (I've already trademarked all the other MM...MWIs too, so don't even think about it.)
Fredrik
#228
Sep15-11, 10:35 AM
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I don't think it makes sense to ask for definitions of terms like "real", "exists" and "describes" when we're talking about definitions of QM. They should be considered primitives (i.e. terms left undefined).

If I had to define it, I would say that a "mathematical thing" in the theory is "real" if it's directly measurable, like momentum. But this is obviously not what anyone has in mind when they discuss interpretations of QM. They mean "real" in the sense of how you have understood the term since you were a kid. Polar bears are real, Santa Claus isn't.

This explanation isn't a definition, since it doesn't associate the term with a specific mathematical or physical object. It's an "elucidation". (That's what a book I own calls an explanation of a primitive).
Eqblaauw
#229
Sep15-11, 10:54 AM
P: 40
Polar bears are real, Santa Claus isn't.

This seems a pretty good example to me. But I have to stand up for the Tegmark-like MWIers who think there probably is an immortal ('since we all are immortal') Santa Claus somewhere, riding his fuled sleigh to make all the little children happy.
And no this isn't a strawman
Ken G
#230
Sep15-11, 11:22 AM
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Quote Quote by Fra View Post
The idea is that even if there are some differences, due to inertial frame, in principle one can classsically recover an equivalence group of observers that defines "reality" as invariants of the set of observers whose observations are related by known transformations. It's in this specific sense that "reality" exists independnet of observation EVEN in CI!
I think I see what you are saying, but I would elaborate on it a little. Relativity doesn't actually say that reality is something other than what the observers perceive, it says two things:
1) what an observer experiences is not separable from that observer, so reality must include only an account of dual entities like < observeri | observationn >
2) any theory used to describe or predict reality must be built from a special type of invariant, a type involving a mapping from the entities < observer[sub]i[sub] | observationn> into some observer-independent scalar [special invariant]. The [special invariant] is free of any need to refer to an < observer|, but note that <observeri|observationn> is already an invariant, all observers will agree that that observer got that result. But the theory will not refer to invariants like that because they involve explicit mention of some observer, so relativity theory is built not just from any old invariant, like <observeri|observation>, but only from norms of 4-vectors, whose components look like <observeri|observationn> in the basis <observeri|, for a special class of n. Those components are not invariants when regarded as coordinates that stay the same in any basis, but they are invariants when regarded as the projection of an observation onto an observer.

In short, some invariants are frame-dependent, not in that they change from frame to frame, but that they require the identification of a frame in order to exist. Relativity doesn't use that type of invariant to build its laws about reality, but it does not deny that such invariants are part of reality. So I would say the lessons of relativity are:
1) a consistent concept of reality must be an account for all the invariants <observeri | observationn> so also any function f(<observeri | observationn>)
2) a description of the laws on such a reality must be built from a higher-order form of invariant, which is a function on the invariants that do reference an observer frame, and the function produces a scalar output that is the same for any (inertial) observer frame referenced. So we have the kind of "invariant" that relativity talks about, which is really any sum of <observeri | observationn>2 with the appropriate signature as n ranges over the indices of a 4-vector. It is a special construction from the invariants that do refer to a reference frame, resulting in a special invariant that does not so refer.

Now, relativity says the laws have to be constructed from these 4-vector-norm type of invariant, but they still have to predict all the invariants, like the <observeri | observationn>. The latter requires something more than the laws, it requires boundary and/or initial conditions-- the "hidden" element of any physical theory that doesn't get counted as part of the laws of the theory, but the theory doesn't work without them.

So I would say that reality in relativity only exists independently of observations if one is strictly considering the laws of relativity, and ignoring the essential role of boundary conditions to condition the outcomes that we will actually test in order to judge if the theory works. When we generalize the theory to include the way it processes boundary conditions, then we need to include all the invariants, including the ones that refer to a particular reference frame, since they will be needed for the theory to do what we want it to do-- predict invariants that do refer to particular reference frames. The reality, then, is still the latter-- not the laws. That's the empiricist stance on relativity-- the reality always refers to reference frames, but the laws do not. The MWI/rationalist analog would be to say that the laws are the reality, and the boundary conditions and outcomes we use to test them are just some kind of arbitrary illusion, not important to the reality (but essential to testing the theory).
The core point is objectivity. Essentially the laws of physics MUST be the same to all observers. Thus realism applies to physical law. But this a subtle breach with the scientific ideal of empirism, which seems to more advocate effective laws, rather than "objective laws".
Interesting point, it sounds like you are an empiricist with rationalistic leanings! The pure empiricist does not have an issue translating between effective and objective laws-- they simply say that the two are the same, for a law to be effective it must be objective. The objectivity still stems from the empirical set of <observeri | observationn> entities that define reality (where the observers can be hypothetical, the issue here is to generate a language about reality), but it is natural to require that any laws that effectively govern or predict those objective entities must themselves be objective, even if they are just effective laws. The rationalist always asks, how can reality do anything but obey laws, and the empiricist responds, how would reality know how to obey anything, especially not laws that we keep changing-- reality just is.
Ken G
#231
Sep15-11, 11:35 AM
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Quote Quote by Samshorn View Post
What is the significance of your observer labels 1 and 2? I think a MWI advocate would say that, if we have a sequence of 50 coin tosses, there are 2^50 distinct observers, one for each possible sequence of outcomes, and we identify those observers with their respective sequence of outcomes. So it's self-contradictory to talk about permuting the observers to different sequences of outcomes. The sequences of outcomes ARE the observers.
Yes, exactly-- I expect that many (most?) MWI advocates simply define the observer by what they observe. That means you are defined by your perceptions, you are not a kind of "vial" that gets filled with perceptions. That's what I mean by a "model of me" that is required in MWI. The problem is, whenever we make a model for one purpose, like interpreting quantum mechanics, we have to live with that same model in every other way, if our claim is going to be that we have a consistent and complete view. So then we need to ask, is this really the "model of me" that works, that I am defined by my experiences? Note how completely that undoes the standard empiricist perspective on reality-- we take ourselves as given, and use our experiences to say what reality is. That's what separates the scientist from the mystic. We don't take reality as given, and use our experiences to say what we are, that's essentially a mystic stance. You can do it either way and everything works, but you have to accept the full package of the rationalist perspective if you're going to go that road. I have no objection to MWI other than that many of its proponents seem to think they are just doing physics, rather than adopting a fairly radical rationalistic philosophy of who we are and what knowledge of reality is. Are you simply defined as the person who lives in a scientific reality?
Eqblaauw
#232
Sep15-11, 11:55 AM
P: 40
I would like to give zeno's paradox as an example about something that makes mathematical sense for centuries, but we simply know by experience it is false. I,m not saying mwi directly controdicts are experiences, but there aren't any experiences that account for it. To paraphase brian greene (not a fan) math tells us what may be possible, expirements have to tell us what is. There may be some experiments in the future (mwiers sometimes say this as if this itself alone is an argument for the theorie) but now there isn't. So now it's a hypothesis, and nothing more, and if you want to say it's true you just have to wait till there is any empirical evidence whatsoever. If there ever will be.
fleem
#233
Sep15-11, 12:42 PM
P: 461
Well, the thing about Zeno's paradox is that it does what I'd call "reverse-normalization" (abnormalization?). Normally if we have infinities in a problem we find a way to remove them. Zeno's paradox is just an indication that if we're crazy enough we can intentionally add infinities to any problem.
Hurkyl
#234
Sep15-11, 12:51 PM
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Quote Quote by Ken G View Post
Your scenario doesn't answer it, because we don't have an observer getting <heads,tails>, we have a bundle of perceptions connected with the sentient being I'll call observer1, and a bundle of perceptions (according to MWI) connected with sentient being observer2, whose perceptions do not overlap and they do not perceive each other.
(There was only one sentient being on my scenario. The mathematical description is identical to a different scenario with two observers that we talk to simultaneously -- but we're not doing that thought experiment, we're doing a thought experiment with a single observer in a universe that admits indefinite outcomes)


but try telling that to observer1 if "heads" means he loses his.
Me: *applies hypnosis* You will kill yourself if your first coin flip was heads.
Experimenter: <okay. *bang*, phew good thing I got tails>
Me: So, how are you feeling?
Experimenter: <no response, pretty good>
....
Your scenario doesn't answer it, because we don't have an observer getting <heads,tails>
That's because it was the starting point. If one really wanted to (and had the details), one could wind back in time and find the state of 5 seconds in the past, and then see that <heads,tails> was the (deterministic!) time evolution of that state.

If that's not an answer to your question, then I think you're starting to ask questions akin to "Why was the universe created in such a way so that we're sitting here posting on an internet forum during the September of 2011?"

Also, note that CI is just as mathematically unified as MWI.
Really? CI has found a way to unify unitary evolution and collapse? Can you provide a reference?

And it can only accomplish it by dodging the question of why I perceive what I perceive. I still haven't seen your answer to that.
The answer is trivial -- you perceive what you perceive because it's encoded in the wave-function. And the wave-function is what it is because it was the unitary evolution of the wave-function of the past.

You're rejecting the answer because you want reality to adopt a definite outcome, and you don't think a frog's eye view of definite outcomes is good enough, you are insisting that they are definite in the bird's eye view as well.

It can't be that, because it fails to do that.
It sure looks like it does to me. Consistency of observation is explained. That different observers agree upon what is observed is explained. Empirical frequencies are explained.

So what is left unexplained? The thing you keep insisting is unexplained is a quality of reality that is imperceptible.


Certainly not, not to the empiricist.
In your own words:
And the correct response of the CI person is: ... They evolve in the parameter time, in exactly the way QM says they do,
If, for whatever strange reason, you define the English word "behave" in a way that the above isn't a behavior, then whenever you see me using the word, you should mentally substitute whatever word you find more appropriate.





MWI adds an ad hoc metaphysical postulate (as you did above) that our particular individual experience is a question that physics should not be interested in.
You've changed the question again. Our individual experiences are interesting. What is not interesting is the supposition that reality adopts a definite outcome.


MWI is not content with mathematical unification, it wants ontological unification.
I'm not interested in whatever straw man you are intent on setting up to attacking. I'm interested in the the hypothesis that collapse is not required to get the correct predictions from QM -- in particular the qualitative behavior of our observations.



Platonism is quite a bit different from the way MWI is normally expressed.
Where the heck did this train of thought come from?


Indeed that is my entire issue with how MWI is normally expressed-- it improperly crosses that dividing line, mistaking a syntactic interpretation for a semantic one.
I can't even begin to make sense of this.


CI adopts a solipsistic perspective on collapse, it merely accepts collapse as real on the basis that we experience it,
This does not follow without the additional ontological postulate that reality adopts a definite outcome.

and unitarity as unreal on the basis that we do not experience it.
What evidence do we have that we do not experience it? What experiment could possibly give different results between the two cases of definite and indefinite outcomes?


instead, collapse is what happens
Yes, that is the interpretation of QM.

the two are exactly the same concept in every way.
And this is an ontological postulate about an imperceptible aspect of reality.


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