Cosmological Interpretations of Quantum Mechanics

It seems that there’s now a new burgeoning field bringing together multiverse studies and interpretational issues in quantum mechanics. Last year Aguirre, Tegmark and Layzer came out with with Born in an Infinite Universe: a Cosmological Interpretation of Quantum Mechanics, which claimed:

This analysis unifies the classical and quantum levels of parallel universes that have been discussed in the literature, and has implications for several issues in quantum measurement theory… the analysis suggests a “cosmological interpretation” of quantum theory in which the wave function describes the actual spatial collection of identical quantum systems, and quantum uncertainty is attributable to the observer’s inability to self-locate in this collection.

Last month there was Nomura’s Physical Theories, Eternal Inflation, and Quantum Universe where “a picture that the entire multiverse is a fluctuation in the stationary, fractal “mega-multiverse,” in which an infinite sequence of multiverse productions occurs” is invoked and:

Our framework provides a fully unified treatment of quantum measurement processes and the multiverse. We conclude that the eternally inflating multiverse and many worlds in quantum mechanics are the same.

Most recently, tonight’s arXiv listing has Bousso and Susskind’s The Multiverse Interpretation of Quantum Mechanics:

We argue that the many-worlds of quantum mechanics and the many worlds of the multiverse are the same thing, and that the multiverse is necessary to give exact operational meaning to probabilistic predictions from quantum mechanics.

I confess that I’m having trouble making sense of any of these papers. According to Bousso and Susskind, if I want to understand how quantum mechanics describes some simple, local physical system and what happens when I do measurements of it, I need to sign on to the theory of eternal inflation and the multiverse:

We will offer some principles that we believe are necessary for a consistent interpretation of quantum mechanics, and we will argue that eternal inflation is the only cosmology which satisfies those principles.

In the case of many string theory papers, one’s problems understanding their claims could often be attributed to the highly complex and sophisticated mathematical framework involved. These papers are mostly long sections of verbiage, sometimes with pictures. My inability to make sense of them must have some other source…

Update
: Lubos has an explanation of the Bousso-Susskind paper: “they’re on crack”.

Update: I suppose one could have guessed that Sean Carroll would be a fan of this. In his book he argues that the way to understand the second law of thermodynamics and the arrow of time is to invoke cosmology and the multiverse, now he seems happy to do the same thing with the interpretation of quantum mechanics. The ideas seems to be that to understand some local quantum mechanical phenomenon, you need to use cosmology and think about the horizon that is part of the deSitter geometry. I don’t find this argument any more plausible than the arrow of time one.

It does seem like this is now being promoted as the hot topic in theoretical physics, with Sean and others organizing a conference partially devoted to this at Perimeter this summer.

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64 Responses to Cosmological Interpretations of Quantum Mechanics

  1. hutom says:

    If you quote them correctly, you are lying about the universe.

  2. DT says:

    Interesting.

    In an inflationary multiverse, each universe is separated spatially (albeit over a very large distance) so this still theoretically allows one to travel from one bubble universe to another.

    Now since the many-worlds contains the ensemble of all possible scenarios, it is possible that there is a bubble universe where an advanced alien civilization exists and that has the technology to travel betwen bubble universes.

    Let’s also assume that their leader is the abducted Elvis Presley. Theoretically Possible.

    Since anything is possible as long as consistent with physics, we should anticipate this alien civilization to travel to the milkyway and start an inter-bubble war that will soon involve planet earth triggering armageddon.

    Of course, one will argue that we may belong to the universe within the ensemble which the aliens never invaded. But since infinite quantities are now allowed in physics, nevermind everyone confuse quantity with the limit theorem, without a doubt this alien civilization will have the ability to replicate itself infinitely to invade all the infinite number of universes within the ensemble.

    But since this will assign a 100% probability to the invasion scenario, this is a complete violation of the ensemble wave function. A case of inifinity over infinity.

    Wow. The things that are revealed to us by the double-slit experiment.

  3. Bertrand Gray says:

    Where do I get the feeling that the Wall Street hedge funds funding fqxi are using the same logic, reason, and math as the folks at fqxi?

  4. DT says:

    Now, with regards to unifying quantum measurement processes and the multiverse, its understanding is a simple derivation of the reformulated Schroedinger Cat.

    Imagine an astronaut who is asleep in orbit around planet Earth, which is in a verge of annihilation care-of an anti-matter death-ray using quantum mechanical effects as trigger.

    Since there is now a superposition of Earth-still-there, and Earth-blasted-into-smithereens, there is a superposition of gravity as well – a case of gravity being there and NOT there at the same time, which shouldn’t confuse the austronaut since he is asleep and unconscious. But since this is not possible (gravity and no-gravity superposition), the gravity wave function will collapse even without direct observation.

    This simple analogy with complex mathematical implications tells us that gravity, including quantum gravity is immune to quantum observational effects. Such a brilliant concept is now being applied to inflation theory.

    Only Physicists who are confused by the mathematics, like Woit, won’t figure this out.

  5. Anon says:

    The real tragedy is that these blathering idiots are occupying the resources that could be so much better spent on the many worthy young physicists who don’t have jobs.

  6. also anon says:

    >> when I do measurements of it, I need to sign on to the theory of eternal inflation and the multiverse

    as we have learned from Sean Carroll: if you scramble an egg you are a cosmologist.
    and as we have learned from Lewis Carroll: We’re all mad here.

  7. Pingback: Multiverso y mecánica cuántica « Ciencia DiY

  8. Guillaume says:

    And you could also mention the would-be modern Aristotle, crackpot David Deutsch and his multiverse-parallelized quantum computer… Seriously, I’ve just started his latest book (The Beginning of Infinity), it’s quite something. And he blames sceptical physicists for having a “bad philosophy”! Hopefully you can find some time to write a review, Peter.

  9. Francis Cornish says:

    Peter, when are you going to review Penrose’s fascinating new book, “Cycles of Time”?

  10. Tim van Beek says:

    I’d like to know if there is some consent in the String theory community about the Bousso-Susskind paper: How important is it and what should be done with it?

    A kind of review at the nearing end of a long academic career, the kind I understand and really like to read, is this:

    * Rudolf Haag: Questions in quantum physics: a personal view

  11. Christian Takacs says:

    I believe there should be a new classification of fallacy in math and physics called “Appeal to Complexity”. The way it works is, an argument or theory is proposed that is so complicated that you can’t understand it, but since you don’t want to look stupid in front of your peers, you nod your head and say solemnly “hmmm, very interesting, very sophisticated, might be possible” which will cover your ass from actually making a judgement you can be accountable for, while at the same time presenting the pretense that you actually understand the argument, thus making you look clever. The only weakness of an “Appeal to Complexity” argument is if someone not ruled by his peer’s favor (or a small child) does a sniff test and says “hmmm, It smells like bullshit”.

  12. enc says:

    @Christian Takacs: “The Emperor’s New Clothes”. The story goes exactly as you say and the hero was indeed a small child, who uttered the famous line “The Emperor has no clothes”.

  13. anon says:

    If the Lenny from 20 or 30 years ago could travel forward in time, I’m sure he’d tear the modern “multiverse” Lenny to shreds.

  14. Anon says:

    I think it deserves serious consideration whether someone like Susskind wouldn’t be a better fit for a humanities department.

  15. Peter Woit says:

    Anon,

    I think you’re being unfair to humanists. Relatively few of them are on crack.

    Francis Cornish,

    I’ve written a review for a popular publication, will write something here when it appears.

  16. Bernhard says:

    I wonder if it bothers these guys at all they´re not doing physcis anymore. “the multiverse is necessary to give exact operational meaning to probabilistic predictions from quantum mechanics.” ???? Really, what is this? I certainly don´t need to know math as good as them to smell bullshit.

    This kind of curiosity should not be put together with physics and I think anything related to these multiverses should start having their own space, their on arxiV… And leave the LHC and measurable things for “narrow minded” people who just want to make science in the old experimental fashion way… This is all going too far and I hope the new generations entering physics will understand that what these guys are doing is not bold and forward. Is just not science.

  17. Paul Wells says:

    I think the key question is if this idea makes any new predictions.

    If, for example, there was a connection between the cosmological constant and a time-varying behavior of the fine-structure constant that would be interesting. Otherwise I think it is philosophy.

  18. Peter Woit says:

    Tim van Beek,

    I suspect that Lubos’s “they’re on crack” reflects the attitude of much of the string theory community. They thank Witten (among others) for discussions about this, I’d be curious to know what he thinks.

  19. maciej says:

    Even in the Everett many world idea the “worlds” have the same physical laws and constants, e.g. the fine structure constant is the same in every “world” of Everett’s concept.

    However in the multiverse concept one imagines that the separate “worlds” may have different constants.

    Do they comment on that? (sorry for my ignorance not having read their paper).

  20. Pingback: New way of doing physics « Calcutta Chronicles

  21. Mitchell Porter says:

    Bousso and Susskind’s paper became much more comprehensible to me once I arrived at Figure 13 (page 40). I don’t agree with any of these “cosmological interpretations of quantum mechanics”, but at least I can now understand something of how B & S’s cosmology is organized. In Figure 13, you have a big causal diamond on the left, which corresponds to a stable supersymmetric vacuum state in a flat space which lasts forever. Then you have all the little causal diamonds on the right, which correspond to metastable de Sitter geometries in which supersymmetry is broken, and which decay to the supersymmetric ground state in finite time. And the idea is that there is a novel holographic duality (“FRW/CFT”, see 0908.3844) connecting spacelike slices of the eternal supersymmetric geometry with entire histories in the de Sitter patches. So the formula for this paper is “FRW/CFT eternal-inflation cosmology + the dubious philosophy that QM has no meaning unless every experiment occurs infinitely often”.

  22. Anon says:

    Shall this be called “The BS interpretation of Quantum Mechanics”? 🙂

  23. anonymous says:

    It may now be an open question of whether the authors on arxiv write better fiction than those on vixra – it used to be a no brainer to decide this. I guess crack helps in writing fiction..

  24. Crackpotl says:

    Come on, they’re obviously not on crack. That’s a ghetto drug. More likely some sort of organically grown hashish.

  25. srp says:

    I’ve become more and more unhappy with the new marriage of physics and cosmology. They used to serve as a check on one another, but now it seems like whenever people get stuck on one side they pull something bizarre out of the other to move ahead. Trouble with the Big Bang flatness problem? Invent an inflaton field! Trouble with the time reversibility of physical law and the Second Law of Thermodynamics? Appeal to the low-entropy early universe!

  26. bonk says:

    That’s true. Inflation also serves as the solution to the “monopole problem”, a non-existent problem from particle physics.

  27. Zed's dead says:

    > They thank Witten (among others) for discussions about this, I’d be curious to know what he thinks.

    Zed’s dead, baby.

    http://www.youtube.com/watch?v=eEutI_JKr7A

    3:30 – 5:15

  28. Hansi says:

    Arxiv should have some filter that papers with a certain number of words versus number of formuas ratio are automatically given to an administrator for refereeing or are automatically rejected.

    Typically, only crackpots publish dozents of pages without even one single, or only very few mathematical formulas.

    It is a typical criteria for crackpot papers not to contain interesting calculations.

    It is a shame, that people like Suesskind are publishing stuff like this.

  29. the next einstein says:

    Dear Hansi,

    The notebooks of Faraday and Bohr contained page after page of words, thoughts, and ideas, with nary an equation. Are you calling Bohr and Faraday crackpots?

  30. the next einstein says:

    p.s. I do agree that the current crop of Aguirre, Tegmark and Layzeritus papers constitute crackpottery, but it is because the ideas are completely crankish with no physical basis.

    On the other hand, Bohr and Faraday’s words reflected a true, deeper physical reality.

    Einstein had a picture of Faraday hanging in his office, next to one of Newton and Maxwell, so Einstein held Faraday in high esteem.

  31. Hansi says:

    Certainly, many of the papers of Faraday and Bohr contained only words. And, according to modern science standards, these would be certainly not be mathematical physics papers.

    Remember: the section where postet their nonsense is

    High Energy Physics – Theory

    But a theory does at least imply some degree of mathematisation.

    If they would have postet their nonsense in physics/general or some private homepage, I would not care, because I do not read physics general.

    What Suesskind is doing here is simply to spam the hep/th archive with off topic nonsense..

  32. Anon says:

    I don’t like the direction this discussion has taken. I think censoring the arxiv would be a very dangerous and unfortunate path to choose.

    I think it is good that this paper was hosted in hep-th. It just makes their embarrassment more public and humiliating in the circles where it counts, which ultimately will serve the interests of real Physics.

  33. Yatima says:

    @srp

    “Trouble with the time reversibility of physical law and the Second Law of Thermodynamics? Appeal to the low-entropy early universe!”

    Err… what?

    If you accuse someone of having to “appeal” to a low-entropy early universe you might as well accuse people of “appealing” to the heat pump if they find their fridge in a markedly off-equilibrium temperature upon opening it.

    And who has trouble with the “time reversibility of physical law” which clearly ain’t … is this 1910 or what?

  34. Bernhard says:

    Anon,

    You have a point and this applies specially for someone like Süsskind who is already famous and one can say used to be a physicist. But I wonder if we want to allow any sort of crakpotish paper in the arXiv with no moderation. Going around the internet you find so many “awesome” theories that is hard to see that physics have anything to gain with all of them populating the arXiv…

  35. chris says:

    His name is Susskind.

  36. Anon says:

    There is already moderation.

  37. Bernhard says:

    Anon,

    that there is already moderation was exactly my point. So hopefully the level of nonsense will not raise even more, otherwise it will start to be difficult to separate the usual nonsense from the sophisticated string nonsense.

  38. Cosmonut says:

    String theorists have long been trying to piggyback on eternal inflation by saying that the many bubble universes predicted by inflation correspond to string theory vacua.
    As far as I can see, the landscape of and multiverse are quite independent of each other.
    The attitude seems to be “the multiverse can’t be osberved, and neither can the string landscape, so they must be the same”.

    Now they are trying to go one step further and claim that the landscape, multiverse and many worlds of QM are one.
    I can see an attempt at “unification” going on here – just very different from the unification that was promised in the 80’s !! 😉

    Agree with Lubos that these guys are on crack. I think they mostly have been for the last decade or so.
    The quest to unify physics is increasingly turning into a farce.

  39. Peter Woit says:

    Anon, Bernhard,

    Susskind is one of the few respectable physicists I know who has had an arXiv submission rejected on grounds of sheer looniness, see

    http://www.math.columbia.edu/~woit/wordpress/?p=63

    In general though, if journals are publishing this stuff, prominent people are doing it and endorsing it, and it is the public face of the field (next month Bousso and Susskind are on a program at the World Science Festival here, funded by Templeton), the arXiv can’t reject such things. They reflect the standards of the field, can’t institute higher standards.

    Note that one place where they are doing multiverse-related censorship is that they are censoring links to this blog, a policy that seems to have had something to do with me saying mean things about a Bousso/Polchinski article in Scientific American promoting the landscape.

  40. Anon says:

    Peter, that is exactly why discretionary censorship of the arxiv is a bad thing. Those who exercise this discretion have in various known instances shown themselves incapable of controlling their baser political urges. The dictatorial behavior of the emperor of the arxiv is already bad enough. We don’t need more of that kind of thing.

  41. Bernhard says:

    Anon, Peter

    Agreed. Maybe the arXiv could create a new category for these kind of papers, because I still think hep-th does not apply. Perhaps hep-mv (for multiverse), since hep-non (for nonsense) would probably offend someone.

  42. Albert Zweistein says:

    How about hep-ut, for untestable. Or maybe hep-ps for pseudo-science? Or hep-pc for Platonic?

  43. oaf says:

    What makes anyone on this blog think hep has a monopoly on silliness?

  44. Albert Zweistein says:

    Of course hep does not, but the offerings at hep sure make the competition look stodgy.

  45. Guillaume says:

    What I find most disturbing is that arxiv seems to have become a substitute to publishing in decent peer-reviewed journals, which is not what it was supposed to be. Maybe it would be a good idea to only accept on arxiv papers that have already been submitted for publication somewhere? I’m sure a lot of garbage would immediately disappear…

  46. chris says:

    Guillaume,

    at least in my field (hep-lat) this is not true. preprints with an arXiv number older than 2 years and no journal reference are generally frowned upon and regarded as proven junk. arXiv is very effective and useful just as it is in giving the community a chance to ‘referee’ a paper before it is submitted to a journal.

  47. ark says:

    The arXiv is supposed to be ‘preprints’ so articles are posted before submission to any journal. So one cannot insist that a post has already been submitted to a journal. But it is also true that in some cases the publishers **want** people to also post on the arXiv. For example the proceedings of the Rencontres de Moriond (or will you call them crackpots?). For example for the 2010 Electroweak meeting, the instructions to contributors state in part:

    May we also suggest that you submit your contribution to the proceedings as an eprint to the arXiv.org repository.
    http://arxiv.org/
    This will ensure a long-term web persistence of your paper. Inform us of the submission number to AirXiv, by sending a mail to the secretary (specify that your proceedings are for the Moriond 2010 EW session)

    See this link
    http://indico.in2p3.fr/internalPage.py?pageId=2&confId=2065

  48. joenobody says:

    Off-topic: perhaps you’ve noticed it already, but there’s a recent paper in Nature about the measurement of the electron which appears to rule out some supersymmetric theories and, according to its authors, could conclusively rule in or out SUSY in general within the next few years, see this http://www.guardian.co.uk/science/2011/may/25/electrons-round-cosmos

  49. Paul says:

    “Our formal argument hinges on properties of what we term the quantum confusion operator…”

    There’s no way THAT could go wrong.

  50. Bernhard says:

    joenobody,

    That´s interesting. I would really like to know how much this experiment can disfavor SUSY (and how much it already did), because I find it hard to believe it can “pretty conclusively rule in or out supersymmetry”.

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