You said you suspect this is necessary, but that you hope we can recover a similar MWI, but isn't it more reasonable to expect that at the planck scale something else will explain the quantum weirdness?

When I talk about recovering MWI, I really just mean absorbing the lesson that our theory does not need to deliver determinate measurement results, and ad hoc tools for satisfying this constraint (such as collapse or hidden variables) are otiose. Of course, the foundations of our eventual theory of quantum gravity might be different enough from those of quantum theory that the interpretational options don't translate. How different the foundations will be depends on which program ends up working out, I suspect. If something like canonical quantum gravity or loop quantum gravity turns out to be the way to go, then I think a lot of the conceptual work done in interpreting NRQM and QFT will carry over. If string theory turns out to be on the right track, then maybe a more radical interpretational revision will be required. The foundations of string theory are now thought to lie in M-theory, and the nature of this theory is still pretty conceptually opaque. It's worth noting though that Bousso and Susskind have actually suggested that string theory provides a solid foundation for MWI, and that the worlds in the string theory landscape are the same thing as the worlds in MWI. See here for more on this. The paper has been on my "to read" list for a while, but I haven't gotten around to it yet. I'm skeptical but interested.

Have you given Gerard 't Hoofts idea of cellular automata which he claims salvage determinism, locality and realism any thought?

I know of 't Hooft's cellular automata stuff, but I don't know much about it. Speaking from a position of admitted ignorance, I'm skeptical. I suspect the only way to construct a genuinely deterministic local realist theory that reproduces quantum statistics is to embrace superdeterminism in some form, i.e. to place constraints on the boundary conditions of the universe that make the statistics work out by hand. This move doesn't seem like good physics practice to me. Do you know if 't Hooft's strategy relies on some similar move?

't Hooft's latest paper is the first in which he maps a full QFT to a CA, and the QFT in question is a free field theory. So I think that in this case he evades Bell's theorem, quantum complexity theorems, etc, by working in a theory where physical detectors, quantum computers, etc don't exist, because interactions don't exist. It's like how you can evade the incompleteness theorems if your arithmetic only has addition but not multiplication. Elsewhere he does appeal to superselection / cosmological initial conditions as a way to avoid cat states (macrosco... (read more)

0Quantumental8yAha, I see. So you do not share EY's view that MWI is "correct" then and the only problem it faces is recovering the Born Rule? I agree that obviously what will end up working will depend on what the foundations are :) I remember that paper by Buosso and Susskind, I even remember sending a mail to Susskind about it, while at the same time asking him about his opinion of 't Hoofts work. If I remember correctly the paper was discussed at some length over at physicsforums.com (can't remember the post) and it seemed that the consensus was that the authors have misinterpreted decoherence in some way. I don't remember the details, but the fact that the paper itself has not been mentioned or cited in any article I have read since then indicates to me that there has had to have been some serious error in it. Also Susskinds answer regarding 't Hoofts work was illuminating. To paraphrase he said he felt that 't Hooft might be correct, but due to there not being any predictions it was hard to hold a strong opinion either way on the matter. So it seems Susskind was not very sold on his own idea. Gerard 't Hooft actually does rely on what people call "superdeterminism", which I just call "full determinism", which I think is also a term 't Hooft likes more. At least that is what his papers indicate. He discuss this some in a article from 2008 in response to Simon Kochen and John Conway's Free Will Theorem. You might want to read the article: http://www.sciencenews.org/view/generic/id/35391/title/Math_Trek__Do_subatomic_particles_have_free_will%3F [http://www.sciencenews.org/view/generic/id/35391/title/Math_Trek__Do_subatomic_particles_have_free_will%3F] After that you might want to head on over to arxiv, 't Hooft has published a 3 papers the last 6 months on this issue and he seem more and more certain of it. He also adress the objections in some notes in those papers. Link: http://arxiv.org/find/quant-ph/1/au:+Hooft_G/0/1/0/all/0/1 [http://arxiv.org/find/quant-ph/1/au:+Hooft_

Stupid Questions Open Thread Round 3

by OpenThreadGuy 1 min read7th Jul 2012209 comments

8


From the last thread:

From Costanza's original thread (entire text):

"This is for anyone in the LessWrong community who has made at least some effort to read the sequences and follow along, but is still confused on some point, and is perhaps feeling a bit embarrassed. Here, newbies and not-so-newbies are free to ask very basic but still relevant questions with the understanding that the answers are probably somewhere in the sequences. Similarly, LessWrong tends to presume a rather high threshold for understanding science and technology. Relevant questions in those areas are welcome as well.  Anyone who chooses to respond should respectfully guide the questioner to a helpful resource, and questioners should be appropriately grateful. Good faith should be presumed on both sides, unless and until it is shown to be absent.  If a questioner is not sure whether a question is relevant, ask it, and also ask if it's relevant."

Meta:

  • How often should these be made? I think one every three months is the correct frequency.
  • Costanza made the original thread, but I am OpenThreadGuy. I am therefore not only entitled but required to post this in his stead. But I got his permission anyway.

Meta:

 

  • I still haven't figured out a satisfactory answer to the previous meta question, how often these should be made. It was requested that I make a new one, so I did.
  • I promise I won't quote the entire previous threads from now on. Blockquoting in articles only goes one level deep, anyway.