The Refutation of Bohmian Mechanics

Misericorde

This is the exact means by which it has "tapdanced" Varon; it keeps adding to the problem without solving anything. Instead of wave-particle duality you have a pilot wave. Position is preferred, MWI is implied, and so on, and this is all on top of the formalism.

I'd say:

It's deBB that's 1, Formalism that's 0, and MWI is somewhere in between.

Dmitry67

Varon, I know there are some attempts to derive the Born rule in MWI, so far I think they are far from being final. In any case, I hope an appearence of the Born rule is emergent somehow on the macroscopic level or on conscious level.

I *almost* share Many Minds view: yes, no 'measurement devices' observe anything: they just transfer the decoherence. Photon is decoherenced with the photosensor, it transfers it to the hand of the voltmeter, photons transfer that information to our retina. All elements of that chain can be in superposition, and the only final and ultimate agent for the observation is our consciousness. Superposition ends not when it is measured (it just puts measurement device in a correlated superposition), it ends when we see it, when we feel it.

World is a very strange place, there is no preferred basis physically, but there are some special ones of the systems with qualia. However, to extract a system from the environment, we need a basis, so it is recursive. Ultimately, Born rule can be also an illusion, created by our consicousness, like the moment NOW.

However, I believe that consicousness can be physically studied (to some extent) so Many Minds should not have any additional assumtions - everything must be derived from pure MWI.

Dmitry67

I had also attacked dBB based on that
Demystifier's response was, if I remember it correctly, that the opposite to knowing position exactly is knowing the momentum exactly. Then position is not localized at all. But in the Universe there are no global frames.

Varon

What I can't understand in this Many Worlds is what if the observers are machines or video camera in a laboratory experiment system without humans. What would serve as Many Minds then? Or would it be invalid? What difference if humans observe them versus automated machines? Random choice? But we could design machine that can initiate random choice too. Pls. elaborate.

Misericorde

I agree with your view; I've never understood why deBB is taken as even remotely mainstream. Your point about MWI and Occam's Razor is enough for me frankly.

Demystifier

I have already answered it in post #188.

Dmitry67

This is why I said I *ALMOST* accept Many Minds, but I am still on MWI ground.
Unitary evolution is objective, so when room is isolated from the environment, there is no difference if there are any consious beings inside. But until someone conscious had opened the door, there is simply no basis to be used... well, you can use any basis, but results will be different for each one, and there is no rule to favor one versus the other.

Mathematically we can use ANY basis, but consciousness breaks the symmetry between all possible ones, dividing them into 2 categories: those who feel and the dead and arbitrary ones. As our experience is limited to a very narrow subset of them, we make an extremely 'unfair sampling' of nature. Just for example, pick any random point in cosmos. With 99.99999999999999% probability it will be intergallatic void. But we never experience such places!

For some reason consciousness can break the symmetry between all possible basis, like it breaks the symmetry of time, dividing it into future, past and now. Interestingly enough, the special role of the moment called NOW is denied by the modern Block Time approach, so "flow of time" and "NOW" are called illusions, created by our consciousness. I agree, but what other notions we got used to are also just illusions?

So here is my answer: I don't believe that consciousness affects the physical processes or plays a special role in the evolution of the Universe. Universe does not care about consciousness. However, conciousness is responsible for an unfair sampling of the observations, put to the extreme.

Demystifier

Very interesting hypothesis. Of course, I'm not asking for a proof, but can you at least give some arguments which would make it a bit more plausible?

Dmitry67

I had provided one (about intergalactic void). Of course, you can call it AP, but AP is usually used in a narrower sense - for the selection of initial conditions, like the parameters of the standard model.

I always wanted to share one crazy thought. May be now it is time. It is an indirect, not a direct argument for what I had said above, and I don't claim that it is true; but it can show how deep the rabbit hole can go.

************

I use MWI framework. There are all sorts of branches: with higher 'probability', and with tiny probability. There are even branches where some absurd laws are respected, for example, Uranium atom decay faster on Saturdays. Lets call such 'law' a meta-law (as it is not fundamental and can't be derived, in principle, from QM)

Let's call the branches where meta-laws exist 'meta-branches'. Now assume that physical laws of our world are not 'enough' for the consciousness to exist. However, when some very special meta-laws are plugged in, consciousness is possible.

In such case, only meta-branches would be observed (no matter how tiny their probability is), and the fundamental laws can be very different from what we tend to think. Am I crazy?

Misericorde

I don't think that's crazy, just not verifiable; it's a natural if exotic philosophical extension of existing concepts. I enjoy your view, although I don't share it, while we're playing with the notion of MWI why not explore the exotic probabilities? In some ways, your idea emphasizes for me why MWI and all interpretations fall short, because they can be taken to extremes so far beyond what physics is even designed to answer or probe.

Dmitry67

Another (purely emotional) argument against dBB.

Look at SR/GR and QM as 'steps' toward the truth. Every major step was more and more contre-intuitive, and "common sense reasoning" had less and less value. Even MWI is not technically a new 'step', it perfectly fits that scheme. On the contrary, dBB looks so 'human made', artificial - return to the old good billiard ball physics. Soooo comfortable for our common sense reasoning... This is why I think it can't be true...

Demystifier

No, you are just not specific enough.

Dmitry67

I don't claim it is true, I am just showing a range of theories MWI/QM can be 'compatible' with.

P.S
I have a question for you about dBB. I remember once there was a discussion about Bell/EPR and no-conspiracy assumption. You replied that you don't see an exact difference between superdeterminism and no-conspiracy. I was thinking about it, I believe I can tell what the difference is.

Conspiracy is some set of boundary conditions, defined at Universe time t>0. Such boundary conditions can be very simple (that area is void at that time) or complicated so you have to write a complicated function to evaluate if it is true (whenever EPR experiment is performed, the results should yeild the specific condition...). Details are not important, the only important thing is that the boundary condition is defined for regions of spacetime at t>0.

Another word for Conspiracy is Destiny.

Q: Do you believe that in dBB there are no boundary conditions defined at Universe time t>0? So do you claim that ALL boundary conditions of dBB are defined strictly at t=0? (Big bang?)

Demystifier

Your questions require a careful answer:
I believe in nonrelativistic BM all initial conditions are specified at the same time t, but not necessarily at t=0. And I don't see any conspiracy in it.

Ilja

My main objection against MWI is that it needs, in fact, some additional structure: It clearly needs some subdivision of the universe into subsystems. But there is nothing in the universe which could be used as a natural candidate. The subsystems we observe in everyday life, and which are also widely used in examples and discussions, like, in particular, minds, clearly do not have the fundamental character which would be necessary - they exist only in states of the universe which are extremely close to our actual state. What is my state in a universe where the Earth does not even exist? A nonsensical question.

But this vague subdivision into subsystems is an additional structure which is not necessary in dBB. It also needs additional structure, but of a different type, the one into configuration and momentum. That's a subdivision which is fundamental already in classical mechanics. It shows up in the equations: H=p^2/2m + V(q), quadratic in momentum but not in the configuration variables, a property which survives even for some relativistic fields, and there is no known system where such a subdivision would be problematic.

mfb

The subdivision occurs naturally as evolution of the wave function. This is called decoherence.
If you just take a wave function and unitary evolution, you directly arrive at MWI. You get the branching structure in all (relevant) chaotic systems. If you do not "want" those branches, you have to add a structure - collapses (e.g. Copenhagen), particles (dBB) or something else.

Ilja

Sorry, but no, there is nothing natural there. You need an additional structure - a subdivision of the universe into subsystems. Only if you assume such a subdivision as given, you obtain all the other things, like branching and so on.

No. You also need additional structure in MWI - the subdivision of the universe into subsystems.