Is MWI Self-Contradictory and Does Time Travel Need a New Approach?

[Demystifier]

If that's true. How come the detector can detect particles if only waves exist?

According to MWI, detector does not detect particles. It detects localized waves, which people like to call "particles". The localization itself is described and explained by decoherence.

 

[Varon]

According to MWI, detector does not detect particles. It detects localized waves, which people like to call "particles". The localization itself is described and explained by decoherence.

You are kidding right?

In Many worlds. I have never heard it stated that particles are localized waves (shades of Schroedinger). In MWI. Particles exist at all times.. only duplicated during split or after decoherence. What version MWI are you talking about anyway?

 

[Demystifier]

You are kidding right?

In Many worlds. I have never heard it stated that particles are localized waves (shades of Schroedinger). In MWI. Particles exist at all times.. only duplicated during split or after decoherence. What version MWI are you talking about anyway?

I believe you have seriously misunderstood something about MWI.

 

[Varon]

I believe you have seriously misunderstood something about MWI.

Ok. I'll re-read the books about it. Maybe it is because it's called a Universal
Wavefunction... but we clearly have particles... so what happened to the particles inside the wavefunction. If the wavefunction is the particle. So I am a wave function? I'll consider you not kidding. Anyway. I'll look into it.

 

[Dmitry67]

Absolutely serious.
Photon wave hits 10 megapixel digital camera matrix. It decoheres into 10 millions of states where only one cell is affected. This is what we call a 'photon'

 

[Varon]

According to MWI, detector does not detect particles. It detects localized waves, which people like to call "particles". The localization itself is described and explained by decoherence.

Ok. After preferred basis chosen, one of the eigenvalues corresponds to our world. Here an electron is a wave. We are told an electron is a point particle. So in the MWI counterpart, what is the length of the Universal Wavefunction wavelength corresponding to the electron?

 

[Varon]

Absolutely serious.
Photon wave hits 10 megapixel digital camera matrix. It decoheres into 10 millions of states where only one cell is affected. This is what we call a 'photon'

In Copenhagen, collapse chooses one of the eigenvalues which becomes a particle.

In Many worlds, after decoherence and basis chosen, one of the eigenvalues correspond to our world.

In both cases, one of the eigenvalues is chosen.

This means Copenhagen and Many worlds are equivalent in one of the eigenvalues chosen. So how come is one call a particle, the other a wave. Maybe a particle in Copenhagen is also a localize wave just like in Many Worlds?

Anyway. What is the length of the wavelenth corresponding to one of the eigenvalues in Many worlds and Copenhagen?

 

[Dmitry67]

In both cases, one of the eigenvalues is chosen.

No.
In MWI, there is a symmery between all outcomes (ignoring their probability or, how it is better to be called in MWI, "intensity of existence")
ALL outcomes exist.
This is very important.
No specific outcome is "chosen"

However, as observers remember only the past, not the future, and as they effectively lose an ability to 'communicate' with the 'other branches', all observers (in every branch) have an illusion, they 'their' outcome is the only one which exist.

 

[Dmitry67]

Ok. After preferred basis chosen, one of the eigenvalues corresponds to our world. Here an electron is a wave. We are told an electron is a point particle. So in the MWI counterpart, what is the length of the Universal Wavefunction wavelength corresponding to the electron?

The same as in QM.
MWI is a 'pure' QM - MWI does not have any additional assumptions, on the contrary, it is a claim that no additional assumptions are needed.

 

[Varon]

No.
In MWI, there is a symmery between all outcomes (ignoring their probability or, how it is better to be called in MWI, "intensity of existence")
ALL outcomes exist.
This is very important.
No specific outcome is "chosen"

However, as observers remember only the past, not the future, and as they effectively lose an ability to 'communicate' with the 'other branches', all observers (in every branch) have an illusion, they 'their' outcome is the only one which exist.

I know. It's just a bad choice of words when I said one of the eigenvalues is chosen. What I meant was our branch only experience one of the eigenvalues and all outcomes exist. Since all are wave, I'm asking what is the wavelength of the particle in this sense. So it's the same de Broglie wavelength? But this is based on wavelengh = h/momentum. Is there another formula that only inputs the particle existence without regards to momentum?

 

[Varon]

If Many worlds has only wave function and no particles. Why didn't Schroedinger discovered it? He spent a lifetime believing only wavefunction exist, what makes him fail to propose the Many worlds where there are only waves?

Back in the 1920s when Schroedinger thought it's all waves and no particles. Henrik Lorentz made him realized that wavepacket spreads. Lorentz told Schroedinger "Wave packet will spread with time and your idea of representing particles completely in terms of the superposition of waves is invalid"

Now what I want to know is how is this wave packet spreading related to one of the eigenvalues (let's avoid Many worlds in this question to avoid complication).

 

[Dmitry67]

I know. It's just a bad choice of words when I said one of the eigenvalues is chosen. What I meant was our branch only experience one of the eigenvalues and all outcomes exist. Since all are wave, I'm asking what is the wavelength of the particle in this sense. So it's the same de Broglie wavelength? But this is based on wavelengh = h/momentum. Is there another formula that only inputs the particle existence without regards to momentum?

Why do you think that it should be different in MWI from what QM tells us? Note that the wavelength of particle has nothing to do with how small detector can be. For example, famous 21cm hydrogen line can excite hydgogen atoms which are 10-8cm in size. If we have a 'matrix' with step of 0.001cm, made of such atoms, we would see a 0.000001cm^2 'dot', created by 21cm lightwave (these results will be true in any Int, of course).

 

[Dmitry67]

If Many worlds has only wave function and no particles. Why didn't Schroedinger discovered it? He spent a lifetime believing only wavefunction exist, what makes him fail to propose the Many worlds where there are only waves?

Back in the 1920s when Schroedinger thought it's all waves and no particles. Henrik Lorentz made him realized that wavepacket spreads. Lorentz told Schroedinger "Wave packet will spread with time and your idea of representing particles completely in terms of the superposition of waves is invalid"

Now what I want to know is how is this wave packet spreading related to one of the eigenvalues (let's avoid Many worlds in this question to avoid complication).

I think there were 2 major reasons.
1. The idea was too crazy - they already had enough crazyness to deal with;
2. In the beginning of 20th century, there was a gap separating macro and micro, huge gap separating 'measurement devices' from QM. So there was a hope that QM weirdness would somehow 'fade' when approaching the macroscopic scale. Like how Bohr showed earlier in his model how Qm levels in atom transform into continuum of states on bigger scales.

 

[Varon]

I think there were 2 major reasons.
1. The idea was too crazy - they already had enough crazyness to deal with;
2. In the beginning of 20th century, there was a gap separating macro and micro, huge gap separating 'measurement devices' from QM. So there was a hope that QM weirdness would somehow 'fade' when approaching the macroscopic scale. Like how Bohr showed earlier in his model how Qm levels in atom transform into continuum of states on bigger scales.

You prefer MWI because of the collapse postulate seems to make the deterministic wave function inconsistent. It is not. Here comes the magic of the observers (either particles sensing other particles or bigger environment or system). It has got to do with Information Theory and information exchange between the quantum. This is actually quite elegant. Fra has even formulated almost a complete theory of it. Try it before delving into the MWI schizophenia. What's your criticism of Fra appraoch? (Note: Fra is the one without the Wolverine icon)

 

[Demystifier]

Maybe a particle in Copenhagen is also a localize wave just like in Many Worlds?

Yes. In fact, the only (relatively well-known) interpretation of QM in which "particles" really are particles - is the Bohmian interpretation.

 

[Demystifier]

If Many worlds has only wave function and no particles. Why didn't Schroedinger discovered it?

Because he did not understood the mechanism of wave-function splitting (now well understood through decoherence).

 

[Varon]

Because he did not understood the mechanism of wave-function splitting (now well understood through decoherence).

Any idea how to connect MWI with quantum field theory and particle physics?

 

[Fyzix]

Because he did not understood the mechanism of wave-function splitting (now well understood through decoherence).

It must be said that assuming wavefunction is real and all there is + decoherence does not give you many worlds.

The Bare Theory, which assumes this alone is not a many world interpretation.

Mitchell Porter also touches on this:

http://lesswrong.com/lw/19s/why_manyworlds_is_not_the_rationally_favored


Side note:
I'm pretty sure I read somewhere that Schroedinger realized MWI did not work because of botn probability and the fact that it would violate relativity.
Unfortunately I can't find the source of this claim right now.

 

[Demystifier]

Any idea how to connect MWI with quantum field theory and particle physics?

Why do you think there would be a problem?

 

[Varon]

Why do you think there would be a problem?

Many worlds are classical theory. When you have interacting fields and particles like quantum field theory.. i wonder how you could mix Many worlds in them. Has anyone tried modeling how Many worlds would appear in quantum field theory and whether it would still give the same experimental results and predictions? Most would state that since QM works in QFT, Many worlds should work too.. but it's a classical model. Won't you have trouble when you embed it into QFT or gauge theory?

 

[Demystifier]

Many worlds are classical theory. When you have interacting fields and particles like quantum field theory.. i wonder how you could mix Many worlds in them. Has anyone tried modeling how Many worlds would appear in quantum field theory and whether it would still give the same experimental results and predictions? Most would state that since QM works in QFT, Many worlds should work too.. but it's a classical model. Won't you have trouble when you embed it into QFT or gauge theory?

If you think of many worlds as a "classical theory", then you can extend the whole idea to a many world "classical theory" of QFT. In this theory, neither particles nor fields exist. What exists are certain generalized wave functions which depend on an infinite number of variables.

 

[Dmitry67]

I'm pretty sure I read somewhere that Schroedinger realized MWI did not work because of botn probability and the fact that it would violate relativity.
Unfortunately I can't find the source of this claim right now.

Note:

Fyzix fights some weird flavor of MWI, which is not based on pure unitary evolution, but adds some weird stuff about 'spacetime unzipping' or 'hard, definite and final world splitting'. Then he attacks MWI based on the fact, that the equation for the fictious 'border', which separates different 'worlds' is non covariant.

There is a good quote from Everett FAQ "The concept of "world" in the MWI is not a rigorously defined mathematical entity, but a term defined by us (sentient beings) in describing our experience".

 

[Dmitry67]

Note 2:

MWI is a 'bare theory' as is explicitly stated in wiki article:
http://en.wikipedia.org/wiki/Many-worlds_interpretation

MWI is distinguished by two qualities: it assumes realism,[16][17] which it assigns to the wavefunction, and it has the minimal formal structure possible, rejecting any hidden variables, quantum potential, any form of a collapse postulate (i.e., Copenhagenism) or mental postulates (such as the many-minds interpretation makes).

This quote also explains that if someone talks about 'hard picture of spacetime unzipping' etc - then it is not MWI.

 

[Fyzix]

No, I've already informed you that the Everett-DeWitt account of MWI requires violation of relativity.

And now I find myself ONCE AGAIN informing you about your favorite interpretation: BARE/PURE wavefunction realism yields BARE THEORY read Jeffrey Barrett or David Albert on this subject.

You got your own warped MWI where doctors collapse worlds, so stop talking as if you understand what you are talking about and everyone else is wrong.

 

[Dmitry67]

No, I've already informed you that the Everett-DeWitt account of MWI requires violation of relativity.

Informed about your opinion? Yes
provided any useful info?
We had only one quote about "unzipping the spacetime".
As there is no "unzipping" there is nothing we can discuss.
Do you have anything else?

From another side, as unitary evolution is covariant, MWI *must* be covariant. You did not reply to that either.

For the commonly accepted definitions of flavors of theories, I insist on using WIKI. One can publish an article claiming "here is MY understanding of MWI and only it is true!".And you will be positng that link from arxiv as a "proof". So please provide a WIKI prooflink for the definition of the BARE theory.

 

[Fyzix]

Informed about your opinion? Yes
provided any useful info?
We had only one quote about "unzipping the spacetime".
As there is no "unzipping" there is nothing we can discuss.
Do you have anything else?

From another side, as unitary evolution is covariant, MWI *must* be covariant. You did not reply to that either.

I have written probably 5 pages of information to you, when you have not comprehended the information, I have RE-written it.
When you have argued back, I have thought about it and even inquired others about it to give you as easy to understand explanatino as possible, after doing this 50 times, I have given up.
You believe in MWI because it is infact your religion.
You ignore EVERY obstacle MWI faces because like you said your self "I WOULD BE DEVASTATED IF MWI ISNT TRUE".
You have also admitted here on this forum several times that all problems will be solved by some futuristic theory of consciousness.

When you are willing to take such leaps of faith to defend a flawed hypothesis it is obvious(atleast to me) that a discussion with you will only be a waste of time.
Remember, your view of MWI is wrong.
Whether you go to the doctor or not, will not put you in a branch where you have a tumor or not, THIS IS what you are saying about MWI, this is so far removed, even from the Deutsch-Wallace approach, so yes, there is no way I can argue against your arguments because you have your own MWI interpretation and consciousnes theory that has nothing to do with reality.

 

[Fyzix]

And please don't lie again and say I don't give you sources.

I have quoted way more than just the stanford entry on Everett by Barrett.

 

[Dmitry67]

I have written probably 5 pages of information to you, when you have not comprehended the information, I have RE-written it.
When you have argued back, I have thought about it and even inquired others about it to give you as easy to understand explanatino as possible, after doing this 50 times, I have given up.
You believe in MWI because it is infact your religion.
You ignore EVERY obstacle MWI faces because like you said your self "I WOULD BE DEVASTATED IF MWI ISNT TRUE".
You have also admitted here on this forum several times that all problems will be solved by some futuristic theory of consciousness.

When you are willing to take such leaps of faith to defend a flawed hypothesis it is obvious(atleast to me) that a discussion with you will only be a waste of time.
Remember, your view of MWI is wrong.

I have admitted that it would be sad for me if MWI was false; however, I would accept the result if there would be proof. So it isn't a religion. You had asked me about it, and I had explicitly said that. Why are you giving false statements about what I have said? Do you need me to go thru my Sent box and give you the exact quotes?

The 5 pages you provided was similar to what you had said above, "clearly it is wrong" or "MWI has severe problems with relativity" or "there are tons of articles about...". It is like saying "you are wrong... no you are wrong..."

I tried to focus on something specific: compatibility of MWI with SR. Once again, you did not reply. Fyzix, this is simple: if unitary evolution is covariant, and MWI does not have any additional assumptions, then it is compatible with SR. If you have any additional assumptions, you should state them clearly before making conclusions.

When I ask to discuss it step by step, you switch discussion to other subjects, just to paphosly repeat the same claim "MWI has severe problems with relativity!" when new audience come into thread.

Are you ready to discuss this small subject (MWI and SR) and go thru it - step by step?

 

[Dmitry67]

UPD:
I decided that it is not scietific to discuss the emotional component or PM here. If you want to ask anything about our discussion in PM - send PM.

Here I will discuss *only* the technical stuff - if you are ready to discuss the MWI vs SR.

 

[Fyzix]

Dmitry67:

I have already told you that the Many Worlds account by Everett & DeWitt was incompitable with special relativity.
I never said that Deutsch-Wallace approach had the same problem!
So why are you bringing tihs up now?!

Because I said earlier in the thread that Schroedinger figured out there was a problem with probability and relativity when thinking of the wavefunction as real?
THIS IS TRUE!
Because Schroedinger was trying to make a bare theory where ontology actually existed!
Tim Maudlin brought this historical bit to my attention, but if you google it with Maudlin's name, I'm sure you can find it too.
I brought that up to inform Varon about history and why Schroedinger believed what he believed, not because we were arguing the DeutschWallace approach!


Now have you bothered to read up on Bare Theory?