How I Stopped Worrying and Learned to Love Orthodox Quantum Mechanics - Comments

[Demystifier]

if I have to buy just one book.. which of the following is good:
https://www.amazon.com/dp/3642179738/?tag=pfamazon01-20
https://www.amazon.com/Trajectory-Description-Quantum-Processes-Fundamentals/dp/3642180914/257-7565493-7958461?_encoding=UTF8&*Version*=1&*entries*=0&portal-device-attributes=desktop
https://www.amazon.com/dp/0387229647/?tag=pfamazon01-20

I am not an expert for applications of BM as a computational tool, but I think the Wyatt's book is the best.

 

[Demystifier]

My question is about Copenhagen. Is Sabine right that it is about "I don't care if the cat is dead"?

This is only one of version of Copenhagen. For other versions see https://arxiv.org/abs/1703.08341 Sec. 2.1.

 

[Fra]

I might have more comments later but i seem to never get enough time...until then:

I just wanted to applaud Demystifier not letting what is not conceptually satisfactory pass!

The thing that bothered me was how could Nature work like that? How could that possibly be? What could be a possible physical mechanism behind the abstract rules of QM? Should one conclude that there is no mechanism at all and that standard QM (including QFT) is the end of story?

I feel exactly the same way, even though my hypothesis may lie in a different direction. Power to you for not swallowing what is really substandard reasoning, and not loosing focus! That in an environment where it is a fact that "most people" seem to ignore these things probably for pragmatic reasons. I have found this extremely disturbing.

Thanks for sharing your journey!

/Fredrik

 

[AlexCaledin]

And the https://en.wikipedia.org/wiki/Hidden-measurements_interpretation seems saying "Cat knows, ask him..."

 

[Demystifier]

And the https://en.wikipedia.org/wiki/Hidden-measurements_interpretation seems saying "Cat knows, ask him..."

Asking cat does not help much: https://arxiv.org/abs/1406.3221

 

[Fra]

It seems, but we don't know if this persists at even smaller distances than available by current experimental technology. The default hypothesis is that it persists, but a hypothesis that it doesn't is also legitimate and Bohmian mechanics is not the only motivation for such a "heretic" hypothesis. See e.g. Horava gravity.

As before, i have a different angle but i agree to this 100%

My default hypothesis is that lorentz invarance (and spacetime itself for that matter) are indeed emergent at lower(but still high) energies. I think that at very high energies causality become more stochastic and the arrow of time get more and more uncertain and thus lorentz symmetry loose its meaning.

Thus any no-go claims as to what isn't possible based on extrapolating lorentz invariance to infinity might in fact misguide us.

/Fredrik

 

[Demystifier]

My recent paper "Bohmian mechanics for instrumentalists" linked in my signature below is a sort of an elaborated version of the insight at the beginning of this thread.

 

[DennisN]

Demystifier submitted a new PF Insights post

@Demystifier, I did not read your article until today, thank you for a very interesting account! And an extra thumbs up from me for the very funny title!

 

[haushofer]

I only read it today too, and as someone who is also fascinated by the Bohmian interpretation (but only acquinted with it at a superficial level), I enjoyed it thoroughly. Many thanks.

 

[Auto-Didact]

I am not an expert for applications of BM as a computational tool, but I think the Wyatt's book is the best.

Agreed here. Even from a purely mathematical PDE point of view, the striking similarity between QM and hydrodynamics, i.e. the so-called quantum hydrodynamics, absolutely fascinates me. A mathematical physicist by the name of R. Carroll rejoins in this fascination, quoted here.

What is your opinion of the hydrodynamic formulation?

 

[Demystifier]

What is your opinion of the hydrodynamic formulation?

I think it cannot explain why the unique measuremenet outcomes appear. For instance, in the two-slit experiment with a single photon, why do we detect photon at a single position only?

 

[vanhees71]

I am not an expert for applications of BM as a computational tool, but I think the Wyatt's book is the best.

In which sense is BM a "computational tool"? It only adds the trajectories a posteriori when the wave function is calculated from "conventional QT". I always considered BM as just an alternative deterministic non-local interpretation of non-relativistic QT but not that one can establish some practical calculational tools using it.

 

[Demystifier]

In which sense is BM a "computational tool"? It only adds the trajectories a posteriori when the wave function is calculated from "conventional QT".

There is a way to compute trajectories first and then to infer the wave function from it. See e.g. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.82.5190

 

[martinbn]

My recent paper "Bohmian mechanics for instrumentalists" linked in my signature below is a sort of an elaborated version of the insight at the beginning of this thread.

My problem with your signature is that it seems that there is quite a bit of wishful thinking motivated only by the desire that BM is the true description of the world.

 

[Demystifier]

My problem with your signature is that it seems that there is quite a bit of wishful thinking motivated only by the desire that BM is the true description of the world.

You may call it wishful thinking, I call it physical hypothesis motivated by physical intuition based on BM. In a sense, any scientific hypothesis can be thought of as wishful thinking, but it doesn't make the hypothesis less scientific. The 19th century hypothesis that matter is made of atoms was also an example of "wishful thinking".

“The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.”
― George Bernard Shaw

 

[martinbn]

Not sure if Shaw meant physics, I suspect that by the world he probably meant society.

You may call it wishful thinking, I call it physical hypothesis motivated by physical intuition based on BM. In a sense, any scientific hypothesis can be thought of as wishful thinking, but it doesn't make the hypothesis less scientific. The 19th century hypothesis that matter is made of atoms was also an example of "wishful thinking".

The way your proposal looks to me, in line of your example, is as someone proposing that atoms don't exist and it only appears that way. And he suggests that based on his favorite model.

 

[Auto-Didact]

I think it cannot explain why the unique measuremenet outcomes appear. For instance, in the two-slit experiment with a single photon, why do we detect photon at a single position only?

The mathematical reason for unique measurement outcomes in single particle wavefunctions is due to the non-local nature of the system i.e. the presence of some cohomology element $\eta$: for any sufficiently small open subregion $G'$ of a region $G$, the cohomology element $\eta$ vanishes when restricted down to $G'$. See this thread for elaboration and/or further discussion.

In either case, the hydrodynamic formulation doesn't specifically set out to answer such a question in the first place, even though it might be able to if one would select the correct nonlinear PDE to generalize towards which naturally contains such non-local properties.

Excuse me, I should have clarified earlier; I meant what is your opinion on the mathematical physics (as explained here) of the hydrodynamic formulation of QM? Do you view such mathematical work as pure baseless numerology? I get the feeling many theoretical physicists do.

For more background, here is a recent survey article by fluid dynamicist John Bush (MIT, Applied Math), primarily described in section 4 and 5 (feel free to skip section 1-3, if you are already familiar with it and/or like me not necessarily so much interested in experimental analogues): Pilot Wave Hydrodynamics.

 

[Auto-Didact]

My problem with your signature is that it seems that there is quite a bit of wishful thinking motivated only by the desire that BM is the true description of the world.

"The supreme task of the physicist is to arrive at those universal elementary laws from which the cosmos can be built up by pure deduction. There is no logical path to these laws; only intuition, resting on sympathetic understanding of experience, can reach them. In this methodological uncertainty, one might suppose that there were any number of possible systems of theoretical physics all equally well justified; and this opinion is no doubt correct, theoretically. But the development of physics has shown that at any given moment, out of all conceivable constructions, a single one has always proved itself decidedly superior to all the rest."
- Einstein

You may call it wishful thinking, I call it physical hypothesis motivated by physical intuition based on BM. In a sense, any scientific hypothesis can be thought of as wishful thinking, but it doesn't make the hypothesis less scientific. The 19th century hypothesis that matter is made of atoms was also an example of "wishful thinking".

“The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.”
― George Bernard Shaw

"Long may Louis de Broglie continue to inspire those who suspect that what is proved by impossibility proofs is lack of imagination."
- John Stewart Bell

Not sure if Shaw meant physics, I suspect that by the world he probably meant society.

The way your proposal looks to me, in line of your example, is as someone proposing that atoms don't exist and it only appears that way. And he suggests that based on his favorite model.

"One should not reproach the theorist who undertakes such a task by calling him a fantast; instead, one must allow him his fantasizing, since for him there is no other way to his goal whatsoever. Indeed, it is no planless fantasizing, but rather a search for the logically simplest possibilities and their consequences."
- Einstein