Quick Links

  • This month’s Physics Today has a long article by Wojciech Zurek, Quantum Darwinism, classical reality, and the randomness of quantum jumps. I’m not sure if there’s anything new there, but it’s a very clear exposition of what seems to me the most penetrating point of view on the measurement problem in quantum mechanics, one that gets far too little attention in the press.

    I’d like to know what this makes me in terms of various ideologies of the interpretation of QM. Am I a quantum Darwinist, or maybe a Zurekian?

  • At another extreme, getting lots of media attention while not saying anything substantive, there’s the multiverse of the Many Worlds interpretation. The media campaign to promote this is still in high gear. Recent examples include Brian Cox: ‘Multiverse’ makes sense at BBC News, this week’s New Scientist, which has a bunch of things including Multiverse me: Should I care about my other selves?, and an upcoming program here in New York that tells us that:

    We may live in a multiverse in which every possibility happens and with each new possibility the universe branches off into another of many worlds.

    The New Scientist article has Don Page pointing out that this explains the problem of evil. God likes the idea of everything possible happening all the time so much he’d rather not be bothered to stop bad things from happening:

    “God has values,” he says. “He wants us to enjoy life, but he also wants to create an elegant universe.” To God the importance of elegance comes before that of suffering, which, Page infers, is why bad things happen. “God won’t collapse the wave function to cure people of cancer, or prevent earthquakes or whatever, because that would make the universe much more inelegant.”

    For Page, that is an intellectually satisfying solution to the problem of evil. And what’s more, many worlds may even take care of free will. Page doesn’t actually believe we have free will, because he feels we live in a reality in which God determines everything, so it is impossible for humans to act independently. But in the many-worlds interpretation every possible action is actually taken. “It doesn’t mean that it’s fixed that I do one particular course of action. In the multiverse, I’m doing all of them,” says Page.

  • On the math front, I just noticed that Pieter Belmans has a blog. One of the many nice things there is his “atlas” for Spec Z[x].
  • Over at Persiflage, anyone interested in how NSF grant applications in mathematics are evaluated can find an extensive and well-informed discussion.
  • Videos from last week’s Heidelberg Laureate Forum (which features Fields Medalists and others) are available here.
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48 Responses to Quick Links

  1. Matt Leifer says:

    “I’d like to know what this makes me in terms of various ideologies of the interpretation of QM. Am I a quantum Darwinist, or maybe a Zurekian?”

    It means you are a closet Everettian in denail. Zurek is explicit that his work is a development of the Everettian program, although he does not necessarily endorse many-worlds. Still, the only way I can really make sense of Zurek’s work is within a many-worlds context. Zurek would likely disagree, but I think he is working with an unusual definition of “objective”.

  2. Peter Woit says:

    I wouldn’t really deny being an Everettian, although one suffering from not being quite sure what an Everettian is. Of the things I’ve seen purporting to describe what such a point of view is, they seem to me to range from sensible statements, clarifying a bit how to think about this, to the completely empty, heavily larded with silliness. Surely there’s a terminology to keep straight which sort of Everettian one is.

  3. Als says:

    “Over at Persiflage, anyone interested in how NSF grant applications in mathematics are evaluated can find an extensive and well-informed discussion”

    It was a depressing read. I had no idea there was so much PC-bullshit going on behind the scene.

  4. Peter Woit says:

    Funny, my reaction was the opposite. I would have thought there was MORE PC-bullshit going on behind the scenes…

  5. Alex says:

    The description of the NSF evaluation in mathematics sounds very much like how it works in astronomy, modulo some obvious differences. I’m stunned that 30% of NSF mathematics proposals get funded though! It was more like 10% in astronomy before the financial crisis, and is surely worse now.

  6. Yatima says:

    I came here to read about math and all I got was further erosion of my dwindling hope that human brains can actually generate meaningful statements.

    “It doesn’t mean that it’s fixed that I do one particular course of action. In the multiverse, I’m doing all of them”

    What the hell is this I don’t even.

    I think it was Danielewski who wrote that the writings of Heidegger prove the existence of crack back in the early twentieth century. This surely reaches that kind of level.

  7. JG says:

    “I’d like to know what this makes me in terms of various ideologies of the interpretation of QM. Am I a quantum Darwinist, or maybe a Zurekian?”

    The paywall interpretation of Quantum Mechanics

  8. Anon says:

    Alex–it is true that Astronomy gives out 10-15%, and Math about 30%, but in Astronomy they tend to give people roughly what they ask for, whereas Math cuts budget requests substantially. High Energy also is around 30% and cuts budgets substantially. One difference in High Energy is that they use external reviewers (3-4 per proposal, typically) and the panel then looks at those reviews before ranking the proposals.

  9. Don Jennings says:

    Is there a place where I can look up all the grants awarded by the NSF (or DOE) to a particular person? I think it would be rather interesting to see how much various papers have cost the public.

  10. abbyyorker says:

    darwin is behind a paywall… bummer

  11. Peter Woit says:

    For something not paywalled, there’s

    Don Jennings,
    Much information about NSF awards is searchable here

  12. CPV says:

    What the solution to the measurement problem is depends in large part on what you think the problem is, if it even exists at all. Why do you think it exists at all? Thinking that classically emergent behavior can’t occur at scales many, many orders of magnitude larger than quantum behavior seems like a strange prior. Look at turbulent flow. Look at gravity (probably).

  13. I’d love to hear about the ERC (european) version of how the NSF grant review process works.

  14. Peter Woit says:

    Goleta Beach,
    Thanks, very sorry to hear that news.

    Perl had a blog, see

  15. nick herbert says:

    One of the reasons Giordano Bruno was burned at the stake was his doctrine of multiple worlds. Bruno argued that the Church-supported doctrine of One World constituted an unjustified limit to God’s omnipotence and glory.

  16. Jeff M says:

    I don’t see how Everett solves the measurement problem. He just says that the wave function doesn’t collapse, you still have a measurement which changes things somehow. As I remember reading Everett, Schrodinger’s cat is still both alive and dead until you open the door.

  17. piscator says:

    nick: not relevant and not correct

    The ERC procedure is (partially) as follows. The proposal initially goes off to three external referees (this is the first stage). If successful in the first stage, the proposal goes to an additional four external referees and the candidate is invited to interview. Once the process closes you get to see all the referee reports. People getting to the interview stage have a 40-50% chance of getting it, the overall success rate I think is around 7 – 10%. The interview panel is large (around 16 people, most of whom are not even really close to your field). e.g PE2 which is the main panel for high-energy theory also serves not just all experimental and theoretical particle and nuclear physics, but also AMO/ tabletop atomic experiments. The interview is about 30 minutes.

  18. Don says:

    Dear Professor Woit

    I am wondering if you have looked at a possible connection between Multiverse mania today and Cantor’s set theory of ~ 100 years ago. I have been studying the status of Cantor in mathematics and it is even today contentious. There seem to be parallel sociological situations. In phyiscs, string theory and multiverse mania represent the institutional and media mainstream, and in mathematics the axiomatic method of Hilbert, and its foundations in Cantor’s set theory, seem to be the mainstream.

    The idea of transfinite numbers seems to have much in common with the idea of multiverses. But as I learn more about transfinite numbers, they seem more and more like fairy tales, or “castles in the sky”, similar to multiverse ideas. I increasingly sympathize with people that advocate finite-ist mathematics.

    Anyway, it seems there should be a connection, maybe even a lineage between the glib treatment of infinity in mathematics and the current glib treatment of infinity in the multiverse ideas.

    I apologize in advance if you have written about this in the past and I am being redundant, and would appreciate links to your thoughts about the matter.

    Thank you sincerely,

    Don DeGracia

  19. Peter Woit says:

    Sorry, but my knowledge of set theory and trans-finite numbers is minimal. So, I don’t see a lot of parallels with the multiverse, beyond the fact that both have potential problems of “glib treatment of infinity”.

  20. Chris W. says:

    Thinking—or even routinely observing—that classically emergent behavior can occur at scales many, many orders of magnitude larger than quantum behavior is not the same as understanding why it does occur, given that the world is fundamentally quantum mechanical. That is the issue that Zurek, et al, have been grappling with.

  21. Don says:

    Dear Peter

    Thank you for the reply. That’s too bad. I was hoping you might have some insights to shed on the issue. I will continue to study the issue, which seems to involve the split of math into the different camps of formalists, logicits and constructivist. Again, there seems to be a sociological dimension of comparison with current physics.

    For example, formalists accept Cantor’s ideas of “magnitudes of infinity” (e.g. transfinite “numbers”), but constructivists do not, because one cannot construct examples of such “numbers”. This seems analogous to the situation in physics, where some physicists are constructing in-principle untestable theories, vs. those who demand a strong grounding in empirical facts.

    Again, Sir, thank you for the input.

    Best wishes,


  22. BooToo says:

    As a working mathematician, I use the ideas of orders of infinity
    (countable, uncountable) and even the ordinal numbers, first uncountable ordinal, all the time; these are very well understood on a “practical” level, meaning we can
    prove everything rigorously and also have a complete understanding at an intuitive level of what is going on. This is Cantor’s beautiful universe and seems to me not at all comparable with physics, altough some try to make that stretch. For instance physicists use Quantum Mechanics to do calculations despite not understanding the measurement problem, but my impression is that there is some very basic and important level at which they (still) do not understand things. Hence all the discussion
    e.g. by Peter.

    Now though I am not in logic or set theory, I have taught “naive set theory” and can attest that everything there, including at first strange concepts like the Axiom of Choice, Russell’s Paradox and ordinal numbers, also non-well-founded sets…makes perfect sense. (And is fascinating: it is, certainly, a triumph of human thought).

    Even, say, the idea of having say different models for the real numbers, as in nonstandard analysis, seems not really objectionable. These are “models”, that is they reflect actual properties of the reals, but carry additional structure, which one may or may not want to consider at any given moment. Perhaps an analogy is that a differentiable map “carries” a lot of hidden extra structure: it defines actions on other spaces (the tangent bundle; the space of continuous functions; spaces of paths; groups of matrices; the collection of differential forms; the collection of measures; on homology and cohomology; some push forward, some pull back…) So you choose which models, and which axioms, suit your immediate purposes, and there is no contradiction. All is rigorous.

    The multiverse stuff (including the Many Worlds interpretation) seems to me to
    to be in a completely different world, not at all analogous. First of all it seems (to this outsider) to be completely non-rigorous mathematically. Evidence for this is that there are so many disagreements among experts. That doesn’t happen in math.
    More evidence is the fear leading to depression among experts that years of their lives have been lost writing preprints (8000 citations of Witten????) which may prove completely useless.
    Again, this can’t happen in math, where things are actually proven and hence intrinsically, and practically, worthwhile.

    More evidence is that, despite the potential mathematical difficulties of say string theory or quantum field theory being far beyond what many of us mathematicians encounter in our own small efforts, sometimes the techniques being attempted on these enormously difficult problems are ridiculous in their simple-mindedness (I saw a paper on the multiverse measure problem, which it is not AT ALL clear makes ANY sense at all, based on a simple Markov chain model as taught at an undergraduate level- please give me a break).

    As to constructivism etcetera, again this iscan be viewed as an issue of how much structure you want to carry along with you- for instance if you want something to be computable or verifiable and so on, but it is not really an issue of what is “right” or “wrong”. That is not the case in physics, where Nature (i.e. experiment) is the ultimate arbiter.

    So, I would answer your question more or less as follows: “Is there a useful analogy? No, not really”.

  23. Bill says:

    How come this doesn’t get more attention…

  24. Peter Woit says:

    These are not elementary particles, but quasi-particle excitations in a condensed matter system. This is interesting condensed matter physics, but has nothing to do with fundamental particle physics, or possible Majorana neutrinos, dark matter etc. If you compare the article you linked to to the Princeton press release it is derived from, you’ll see that the Princeton document does its best to hype this by bringing in neutrinos and dark matter:

    “In addition to their potential practical uses, the pursuit of Majoranas has broad implications for other areas of physics. Scientists believe, for example, that another sub-atomic particle called neutrinos, which also interact very weakly and are very hard to detect, could be a type of Majorana—a neutrino and anti-neutrino being the same particle. In addition, scientists regard Majoranas as possible candidates for dark matter, the mysterious substance that is thought to account for most matter in the universe, but which has not been directly observed because it also does not directly interact with other particles.”

    The idea that this has “broad implications” for neutrino physics or dark matter is nonsense, and you can see why the writer was taken in by this. Great physics, but not a shining moment for the communication of science to the public by my alma mater…

  25. Bill says:

    Indeed, very misleading. Does this mean that this “particle” is its own “antiparticle” only by analogy?

  26. Peter Shor says:

    @Bill: the “quasi-particle” is its own “anti-quasi-particle” in a very real sense, but these quasi-particles are not elementary particles, but are collective excitations which behave like particles, much like phonons.

  27. Don says:

    Dear BooToo

    Thank you for such a detailed reply. I do not know if Prof. Woit’s blog is an appropriate place to further develop this conversation. I have included my website in this reply. If it is possible for you to email me, perhaps, if you have time and do not mind, I can ask you some further questions about your comments. It would be most informative to speak to someone who actually uses these ideas in their work. Again, very much thanks for taking the time to explain the above. Best wishes, Don.

  28. Another mathematician says:

    Sorry, Don, but I’ll be more blunt and say that the idea of a “a possible connection between Multiverse mania today and Cantor’s set theory of ~ 100 years ago” is a complete non-starter. It’s just not worth pursuing.

  29. I am a Zurekian myself and I am not “a closet Everettian in denail” as Matt put it. I do take to heart Everett’s message: “let quantum be quantum” but the world split idea of MWI is just a very cheap shot to solving the measurement problem. Quantum evolution is only unitary and it looks like a unitary description of the collapse is a contradiction in terms, but it is not so. The solution is to use Grothendieck group construction which introduces the inverse operation to the tensor product (understood as a commutative monoid). The inverse operation reduces the dimensionality of the Hilbert space and corresponds to wavefunction collapse. To get to Grothendieck group construction one needs an additional ingredient, an equivalence relationship. QM naturally has an equivalence relationship, and Zurek discovered it: it is envariance: “what the system evolves unitarily over here can be undone by the environment evolving unitarily over there”. There is only one additional open problem: spontaneously break the Grothendieck group. In certain cases this was done rigurously, but what is lacking is a proof of the universality of the mechanism. When this is achieved it will lead to the complete solution to the measurement problem. Proving it requires advanced math.

  30. GoletaBeach says:

    12 hours until the physics Nobel.. no buzz? 51 years since the prize was given to a woman… an award to 3 all female would be great.

  31. Don says:

    Hi Another mathematician

    Thank you for the reply. Even if the thesis is wrong, it is always nice to see exactly why it is wrong. BooToo’s explanation is perfectly cogent and suggests the parallel between mutiverses and set theory is incorrect at some very basic levels. But this is a side issue with respect to the things I am wondering about math in general, for which BooToo’s reply is also helpful, but also provocative.

    I have been reading up on the old controversies from Brouwer and other critics (Weyl, Poincare) of the formalist approach (e.g. of Cantor, Hilbert, Zermelo, etc) to mathematics. Are these different philosophies of math a case of people agreeing to disagree? Do formalists have reasons for rejecting constructivists and intuitionists and vise versa? How can such seemingly incompatible approaches to math co-exist?

    These are really the issues I am trying to sort out. It is hard to ignore Poincare, for example, when he criticizes Cantor. My initial impression from what I have read is that the respective approaches could be considered “progressive” (formalists) and “conservative” (constructivists).

    If such thinking is not too far off base, the tie in with multiverse mania was an analog at this level: e.g. some one like Dr. Woit is “conservative”, insisting on traditional criteria of scientific acceptability (something I easily accept, being a bench scientist), and the multiverse people are more “progressive” in that they are willing to trash traditional scientific values, similar to how Cantor trashed the centuries long prohibition on treating infinity as a mathematical object.

    But again, my main concern is to understand, with at least as much depth as I can appreciate not being a professional in this area, the status of the situation in math.

    Again, thank you for your input.

    Best wishes,


  32. Peter Woit says:

    Don etc.
    Please, enough here about Cantor, this is just far off topic.

    Goleta Beach,
    No idea who will get the Nobel this morning. However I do predict that on Nov. 9 your neighbor Joe Polchinski will be $3 million richer….

  33. Bill says:

    They should just rename it a Nobel prize in engineering…

  34. NP says:

    Let’s not make foolish value judgments. Marconi won for the wireless, Jack Kilby won for the integrated circuit (Robert Noyce was dead), Ernst Ruska won for the electron microscope, there was a prize a few years ago for giant magnetoresistance (don’t remember the details) … all were good physics. Was it ‘engineering’ for Don Glaser to invent the bubble chamber?

  35. Here is a link to a freely available Los Alamos publication on Quantum Darwinism and randomness: http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-14-24063


  36. Hoyuna says:

    Progress in experimental HEP has slowed down considerably, so there’s a good chance that other branches of physics (especially applied physics) have struck ‘Nobel gold’. Depending on one’s level of optimism, one might predict no end for this trend.

    What do you think, Peter?

  37. tt says:

    engineering ?
    the arrogance of particle theory never ceases to dissapoint.

  38. Bill says:

    Sure, it is a great engineering invention by three engineers, so create a Nobel prize in Engineering. Don’t call it a Nobel Prize in Physics. I might be wrong though, I am not a physicist. Are LED lights used in physics besides lighting the offices and burning DVDs (although this is already outdated)?

  39. Peter Woit says:

    I personally know zero about blue leds, and don’t think arguing about what’s engineering and what’s physics is very interesting, enough of that.

    Yes, progress in HEP physics is much slower than in the past, with implications for physics Nobel prizes. More relevant though may be that if the Swedish Academy sticks to refusing to award prizes to experimental groups, that may be what will shut off HEP physics prizes. That the experimental discovery of the Higgs was not prize-worthy, and maybe never will be, shows there’s now a problem even if all of a sudden lots of great experimental discoveries are made at big colliders.

  40. GoletaBeach says:

    Blue LEDs are used throughout those particle physics experiments which use photomultiplier tubes, like, say, most of the large neutrino experiments. The emission spectrum from the Blue LEDs matches the sensitivity of most PMTs better than the old Green LEDs. The Blue LEDs are used for monitoring and calibration.

    I recall condensed matter theorists telling me in the 1970’s that Blue LEDs were impossible due to some limitation or another. Now Ultraviolet LEDs are available.
    Nakamura was unrelenting in his empirical pursuit of an idea that was quite unpopular at the time. Combine that with the practical applications and it seems like a good prize to me. Only worry is that maybe the invention of the first LED of any type might have gone unrewarded.

    It remains embarrassing that the last Nobel shared by a woman was in 1963.

    From Goleta Beach it is easier to see the College of Engineering at UCSB than the KITP. The Engineering buildings are taller, and they surround the KITP.

  41. Niclas says:

    Alfred Nobel was an inventor and engineer. I agree that he would have liked the blue LEDs. Given that 20-25 of the world’s energy is used for light then this is significant as the world needs to stop excessive energy consumption. Here is the motivation: http://www.nobelprize.org/nobel_prizes/physics/laureates/2014/advanced-physicsprize2014.pdf

  42. NP says:

    The 2014 Chemistry Prize is for ‘optical nanoscopy’. They figured out how to beat the Abbe diffraction limit. Who is to say this is ‘chemistry’ not ‘physics’? And it is the development of a useful tool, as opposed to a specific discovery of a phenomenon. Who is to say that is not ‘engineering’? It is every bit worth a Nobel Prize, be it in Chemistry not Physics.

  43. Curious Mayhem says:

    Sorry to hear about Marty Perl.

    When I first heard of the “many worlds” interpretation of quantum mechanics, I was baffled as to why it was considered science. (It isn’t, of course.) It sounded like speculative metaphysics. Anyway, later I heard about Zurek, and his work struck me as the right approach. The issue had moved from metaphysics to physics, and you can measure it in a laboratory.

    Bruno did not champion “many worlds” in the multiverse or Everett approach. He simply (and correctly) guessed that the fixed stars (in the same universe as ours) were other suns and could have planets, including planets with life. This left him with a theological problem, assuming orthodox Christian beliefs. Had he been a Buddhist, it wouldn’t have been a problem, as “many worlds, many bodhisattvas” is an acceptable, if not common, view in Buddhism. Don’t know about Islam. In Judaism, it was a view entertained by the Kabbalists, but definitely not a standard view.

  44. B'Rat says:

    nick herbert, Curious Mayhem,
    this is not what happened with Bruno.
    He was burned at stake, a barbarous act, but for his insistence in negating catholic dogmas like Trinity and so on, not because of his “many words” speculation. In fact, such idea had already been suggested more than a century before by Nicholas of Cusa, a papal legate who was made cardinal whom Bruno cited. The Aristotelian notion that there cannot be more than one World had already been condemned by the Bishop of Paris in 1277 on the basis that it limited God’s omnipotence.

    Since I do not want to start an off-topic discussion, I suggest you to add any ulterior comment on the argument in the following link, which discuss many misconceptions about Bruno’s history:

  45. Regarding einselection, which appears to be required for quantum Darwinism to be a physically viable theory, what about this? http://philsci-archive.pitt.edu/10757/


  46. anonymous says:

    Page’s thought reminds me of the classical philosophy of occasionalism, perhaps most championed by Nicolas Malebranche, who though now widely disfavored was actually quite popular in his day.

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