Copenhagen Interpretation of Sleep / Unseen brain?

[bhobba]

Is the predictability sieve the stability criterion? If it is not, please state the stability criterion exactly.

It usually boils down to its associated observable commuting with the Hamiltonian - and is referred to as the commutativity criteria. See page 77 of Schlosshauer.

Its rare that this criteria doesn't work, but evidently it has been generalised, and that is where your predictability sieve comes in (see page 82 Schlosshauer)

Delving deeper into it really requires going through the book. Its been a while since I have delved into this detail, so if that's what you want to do I am afraid I will have to leave it up to you.

Thanks
Bill

 

[atyy]

It usually boils down to its associated observable commuting with the Hamiltonian - and is referred to as the commutativity criteria. See page 77 of Schlosshauer.

Its rare that this criteria doesn't work, but evidently it has been generalised, and that is where your predictability sieve comes in (see page 82 Schlosshauer)

Delving deeper into it really requires going through the book. Its been a while since I have delved into this detail, so if that's what you want to do I am afraid I will have to leave it up to you.

So now that you find the predictability sieve mentioned, do you agree that P is an assumption?

 

[atyy]

It is this that is the key to solving the issue Schroedinger's cat was on about. Copenhagen did not give a precise definition of a measurement. Decoherence does. Using that its obvious the cat has nothing to do with anything - it happens at the particle detector.

Now that I understand your ignorance interpretation a bit better - I had thought it was a variant of Copenhagen, but it isn't - your ignorance interpretation has an absolute quantum/quantum cut, whereas the cut of Copenhagen is not absolute and can be shifted.

Given that you agree that there is not a known prescription for F, how can you say that it happens at the particle detector? If you merely assert that F exists, how can you rule out that the cut is at the box, and so wouldn't there be a version of your ignorance interpretation in which the cat is in a superposition of dead and alive?

 

[bhobba]

Given that you agree that there is not a known prescription for F, how can you say that it happens at the particle detector? If you merely assert that F exists, how can you rule out that the cut is at the box, and so wouldn't there be a version of your ignorance interpretation in which the cat is in a superposition of dead and alive?

You simply trace it back to find the earliest point decoherence occurs.

Thanks
Bill

 

[atyy]

You simply trace it back to find the earliest point decoherence occurs.

So is the wave function real in your ignorance interpretation?

 

[bhobba]

So is the wave function real in your ignorance interpretation?

It's ambivalent.

Thanks
Bill

 

[Derek Potter]

You simply trace it back to find the earliest point decoherence occurs.

Surely (is that diffident enough?) that need not be at the detector? A typical alpha particle leaves a trail of ionisation in air, so decoherence should be pretty complete within a few microns of the source.

 

[bhobba]

Surely (is that diffident enough?) that need not be at the detector? A typical alpha particle leaves a trail of ionisation in air, so decoherence should be pretty complete within a few microns of the source.

Valid point. If you can take it back further depends on exactly how the detector works.

Thanks
Bill

 

[atyy]

It's ambivalent.

So what is real in this interpretation?

I'm asking, because I would like to know in what space F is defined.

For example if the detector is real, what are the degrees of freedom that allow you to say - the cut is at F?

Also, assuming there are degrees of freedom or at least beables that describe the detector - what is there are two Schroedinger cat experiments run simultaneously (defined in an inertial frame) in different parts of the world. Where is F?

 

[bhobba]

So what is real in this interpretation?

Observations.

With two experiments each has its own particle and detector.

Thanks
Bill

 

[atyy]

Observations.

With two experiments each has its own particle and detector.

Is the particle real? Is the detector real?

 

[Derek Potter]

With two experiments each has its own particle and detector.

And its own cat. We must never forget the cats :)

 

[bhobba]

Is the particle real? Is the detector real?

Atty I think you know my view on that. Reality is what our theories specifically state in our axioms. For QM that would be the classical macro world and the observations that occur in it. Its of course an issue exactly how that classical world emerges from a theory that assumes it in the first place. A lot of progress has been made in resolving that but from what I read some issues still remain.

Thanks
Bill

 

[atyy]

Atty I think you know my view on that. Reality is what our theories specifically state in our axioms. For QM that would be the classical macro world and the observations that occur in it. Its of course an issue exactly how that classical world emerges from a theory that assumes it in the first place. A lot of progress has been made in resolving that but from what I read some issues still remain.

That is very confusing! That sounds like Copenhagen, and saying that how the classical world emerges is an issue sounds like there is a measurement problem. But I thought you said your interpretation solves the measurement problem. If it does, how can there still be an issue of how the classical world emerges?

 

[bhobba]

That is very confusing! That sounds like Copenhagen, and saying that how the classical world emerges is an issue sounds like there is a measurement problem. But I thought you said your interpretation solves the measurement problem. If it does, how can there still be an issue of how the classical world emerges?

There is a measurement problem - remember the third part that decoherence is no help with - why we get any outcomes at all. This existence of a classical world is tied up with that.

Thanks
Bill

 

[atyy]

There is a measurement problem - remember the third part that decoherence is no help with - why we get any outcomes at all. This existence of a classical world is tied up with that.

There is a measurement problem in your ignorance interpretation?

 

[bhobba]

There is a measurement problem in your ignorance interpretation?

Of course. I have always said so. It however has morphed to why we get any outcomes at all.

Thanks
Bill

 

[atyy]

Of course. I have always said so. It however has morphed to why we get any outcomes at all.

OK, I don't quite agree with that description of the measurement problem, but now I'm less confused. I thought you were saying that there is no measurement problem in your ignorance interpretation.

If decoherence doesn't solve the measurement problem, then there isn't a tidy answer to my question, right?

Yes there is - its just not unique. Decoherence however has morphed the issue to - why do we get any outcomes at all.

The answer is called an interpretation of which there are a plethora.

I copied the above from your reply to 1977ub earlier in the thread, and it certainly made it seem that you were saying that there are many solutions to the measurement problem, which is what I was disagreeing with. Then I thought you were bringing up your ignorance interpretation as an example of a solution to the measurement problem.

 

[Derek Potter]

For the sake of the slow-witted who may still be trying to glean something from this thread, could you please explain why getting any outcomes at all is a problem?

edit - I don't mean I don't think it is a big issue, I just don't know what you mean by it.

 

[bhobba]

For the sake of the slow-witted who may still be trying to glean something from this thread, could you please explain why getting any outcomes at all is a problem?

It doesn't explain why you do. Technically it's why an improper mixed state is a proper one.
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

Thanks
Bill

 

[Derek Potter]

It doesn't explain why you do. Technically it's why an improper mixed state is a proper one.

I don't understand why we have to have a proper mixed state. What's wrong with an improper mixed state if it does the job of explaining the appearence of outcomes?

 

[atyy]

I don't understand why we have to have a proper mixed state. What's wrong with an improper mixed state if it does the job of explaining the appearence of outcomes?

I don't totally agree with bhobba's way of stating the measurement problem, but I think I understand it. What he means is that if we just have a unitarily evolving wave function, we clearly have no outcomes unless there are some additional assumptions. So the job of any interpretation that solves the measurement problem is to add assumptions that produce the outcome. For example, many worlds adds the assumption that blah, blah, blah ...

 

[Derek Potter]

QUOTE="atyy, post: 5163488, member: 123698"]I don't totally agree with bhobba's way of stating the measurement problem, but I think I understand it. What he means is that if we just have a unitarily evolving wave function, we clearly have no outcomes unless there are some additional assumptions. So the job of any interpretation that solves the measurement problem is to add assumptions that produce the outcome. For example, many worlds adds the assumption that blah, blah, blah ...[/QUOTE]

"Many worlds"? Never heard of it.

I'll put my question another way. Rather than asking how measurement creates a proper mixed state, shouldn't we ask whether it actually does so?

Why do we need outcomes at all? We know that measurements create the appearence of outcomes in the macro world, but the improper mixed state that bhobba referred to (and which does follow from unitary evolution) would, to my simple mind, solve this part of the measurement problem. I don't see the need to insist that the appearence of a mixture must be explained by the mixture being proper. In fact, in the last paper bhobba referred me to, Hensen makes it perfectly clear (section 1.2.3.) that they (case 2 and 3) are indistingishable at the level of observation since they yield the same probabilities. So I'm left asking what role is played by a proper mixed state that cannot be played by an improper one? If decoherence can provide an improper mixed state in which the observer apparently sees a particular outcome, why does this not solve the problem?

edit - Hensen's paper says that it superficially solves the outcome problem (bottom of page 39) but I don't understand the grudging "superficial". Nor the subsequent rejection of the ignorance interpretation.

 

[atyy]

I don't totally agree with bhobba's way of stating the measurement problem, but I think I understand it. What he means is that if we just have a unitarily evolving wave function, we clearly have no outcomes unless there are some additional assumptions. So the job of any interpretation that solves the measurement problem is to add assumptions that produce the outcome. For example, many worlds adds the assumption that blah, blah, blah ...

"Many worlds"? Never heard of it.

I'll put my question another way. Rather than asking how measurement creates a proper mixed state, shouldn't we ask whether it actually does so?

Why do we need outcomes at all? We know that measurements create the appearence of outcomes in the macro world, but the improper mixed state that bhobba referred to (and which does follow from unitary evolution) would, to my simple mind, solve this part of the measurement problem. I don't see the need to insist that the appearence of a mixture must be explained by the mixture being proper. In fact, in the last paper bhobba referred me to, Hensen makes it perfectly clear (section 1.2.3.) that they (case 2 and 3) are indistingishable at the level of observation since they yield the same probabilities. So I'm left asking what role is played by a proper mixed state that cannot be played by an improper one? If decoherence can provide an improper mixed state in which the observer apparently sees a particular outcome, why does this not solve the problem?

edit - Hensen's paper says that it superficially solves the outcome problem (bottom of page 39) but I don't understand the grudging "superficial". Nor the subsequent rejection of the ignorance interpretation.

Can I avoid answering the details by saying that I think I agree with your general point, and I am not totally in agreement with this way of stating the measurement problem as being only the problem of outcomes?

How would you state the measurement problem?

 

[Derek Potter]

:

Can I avoid answering the details by saying that I think I agree with your general point, and I am not totally in agreement with this way of stating the measurement problem as being only the problem of outcomes?
How would you state the measurement problem?

As Schlosshauer seems to feature highly here, I don't see the problem with using his general description:
The problem is, then, how to reconcile the vastness of the Hilbert space of possible states with the observation of a comparatively few “classical” macrosopic states, defined by having a small number of determinate and robust properties such as position and momentum. Why does the world appear classical to us, in spite of its supposed underlying quantum nature, which would, in principle, allow for arbitrary superpositions?
Key phrase here: "appear classical". I don't see the need to presuppose that it actually is classical.
Why do you ask?

 

[atyy]

: As Schlosshauer seems to feature highly here, I don't see the problem with using his general description:
The problem is, then, how to reconcile the vastness of the Hilbert space of possible states with the observation of a comparatively few “classical” macrosopic states, defined by having a small number of determinate and robust properties such as position and momentum. Why does the world appear classical to us, in spite of its supposed underlying quantum nature, which would, in principle, allow for arbitrary superpositions?
Key phrase here: "appear classical". I don't see the need to presuppose that it actually is classical.
Why do you ask?

I'm actually not fond of Schlosshauer's description. I prefer the classic how to have quantum mechanics without a fundamental status for observers. I asked because bhobba was just stating one of Schlosshauer's versions of the measurement problem, and since you were taking him to task about some detail of his version, I was wondering what yours is.

 

[Derek Potter]

I'm actually not fond of Schlosshauer's description. I prefer the classic how to have quantum mechanics without a fundamental status for observers. I asked because bhobba was just stating one of Schlosshauer's versions of the measurement problem, and since you were taking him to task about some detail of his version, I was wondering what yours is.

I don't actually see much of a difference between having QM without a fundamental status for observers and having QM with classical appearence, except that the latter would tolerate ad-hoc postulates, such as the special role of observations, and these need to be eliminated if the measurement problem is not to be trivialised. The implicit aim in both cases is to derive the projection/observer/probability postulate from the state/unitary/Hilbert postulate. Of course the former postulate may be phrased in different ways by different people so we need to make sure we are not trying to prove something that is not needed. Asserting actual collapse of a wavefunction would be overkill.

 

[VALENCIANA]

Well, we don't know where collapse of the wave function occurs. It could be at the detector, or on the more extreme side it could be consciousness. Or we may find we need to modify standard QM to allow for collapse e.g. by gravity.

By 'every object is a wave', I hope you don't mean wave in the classical sense.

 

[VALENCIANA]

What is the accepted interpretation of these two similar related issues:

1) When I am sleeping do my brain and body revert to un-collapsed wave state until and unless seen by a different observer?

2) I *never* have "seen" my brain - have the wave functions of the atoms and cells collapsed?

 

[VALENCIANA]

Do we we know what is exactly the wave function and the collapse (if there actually is a collapse) to differentiate between what happens when we are awake or asleep , or dreaming?
Is dreaming very different from reality?

 

[VALENCIANA]

What I mean is that there shouldn t be any difference between a wave function collapse in the brain and body when we are awake than when we sleep.
From an objective point of view, it should be the same.

 

[ynon]

1977ub: The accepted interpretation? Get a bunch of physicists, doctors, preachers or lawyers together and you get many so called " accepted interpretations". The state of your body or brain is not affected by someone or some thing by simply observing, visual or otherwise. Whatever state it is in is what the observer will observe. Your not having seen your brain is good but it has nothing what so ever to do with any state it may be in.Many try to apply QM behavior to the macroscopic real world events. Nope. You see a fallen tree because it had already fallen. Not visa versa. Cats are never dead and alive. Sometimes they just seem that way. Strilanc nailed it. Welcome fellow new member.

 

[Weinsyein]

Sleep physiology is not in the realm of quantum physics. Turns out, when you are asleep your brain is very active. Your "consciousness" is one of the functions of your brain. Typically, when asleep, you do not have conscious functions. ...

 

[1977ub]

1977ub: The accepted interpretation? Get a bunch of physicists, doctors, preachers or lawyers together and you get many so called " accepted interpretations". The state of your body or brain is not affected by someone or some thing by simply observing, visual or otherwise. Whatever state it is in is what the observer will observe. Your not having seen your brain is good but it has nothing what so ever to do with any state it may be in.Many try to apply QM behavior to the macroscopic real world events. Nope. You see a fallen tree because it had already fallen. Not visa versa. Cats are never dead and alive. Sometimes they just seem that way. Strilanc nailed it. Welcome fellow new member.

As helpfully commonsensical as your response is, what it does not do is address QM > Classical reality transition.
I know that some % of experts do in fact regard consciousness as causing the wavefunction collapse.
Otherwise what initiates a "measurement" ? Why does not a particle's expanding wavefunction not simply interact with the wavefunction nature of particles in the experimental apparatus without ever reducing to a particular position? I gather in MWI there is no collapse - all interactions of particle wavefunctions exist in the multiverse.

https://en.wikipedia.org/wiki/Von_Neumann–Wigner_interpretation
https://en.wikipedia.org/wiki/Measurement_problem

 

[bhobba]

Do we we know what is exactly the wave function and the collapse (if there actually is a collapse) to differentiate between what happens when we are awake or asleep , or dreaming? Is dreaming very different from reality?

Before discussing this one needs to know what a wave function is:
http://www.scottaaronson.com/democritus/lec9.html

Once you do its obvious comments like the above don't even make sense.

Its like asking if how a roulette wheel works and what number comes up depends on if you are dreaming or not - its obvious, and very obvious at that, its got nothing to do with anything.

Thanks
Bill