Is the wavefunction subjective? How?

[jlcd]

Yep. Which makes it out of scope for discussion unless you can give a specific reference.
Please give a reference.

It's in last page of Zurek paper:
https://arxiv.org/pdf/1412.5206.pdf
Say. Can Many worlds without the other worlds (even in formalism like Objective Collapse) really describe the interactions of objects (like an atom) or does it still need a more complete description just like case 1 where wave function is subjective?

 

[PeterDonis]

Many worlds without the other worlds

What does this mean?

 

[jlcd]

What does this mean?

In the paper, Zurek said "There is no need to attribute reality to all the branches. Quantum states are part information.". Meaning the other worlds are not really there. I think Zurek needs new physics to overcome unitarity. Also I think atyy mentioned something about BM is many worlds without the worlds.

Whatever, let's take first the original Many worlds. If all the worlds were real (I know they were caused by entanglement processes as you described many times.. I'm aware of the distinctions). This is enough to describe how atoms interact or how objects interact? Or there is still something missing or incomplete description? Then what is the advantage of this over Bohr subjective wave function that still require more complete descriptions?

 

[PeterDonis]

In the paper, Zurek said "There is no need to attribute reality to all the branches.

He's not talking about any version of many worlds when he says that.

If all the worlds were real (I know they were caused by entanglement processes as you described many times.. I'm aware of the distinctions). This is enough to describe how atoms interact or how objects interact?

Sure, if you define "how atoms interact" or "how objects interact" to include the existence of all of the many worlds.

 

[jlcd]

He's not talking about any version of many worlds when he says that.
Sure, if you define "how atoms interact" or "how objects interact" to include the existence of all of the many worlds.

Ok. The eigenstates from entangled processes as you described in previous messages form worlds. But I don't really like it. This was why I was exploring Zurek version all are information only. Either this or back to Born wave function as subjective.. then needs a whole new theory for the complete description. Either seems hard but that's physics. Any researchers like Zurek who is exploring the state is some kind of information only? like Wheeler It from Bit.

Oh i didnt finish the article by Lubos mentioned by the OP where he critiqued Neumaier. Ill finish reading the article later and maybe ask about it so not off topic.

 

[jlcd]

Neither one involves any relativistic effects, so no.

I understand in the LHC where particles are moving close to the speed of light. Relativistic effects are very obvious and QFT is required. But is it not in normal atom even how excited states of the electron emit a photon need QFT treatment? So not just relativistic effects? Anyway. I finished Lubos Motl many articles linked in the OP. So the bottom line is :

"Instead of specifying observables (linear operators on the Hilbert space) and calculating their eigenvalues and their probabilities of individual eigenvalues given some knowledge about the state, they keep on asking whether some "cloud here" affects another "cloud there" or whether it "collapses", assuming that the clouds objectively exist in the classical sense. That's not a good starting point to understand the essence of modern physics."

Lubos is very authorative. Right now. I wonder how large in percentage of physicists hold that view. I was so exposed to Zurek, Demystifier, Neumaier etc. views over the years I tend to ignore Lubos views which may still be the majority?

To clarify your own article when you commented "But if we take that idea to its logical conclusion, it implies that QM must be an incomplete theory; there ought to be some more complete description of the system that fills in the gaps and allows us to do better than merely probabilistic predictions."

Reference https://www.physicsforums.com/insights/fundamental-difference-interpretations-quantum-mechanics/

Let's take the double slit experiments. Lubos seemed to be emphasizing we must only focus on the output and not how the the one electron at a time version can interfere with itself. So does your "more complete description" just involved *trying* to figure out how the one electron behave when it is in between the emitter and detector or did you mean something else by "more complete description"?

And for the questions how it *interact* in Lubos or orthodox view, the answer is that it is emitted in the emitter and just appear in the detector. No interaction. Period"?

 

[PeterDonis]

is it not in normal atom even how excited states of the electron emit a photon need QFT treatment? So not just relativistic effects?

Whether you need QFT to analyze photon emission by excited states of atoms depends on how precise you want to be. A non-relativistic approximation is fine if you don't care about things like the Lamb shift.

 

[jlcd]

In msg number 79 of the thread (closed from one year of inactivity) https://www.physicsforums.com/threa...s-of-quantum-mechanics-comments.936506/page-4 you commented something I want to further inquire but can't reply there anymore so allow me to ask this here:

A better way of asking the question you might be trying to ask is, do people care about case 1 vs. case 2 because of the different ways the two cases suggest of looking for a more comprehensive theory of which our current QM would be a special case? The answer to that is yes; case 1 interpretations suggest different possibilities to pursue for a more comprehensive theory than case 2 interpretations do. Such a more comprehensive theory would indeed make different predictions from standard QM for some experiments. But the interpretations themselves are not the more comprehensive theories; they make the same predictions as standard QM, because they are standard QM, not some more comprehensive theory.

I'm aware one must draw the key distinction between interpretations of an existing theory, standard QM, and more comprehensive theories that include standard QM as a special case.

My interest in QM is towards these more comprehensive theories.

But then in the history of physics. The weak force, the strong force and EM were discovered even without upgrading QM. So even if there were another force of nature. It won't necessarily required alterations of QM. But Smolin and even Neumaier hinted quantum gravity may require more understanding of the foundation of QM.

Now let focus on these statements of yours :"case 1 interpretations suggest different possibilities to pursue for a more comprehensive theory than case 2 interpretations do. Such a more comprehensive theory would indeed make different predictions from standard QM for some experiments".

Do you have any examples in mind?

If not. Let me give an example (for sake of theoretical understanding and discussions). If someone can demonstrate a physical object like marble can be made to disappear and reappear elsewhere. Does it differentiate between case 1 and case 2? Because case 1 which just focus on the statistics of the output (the observable) is silent on what's in between and also silent on any mechanism making the entire object disappear. So if someone can demonstrate it. It can refute case 1, right? Or can one argue that is it part of the more complete description of case 1? This is very important question. There are many things Witten, Smolin, Hossenfelder and great giants of physics didn't have access to in this world. And this is a categorical statement that can be proven. But then this is just an example remember. If you can give examples about how say case 1 interpretations suggest different possibilities to pursue, please give it so I don't have to mention seemingly silly examples to get a grip of your thoughts of how case 1 or case 2 can give different possibilities of more comprehensive theories to pursue.

 

[PeterDonis]

My interest in QM is towards these more comprehensive theories.

And at this point we're getting into personal speculation, which is off limits for PF discussion.

Thread closed.