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aaronsw comments on Should I believe what the SIAI claims? - Less Wrong
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I have not read the MWI sequence yet, but if the argument is that MWI is simpler than collapse, isn't Bohm even simpler than MWI?
(The best argument against Bohm I can find on LW is a brief comment that claims it implies MWI, but I don't understand how and there doesn't seem to be much else on the Web making that case.)
MWI just calculates the wavefunction.
Copenhagen calculates the wavefunction but then has additional rules saying when some of the branches collapse.
Bohm calculates the wavefunction and then says that particles have single positions but are guided by the wavefunction.
But MWI doesn't get the right calculation in terms of probability
Good point. I'd say that it doesn't have any calculation of the probability. But some people hope that the probabilities can be derived from just MW. If they achieve this then it would be the simplest theory. But if they need extra hypotheses then it will gain complexity, and may well come out worse than Bohm.
Mitchell_Porter makes the case, but reading him makes my brain shut down for lack of coherence. I assume Yudkowsky doesn't favor Bohm because it requires non-local hidden variables. Non-local theories are unexpected in physics, and local hidden variables don't exist.
There's more to Bohmian mechanics than you may think. There are actually observables whose expectation values correspond to the Bohmian trajectories - "weak-valued" position measurements. This is a mathematical fact that ought to mean something, but I don't know what. Also, you can eliminate the pilot wave from Bohmian mechanics. If you start with a particular choice of universal wavefunction, that will be equivalent to adding a particular nonlocal potential to a classical equation of motion. That nonlocal potential might be the product of a holographic transformation away from the true fundamental degrees of freedom, or it might approximate the nonlocal correlations induced by planck-scale time loops in the spacetime manifold.
I have never found the time or the energy to do my own quantum sequence, so perhaps it's my fault if I'm hard to understand. The impression of incoherence may also arise from the fact that I put out lots and lots of ideas. There are a lot of possibilities. But if you want an overall opinion on QM which you wish to be able to attribute to me, here it is:
The explanation of QM might be "Bohm", "Everett", "Cramer", "'t Hooft", or "None of the Above". By "Bohm", I don't just mean Bohmian mechanics, I mean lines of investigation arising from Bohmian mechanics, like the ones I just described. The other names in quotes should be interpreted similarly.
Also, we are not in a position to say that one of these five approaches is clearly favored over the others. The first four are all lines of investigation with fundamental questions unanswered and fundamental issues unresolved, and yet they are the best specific proposals that we have (unless I missed one). It's reasonable for a person to prefer one type of model, but in the current state of knowledge any such preference is necessarily superficial, and very liable to be changed by new information.
Well, that's understandable. Not everyone has all the free time in the world to write sequences.
That's exactly what I wish Yudkowsky's argument in the QM sequence would have been, but for some reason he felt the need to forever crush the hopes and dreams of the people clinging to alternative interpretations, in a highly insulting manner. What ever happened to leaving a line of retreat?
Something feels very wrong about this sentence... I get a nagging feeling that you believe he has a valid argument, but he should have been nice to people who are irrationally clinging to alternative interpretations, via such irrational ways as nitpicking on the unimportant details.
Meanwhile, a coherent hypothesis: the guy does not know QM, thinks he knows QM, proceeds to explain whatever simplistic nonsense he thinks is the understanding of QM, getting almost everything wrong. Then interprets the discrepancies in his favour, and feels incredibly intelligent.
I believe he has a valid argument for a substantially weaker claim of the sort I described earlier.
He "should have been nice to people" (without qualification) by not trying to draw (without a shred of credible evidence) a link between rationality/intelligence/g-factor and (even a justified amount of) MWI-skepticism. It's hard to imagine a worse way to immediately put your audience on the defensive. It's all there in the manual.
Why do you think so? Quantum mechanics is complicated, and questions of what is a 'better' theory are very subtle.
On the other hand, figuring out what claim your arguments actually support, is rather simple. You have an argument which: gets wrong elementary facts, gets wrong terminology, gets wrong the very claim. All the easy stuff is wrong. You still believe that it gets right some hard stuff. Why?
He should have left a line of retreat for himself.
For the reasons outlined above. Occam's razor + locality.
My argument is distinct from Yudkowsky's in that our claims are radically different. If you disagree that MWI is more probable than straw-Copenhagen, I'd like to know why.
None of the "easy stuff" is pertinent to the argument that MWI is more probable than straw-Copenhagen. For example, the interferometer calculation is neither used as evidence that MWI is local, nor that MWI is less complicated. The calculation is independent of any interpretation, after all.
if I stand a needle on it's tip on a glass plate, will needle remain standing indefinitely? No it probably won't even though by Occam's razor, zero deviation from vertical is (arguably) more probable than any other specific deviation from vertical. MWI seems to require exact linearity, and QM and QFT don't do gravity, i.e. are approximate. Linear is a first order approximation to nearly anything.
Intelligence and careful thinking --> getting easy stuff right and maybe (very rarely) getting hard stuff right.
Lack of intelligence and/or careful thinking --> getting easy stuff wrong and getting hard stuff certainly wrong.
What is straw Copenhagen anyway? Objective collapse caused by consciousness? Copenhagen is not objective collapse. It is a theory for predicting and modelling the observations. With the MWI you still need to single out one observer, because something happens in real world that does single out one observer, as anyone can readily attest, and so there's no actual difference here in any math, it's only a difference in how you look at this math.
edit: ghahahahaha, wait, you literally think it has higher probability? (i seen another of the Yudkowsky's comments where he said something about his better understanding of probability theory) Well, here's the bullet: the probability of our reality being quantum mechanics or quantum field theory, within platonic space, is 0 (basically, vanishingly small, predicated on the experiments confirming general relativity all failing), because gravity exists and works so and so but that's not part of QFT. 0 times anything is still 0. (That doesn't mean the probability of alternate realities is 0, if there can be such a thing)
From the one comment on Bohm I can find, it seems that he actually dislikes Bohm because the particles are "epiphenomena" to the pilot wave. Meaning the particles don't actually do anything except follow the pilot wave, and it's actually the the pilot wave itself that does all the computation (of minds and hence observers).
Lack of coherence? where? It's true that Bohm requires non-local HV's, but there is a non-local flavor to MWI too. The states are still non-local. Local HV's do exist. Gerard 't Hooft is working on this as we speak: http://arxiv.org/find/all/1/all:+AND+hooft+AND+gerard+t/0/1/0/all/0/1
His monologue on color, for instance.
This assumption is made by every other interpretation of quantum mechanics I know. On the other hand, I'm not a physicist; I'm clearly not up to date on things.
I meant the classical HV theories that were ruled out by actual experiments detecting violations of Bell's inequality.
Well, you didn't link to his view of qualia, but to a link where he explains why MWI is not the "winner" or "preferred" as EY claimed so confidently in his series on QM. You might disagree with him on his stance on qualia ( I do too ) but it would be a logical fallacy to state that therefore all his other opinions are also incoherent.
Mitchell Porter's view on qualia is not non-sense either, it is highly controversial and speculative, no doubt. But his motivation is sound, he think that it is the only way to avoid some sort of dualism, so in that sense his view is even more reductionist than that of Dennett etc. He is also in good company with people like David Deutsch (another famous many world fundamentlist).
As for local hidden variables, obviously there does not exist a local HV that has been ruled out ;p but you claimed there was none in existence in general.
Maybe I should have said "reading him in general..."
The rest is quibbling over definitions.