What is the comparison between the Born rule and thermodynamics?

[Prathyush]

Demystifier,

as one who has thought about MWI inside out. I have a question. Unitarity occurs in the interpretation where the wave function squared is the probability amplitudes and it's related to born rule. But in MWI where Born rule is difficult to be integrated.. does it mean unitarity is also in serious trouble in MWI? Or is unitarity not directly related to the born rule at all?

I think there is nothing correct about MWI.

 

[Prathyush]

Let me go back to this message where you stated that the thermodynamic thing is people attempting to explain QM in terms of classical mechanics. But in the Scientific American quote about attractor which I quoted earlier.. what if the original domain was the AsD/CFT where dynamics are analogue and it is only when stuff gets to our domain that it becomes digital or discrete or quantum? Do you consider the AsD/CFT domain as classical mechanics?

The stuff about attractors is well and good. But the point is that there is no evidence to suppose such a viewpoint could be true. Even a way to make it work probably does not exist.

I don't understand a single word you said about ads/cft.

 

[Blue Scallop]

You can have unitarity without the Born rule (e.g. in MWI), but you cannot have Born rule without the unitarity.

Ok. But does unitarity also cover entangled system (where the components don't have wave functions) or is unitarity only for pure state?

 

[Demystifier]

Ok. But does unitarity also cover entangled system (where the components don't have wave functions) or is unitarity only for pure state?

Entangled system is pure. Do you mean a subsystem of an entangled system? Subsystems do not need to evolve unitarily.

 

[Blue Scallop]

Entangled system is pure. Do you mean a subsystem of an entangled system? Subsystems do not need to evolve unitarily.

In an isolated close system that evolves unitarity, can decoherence occurs inside the isolated close system?

 

[Demystifier]

In an isolated close system that evolves unitarity, can decoherence occurs inside the isolated close system?

No.

 

[Blue Scallop]

No.

In MWI, the universe is a close system and evolves unitarity.. so how can there even be decoherence inside it?

 

[Demystifier]

In MWI, the universe is a close system and evolves unitarity.. so how can there even be decoherence inside it?

First, in MWI, it is the multiverse (not the universe) that evolves unitarily. The multiverse is the collection of all universes.
Second, decoherence happens not in the whole universe/multiverse, but in a part of it.

 

[Blue Scallop]

First, in MWI, it is the multiverse (not the universe) that evolves unitarily. The multiverse is the collection of all universes.
Second, decoherence happens not in the whole universe/multiverse, but in a part of it.

But you said decoherence couldn't occur inside a close system that evolves unitarily... this includes the subsystems.. so decoherence can't occur even in the subsystems of a close system that evolves unitarily. Our multiverse is a close system, so how can decoherence occurs in a part of it??

 

[Demystifier]

But you said decoherence couldn't occur inside a close system

I have misunderstood your question. Decoherence can happen in a subsystem of the closed system, but not in the whole closed system.

This is like saying that energy can disappear in a subsystem of the closed system, but not in the whole closed system. Would you say that energy can disappear inside the closed system?

 

[Blue Scallop]

I have misunderstood your question. Decoherence can happen in a subsystem of the closed system, but not in the whole closed system. This is like saying that energy can disappear in a subsystem of the closed system, but not in the whole closed system.

I'm reading this paper by Kastner http://philsci-archive.pitt.edu/10757/1/Einselection_and_HThm_Final.pdf

"ABSTRACT. In attempting to derive irreversible macroscopic thermodynamics from reversible
microscopic dynamics, Boltzmann inadvertently smuggled in a premise that assumed the very
irreversibility he was trying to prove: ‘molecular chaos.’ The program of ‘Einselection’
(environmentally induced superselection) within Everettian approaches faces a similar
‘Loschmidt’s Paradox’: the universe, according to the Everettian picture, is a closed system
obeying only unitary dynamics, and it therefore contains no distinguishable environmental
subsystems with the necessary ‘phase randomness’ to effect einselection of a pointer observable.
The theoretically unjustified assumption of distinguishable environmental subsystems is the
hidden premise that makes the derivation of einselection circular. In effect, it presupposes the
‘emergent’ structures from the beginning. Thus the problem of basis ambiguity remains unsolved
in Everettian interpretations."

She proposed phase randomizer was required to make decoherence become possible at all. But you said in a close system with unitarity.. decoherence could occur in the subsystem even without a phase randomization.. is she wrong?

 

[Demystifier]

But you said in a close system with unitarity.. decoherence could occur in the subsystem even without a phase randomization.. is she wrong?

Please do not imply that I said something which I didn't. I never said anything about phase randomization. And she is right.

 

[Blue Scallop]

Please do not imply that I said something which I didn't. I never said anything about phase randomization. And she is right.

I thought in a close system in unitarity evolution, there is no phase randomization? If there is phase randomization, can it still be called unitarity?

 

[Demystifier]

I thought in a close system in unitarity evolution, there is no phase randomization? If there is phase randomization, can it still be called unitarity?

If there is phase randomization, then there is no unitarity. But let me be clear. I think she is right in her critique of MWI, but I don't think that this problem should be resolved by phase randomization. I think it should be resolved by other means, most likely by introducing new "hidden" variables. In this way the theory remains unitary and the problems of MWI (that she correctly identifies) are avoided without phase randomization.

 

[Blue Scallop]

If there is phase randomization, then there is no unitarity. But let me be clear. I think she is right in her critique of MWI, but I don't think that this problem should be resolved by phase randomization. I think it should be resolved by other means, most likely by introducing new "hidden" variables. In this way the theory remains unitary and the problems of MWI (that she correctly identifies) are avoided without phase randomization.

So in a close system with unitary (or unitarity) evolution, even the subsystem shouldn't have decoherence.. right? but you mentioned decoherence can still occur in the subsystem in a unitarity evolution.. Please clarity as I'm confused what is the case. Thanks for your help.

 

[A. Neumaier]

by introducing new "hidden" variables. In this way the theory remains unitary and the problems of MWI (that she correctly identifies) are avoided without phase randomization.

This is an illusion. Classical statistical mechanics (and hence Bohmian - hidden variable - mechanics) also needs phase randomization to go from the underlying deterministic dynamics to an observed stochastic one.

 

[Demystifier]

This is an illusion. Classical statistical mechanics (and hence Bohmian - hidden variable - mechanics) also needs phase randomization to go from the underlying deterministic dynamics to an observed stochastic one.

When it comes to statistics and probability, I disagree with you almost always. What is your opinion about https://www.physicsforums.com/threads/the-sleeping-beauty-problem-any-halfers-here.916459/ ?

 

[A. Neumaier]

What is your opinion about

This is completely unrelated to the problem how to get a stochastic process from a deterministic dynamics. The latter needs some randomization assumption as it introduces irreversibility and hence an arrow of time into a reversible dynamics.

 

[Demystifier]

So in a close system with unitary (or unitarity) evolution, even the subsystem shouldn't have decoherence.. right?

Wrong. There is decoherence, but you just can't use pure MWI to explain it. What I'm saying is that pure MWI is an incomplete theory.

 

[Demystifier]

This is completely unrelated

Perhaps, but I am really curious to see how do you think on that.

 

[Blue Scallop]

Wrong. There is decoherence, but you just can't use pure MWI to explain it. What I'm saying is that pure MWI is an incomplete theory.

I think what you are saying is for example, you have a three-particle entangled system and you measure just two of them the outcomes may not show any sign of interference (in other words, suffer decoherence), you have to measure all three at once to find the correlations that demonstrate interference.

If this is true. Why can't she accept it it's natural and has to propose the particles have to become randomized before there is even a decoherence?

 

[Demystifier]

you have a three-particle entangled system and you measure just two

The "you" which performs the measurement must also be described as a subsystem of quantum particles.

 

[A. Neumaier]

Perhaps, but I am really curious to see how do you think on that.

Well, whatever she answers is correct, as it is a question about subjective probability. Subjects do not need to act rationally.

 

[Demystifier]

Well, whatever she answers is correct, as it is a question about subjective probability. Subjects do not need to act rationally.

Again, I disagree.

 

[A. Neumaier]

When it comes to statistics and probability, I disagree with you almost always.

Again, I disagree.

Disagreeing doesn't make you correct.

 

[Blue Scallop]

The "you" which performs the measurement must also be described as a subsystem of quantum particles.

I'm trying to make what you are saying relate to Kastner paper.
You seemed to be saying that decoherence can occur even without phase randomization inside a subsystem.
Reading Kastner paper again. She talked about "einselection of pointer observable".

In a natural close quantum system in unitary dynamics without phase randomization.. can einselection of pointer observable occur naturally? She seemed to be saying not. How about you?

 

[Demystifier]

Disagreeing doesn't make you correct.

Disagreeing on such basic things makes me unmotivated to discuss more complicated things on probability in physics with you.

 

[Demystifier]

You seemed to be saying that decoherence can occur even without phase randomization inside a subsystem.

Yes.

In a natural close quantum system in unitary dynamics without phase randomization.. can einselection of pointer observable occur naturally? She seemed to be saying not. How about you?

I say yes, provided that one uses a better interpretation of QM (e.g. Bohmian).

 

[Blue Scallop]

Yes.I say yes, provided that one uses a better interpretation of QM (e.g. Bohmian).

Of course Bohmian can solve it because the pointer observable is automatically position.
But let's discuss pure MWI which is more challenging.. according to Zurek Einselection rough guide paper:

"We believe that the point of view based on decoherence settles many of the questions which were left
open by MWI and CI. This includes the origin of probabilities as well as the emergence of “objective
existence”, although more needs to be done.
In particular, one issue which has been often taken for granted is looming big, as a foundation of the
whole decoherence program. It is the question of what are the “systems” which play such a crucial role in
all the discussions of the emergent classicality. This issue was raised earlier,2,28 but the progress to date has
been slow at best. Moreover, replacing “systems” with, say, “coarse grainings” does not seem to help all
— we have at least tangible evidence of the objectivity of the existence of systems, while coarse-grainings
are completely “in the eye of the observer.”Do you have any idea what he meant replacing systems with coarse grainings?

Generally. In pure MWI, it's true systems can't even be defined? really? just confirming so I'd know it's not just the thoughts of Kastner or Zurek. Thanks.

 

[Demystifier]

In pure MWI, it's true systems can't even be defined?

Yes, that's what I think.