From Princeton to Prison

One of my graduate school classmates today sent around a link to a story about someone many of us remembered, Dragoljub Cetkovic. I somehow missed it last year when it appeared, it’s by Paul Halpern and entitled From Princeton to Prison: The ‘Boy Genius’ Who Was Recruited by John Wheeler and Sentenced by Trump’s Sister. As the story explains, Drago Cetkovic was a precocious young physicist, who John Wheeler brought to Princeton in 1974 (Barry Simon says it was actually Remo Ruffini, Wheeler’s postdoc, who had recruited him). Drago was studying quantum field theory, but wasn’t much interested in doing things like passing exams or working as a Research Assistant (the usual assignment for first-year grad students). This led to trouble and him getting kicked out of the graduate program.

By the time I arrived in Princeton, Drago was a mysterious fixture around the department, often to be found in the library. I recall a couple times asking him about what he was working on, receiving a dense and, to me, utterly incomprehensible explanation. There were rumors that he was somehow being supported on some grant or money from the IAS, but I have no idea how he made ends meet (Simon says he at times was sleeping on John Milnor’s floor). I left Princeton in 1984, and things evidently went downhill for him after that. As explained in the Halpern piece, as well as in this story from the time, in 1987 Drago for some reason left a cyanide-laced tea bag in a Princeton grocery store, and called in some sort of threat. He ended up being sentenced to five years in prison, I don’t know what happened to him after that.

Some of the stories about him refer to his supposedly threatening Barry Simon’s life (Simon was the faculty member in charge of graduate students who had to ask him to leave the program). I had heard this story, and one day when I was talking to Drago, asked him something like:

“Hey, I heard you threatened Barry Simon’s life, and that’s why he left Princeton to go to Caltech. Is that true?”

His answer:

“No, that is not true. And, if it were true, Caltech would not be far enough!”

I do wonder what happened to him, hope that he sooner or later ended up in a new and much better phase of life.

Update: My memory of those days is rather faulty, it quite likely was Nathan Myrhvold who asked him about Barry Simon. Nathan also recalls that he was working on spinor geometry. Maybe now I’d understand what he was trying to explain to me back then.

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Various News

  • Reader Chris W. pointed me to this story about what Cédric Villani, aka the Lady Gaga of French mathematics, has been up to. I see that the report of the “Mission Villani” is now available (in French or English) and it’s front page news at le Monde. There’s also an AI for Humanity website now up, and plans for all sorts of events tomorrow (video here) involving Villani and French president Macron.

    For insight into what this means, you’ll need an AI expert. I’m curious to hear if there’s anything really surprising in the report.

  • Neil Turok and collaborators have a new proposal for how to understand the Big Bang, with the headline version “The universe before the bang and the universe after the bang may be viewed as a universe/anti-universe pair, created from nothing.” There’s a short summary here, a longer paper with details here.

    The papers make various claims of predictions, I’m curious to hear from cosmologists what they think of these. Much of the papers does look like fairly straightforward QFT calculations, which I’ll try to look at more carefully when I find time.

  • The LHC is now in a machine checkout phase, ready for resurrection around Easter Sunday, with the start of beam commissioning for the 2018 run.

Update: A wealth of analyses of physics papers is available at this website and this preprint.

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What is Real?

There’s a new popular book out this week about the interpretation of quantum mechanics, Adam Becker’s What is Real?: The Unfinished Quest for the Meaning of Quantum Physics. Ever since my high school days, the topic of quantum mechanics and what it really means has been a source of deep fascination to me, and usually I’m a sucker for any book such as this one. It’s well-written and contains some stories I had never encountered before in the wealth of other things I’ve read over the years.

Unfortunately though, the author has decided to take a point of view on this topic that I think is quite problematic. To get an idea of the problem, here’s some of the promotional text for the book (yes, I know that this kind of text sometimes is exaggerated for effect):

A mishmash of solipsism and poor reasoning, [the] Copenhagen [interpretation] claims that questions about the fundamental nature of reality are meaningless. Albert Einstein and others were skeptical of Copenhagen when it was first developed. But buoyed by political expediency, personal attacks, and the research priorities of the military industrial complex, the Copenhagen interpretation has enjoyed undue acceptance for nearly a century.

The text then goes to describe Bohm, Everett and Bell as the “quantum rebels” trying to fight the good cause against Copenhagen.

Part of the problem with this good vs. evil story is that, as the book itself explains, it’s not at all clear what the “Copenhagen interpretation” actually is, other than a generic name for the point of view the generation of theorists such as Bohr, Heisenberg, Pauli, Wigner and von Neumann developed as they struggled to reconcile quantum and classical mechanics. They weren’t solipsists with poor reasoning skills, but trying to come to terms with the extremely non-trivial and difficult problem of how the classical physics formalism we use to describe observations emerges out of the more fundamental quantum mechanical formalism. They found a workable set of rules to describe what the theory implied for results of measurements (collapse of the state vector with probabilities given by the Born rule), and these rules are in every textbook. That there is a “measurement problem” is something that most everyone was aware of, with Schrodinger’s cat example making it clear. Typically, for the good reason that it’s complicated and they have other topics they need to cover, textbooks don’t go into this in any depth (other than often telling about the cat).

As usual these days, the alternative to Copenhagen being proposed is a simplistic version of Everett’s “Many Worlds”: the answer to the measurement problem is that the multiverse did it. The idea that one would also like the measurement apparatus to be described by quantum mechanics is taken to be a radical and daring insight. The Copenhagen papering over of the measurement problem by “collapse occurs, but we don’t know how” is replaced by “the wavefunction of the universe splits, but we don’t know how”. Becker pretty much ignores the problems with this “explanation”, other than mentioning that one needs to explain the resulting probability measure.

String theory, inflation and the cosmological multiverse are then brought in as supporting Many Worlds (e.g. that probability measure problem is just like the measure problem of multiverse cosmology). There’s the usual straw man argument that those unhappy with the multiverse explanation are just ignorant Popperazzi, unaware of the subtleties of the falsifiability criterion:

Ultimately, arguments against a multiverse purportedly based on falsifiability are really arguments based on ignorance and taste: some physicists are unaware of the history and philosophy of their own field and find multiverse theories unpalatable. But that does not mean that multiverse theories are unscientific.

For a much better version of the same story and much more serious popular treatment of the measurement problem, I recommend a relatively short book that is now over 20 years old, David Lindley’s Where does the Weirdness Go?. Lindley’s explanation of Copenhagen vs. Many Worlds is short and to the point:

The problem with Copenhagen is that it leaves measurement unexplained; how does a measurement select one outcome from many? Everett’s proposal keeps all outcomes alive, but this simply substitutes one problem for another: how does a measurement split apart parallel outcomes that were previously in intimate contact? In neither case is the physical mechanism of measurement accounted for; both employ sleight of hand at the crucial moment.

Lindley ends with a discussion of the importance of the notion of decoherence (pioneered by Dieter Zeh) for understanding how classical behavior emerges from quantum mechanics. For a more recent serious take on the issues involved, I’d recommend reading something by Wojciech Zurek, for instance this article, a version of which was published in Physics Today. Trying to figure out what “interpretation” Zurek subscribes to, I notice that he refers to an “existential interpretation” in some of his papers. I don’t really know what that means. Unlike most discussions of “interpretations”, Zurek seems to be getting at the real physical issues involved, so I think I’ll adopt his (whatever it means) as my chosen “interpretation”.

Update: For another take on much the same subject, out in the UK now is Philip Ball’s Beyond Weird. The US version will be out in the fall, and I think I’ll wait until then to take a look. In the meantime, Natalie Wolchover has a review at Nature.

Update: There’s a new review of What is Real? at Nature.

Update: Jim Holt points out that David Albert has a review of the Becker book in the latest New York Review of Books. I just read a print copy last night, presumably it should appear online soon here [Review now available here].

Update: Some comments from Adam Becker, the author of the book.

I won’t try to rebut everything Peter has said about my book—there are some things we simply disagree about—but I would like to clear up two statements he makes about the book that are possibly misleading:

Peter says that I claim the answer to the measurement problem is that “the multiverse did it.” But I don’t advocate for the many-worlds interpretation in my book. I merely lay it out as one of the reasonable available options for interpreting quantum mechanics (and I discuss some of its flaws as well). I do spend a fair bit of time talking about it, but that’s largely because my book takes a historical approach to the subject, and many-worlds has played a particularly important role in the history of quantum foundations. But there are other interpretations that have played similarly important roles, such as pilot-wave theory, and I spend a lot of time talking about those interpretations too. I am not a partisan of any particular interpretation of quantum mechanics.

Second, I don’t think it’s quite fair to say that I paint Bohr as a villain. I mention several times in my book that Bohr was rather unclear in his writing, and that sussing out his true views is dicey. But what matters more that Bohr’s actual views is what later generations of physicists generally took his views to be, and the way Bohr’s work was uncritically invoked as a response to reasonable questions about the foundations of quantum mechanics. It’s true that this subtlety is lost in the jacket flap copy, but that’s publishing for you.

Also, for what it’s worth, I do like talking about reality as it relates to quantum mechanics. But I suppose that’s hardly surprising, given that I just wrote a book on quantum foundations titled “What Is Real?”. I’d be happy to discuss all of this further over email if anyone is interested (though I’m pretty busy at the moment and it might take me some time to respond).

Posted in Book Reviews, Quantum Mechanics | 74 Comments

This Week’s Hype

Many thanks to Sabine Hossenfelder for her efforts to debunk the attempt to use Hawking’s death as a platform for multiverse hype. See her posting at Backreaction for a good explanation of what is going on here.

To summarize the problem, there are loads of news stories out there telling the public that Stephen Hawking’s ‘breathtaking’ final multiverse theory completed two weeks before he died, Stephen Hawking’s Final Paper Proposes Way to Detect the ‘Multiverse’, etc., etc. Cosmologist Carlos Frenk and theorist Thomas Hertog seem to be among those encouraging this nonsense.

This is all based on this recent paper by Hawking and Hertog, which contains nothing like a way to “detect the ‘Multiverse'”. It’s a toy model of bubble universe formation, one the authors admit they can’t even solve:

However, the setup we have considered does not allow us to describe the transition from the quantum realm of eternal inflation to a universe in the semiclassical gravity domain. This is because our duals are defined in the UV and live at future infinity. It therefore remains an open question whether the conjectured smoothness of global constant density surfaces impacts the eternity of eternal inflation. To answer this will require a significant extension of holographic cosmology to more realistic cosmologies

Their calculations inspire them to state: “… we conjecture that eternal inflation produces universes that are relatively regular on the largest scales”, but this is just an extremely vague conjecture without much backing it. Using it to get press stories published claiming to have found a way to “detect the ‘Multiverse'” is just absurd, and it’s sad to see Hawking’s passing memorialized with a cloud of ridiculous hype.

Update: Another detailed explanation of what is going on here, from Ethan Siegel. His summary:

There are no observable consequences; there is nothing to measure; there is nothing to test. There’s no prediction about the end of the Universe, and there are no robust conclusions we can draw about its beginning. There are tremendous limitations to the implications of this work, and there are few compelling reasons to believe that their toy model has relevance for our physical Universe. It is a seed of an idea that itself is controversial, based off of an also-controversial foundation, and this is a very small step in its development. Furthermore, all of what they do is based on the Hartle-Hawking no-boundary conjecture, which is still not generally accepted as true. The authors go so far as to admit, in the discussion of this paper, that even within their toy model, they have not shown that there is a non-Multiverse-inducing exit to eternal inflation:

“It therefore remains an open question whether the conjectured smoothness of global constant density surfaces impacts the eternity of eternal inflation.”

Posted in This Week's Hype | 7 Comments

Abel Prize to Langlands

The 2018 Abel Prize has been awarded to Robert Langlands, an excellent choice. The so-called “Langlands program” has been a huge influence on modern mathematics, providing deep insight into the structure of number theory while linking together disparate fields of mathematics, as well as quantum field theories and physics.

The Abel Prize site provides a wealth of information about Langlands and his work. Davide Castelvecchi at Nature appropriately describes the Langlands program as a “grand unified theory of mathematics” (Edward Frenkel’s Love and Math popularized this description).

Many blog posts here have discussed the Langlands program and ideas that have developed out of it. For a good example of how wide the impact of these ideas has been, this week the Perimeter Institute will be hosting a conference discussing the latest work on the geometric version of the Langlands program, as well as connections to gauge theory and conformal field theory.

For the original work of Langlands himself, besides the material at the Abel site, the AMS Bulletin has recently published a long article by Julia Mueller. For the original sources and a wealth of other material written by Langlands himself, see the IAS site that collects his writings.

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Stephen Hawking 1942-2018

Front-page on every news source today is the sad report that Stephen Hawking died yesterday at the age of 76. For the best description of his scientific accomplishments, I recommend the obituary in the Guardian written by his sometime collaborator Roger Penrose.

I was going to write a little bit about one time I heard Hawking speak (or rather, his student interpret for us his speech), which was at the IAS back in the early 1980s. I just noticed though that evidently John Baez was at the same talk (he was an undergrad, I was a grad student), and describes it well here.

At the time I remember that many thought that quantum gravity would be understood within a few years, and that Hawking would not be able to live longer than another year or two, given the nature of the disease he was suffering from. It’s wonderful that the second of these turned out to be so wrong.

While Hawking was already a star in the physics community back then, his celebrity with the wider public came later. Of all the scientists who over the years have achieved some degree of celebrity, I can’t think of another one who so much both deserved and enjoyed the public attention.

Update: There are dozens of articles appearing discussing Hawking’s life and work. One you may not have seen which I enjoyed is from Nathan Myhrvold.

Update: Another piece by someone who worked with Hawking, Marika Taylor. It includes some discussion of his views on M-theory.

Update: Hawking has inspired some new theorizing from Niall Ferguson.

Posted in Obituaries | 13 Comments

Recent Developments in Constructive Field Theory

This week there’s a mini-workshop here at Columbia organized by the probabilists, on Recent Developments in Constructive Field Theory. I’ll be attending some of the talks, will write more here if I can come up with something constructive to say.

Update: One of the talks today was Sourav Chatterjee on Yang-Mills for Probabilists, explaining what Yang-Mills and lattice gauge theory are, along the lines of this preprint. The discussion brought back memories of my grad school days and early research, but I fear didn’t give much cause for optimism that there will be much progress anytime soon on a rigorous understanding of 4d Yang-Mills theory.

Update: Today Scott Sheffield gave a talk on Gauge theory and the three barriers. He started with the initial motivation of finding a continuum theory of random surfaces giving an alternative representation of gauge theory in 4d (this goes back to Polyakov and others around 1980). There’s not much progress on this, but the question has inspired a wealth of results involving in some sense random surfaces. For some details of all of this, one place to look is the website of Sheffield’s recent graduate course.

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Presumptuous Blogging

John Horgan at Scientific American today has an interview with Martin Rees in which Rees says:

It’s presumptuous (as some people like Woit and Smolin have done) to deride the way some manifestly brilliant people choose to dedicate their scientific lives.

I generally try and be careful to criticize not people, but the arguments they are making. Rees and others (including a Cambridge University Press referee for Not Even Wrong, who basically thought I had good points, but was presumptuous to be making them) often seem offended that I or Lee Smolin are challenging arguments from those smarter than ourselves. It’s true that there is a problem with this: bad arguments of the kind I’m criticizing should be challenged by the leading figures in the field, not by me. In particular, many particle theorists smarter and more distinguished than myself are well aware of the problem of multiverse mania, but doing nothing about it, as it destroys the credibility of their field. Among the few personal criticisms of some leading theorists that I have is that they’re not doing the job they’re paid for here, and I’m not happy wasting my time trying to (presumptuously) do it for them.

On the presumptuous behavior front, here’s some more of it:

  • Rees’s arguments are the usual multiverse propaganda, including the usual red-herring argument defending the multiverse as science:

    It’s sometimes claimed that domains that are in principle unobservable aren’t part of science. But not even the most conservative astronomer would take this line. We’re in an accelerating universe where distant galaxies will disappear over a horizon, and their far future would never be in principle observable. So it’s natural to suppose that there are galaxies that are already beyond the horizon and so forever unobservable. If you’re in the middle of the ocean, you’d be surprised if its boundary lay just beyond your horizon. Likewise, astronomers are confident that the volume of space-time within range of our telescopes — what astronomers have traditionally called ‘the universe’ – is only a tiny fraction of the aftermath of our big bang. We’d expect far more galaxies located unobservably beyond the horizon.

    As usual, Rees gives no evidence for his claim that those skeptical that the multiverse is science are just ignoramuses who don’t understand the notion of indirect evidence for a scientific theory.

    Multiverse mania goes on and on, for instance here and here.

  • Among the more presumptuous things I’ve done, there’s last week’s talk.
  • I recently noticed here the analysis that:

    I “predict” that if by about 2020 the LHC or cosmology do not show any concrete evidence of supersymmetry or superstrings, physicists will attack string theory the way the Huns attacked Rome. Like the Huns, Lee Smolin, Peter Woit, and Roger Penrose have already started encircling string theory, abiding their time, and waiting for the strike. They seem to have read The Rise and Fall of the Roman Empire carefully.

    I’ve never read Gibbon. If one accepts the analogy though, I think it’s conventional wisdom that the String Wars were back in 2006, we didn’t wait for 2020. All the evidence I’ve seen recently is that most string theorists have now given up on the idea that evidence for supersymmetry or string theory will appear at the LHC. Those attempting to defend Rome now are trying to backpedal on their claims from a decade ago. They now argue that finding nothing at the LHC isn’t surprising and doesn’t matter, but this rear-guard action likely will not be effective.

  • More evidence that hopes for LHC-scale SUSY are now pretty much dead can be found by looking at the slides from the recent Aachen workshop on Naturalness, Hierarchy and Fine-Tuning. The debate among theorists has now moved on to trying to figure out what conclusion to draw from the failure of widely-promoted claims about “fine-tuning”. One motivation for such claims was that in string theory-based models the CC and Higgs potential are supposedly calculable, with expected results from dimensional analysis that are exponentially large (Planck scale) compared to observations. On this front, an obvious conclusion to draw is just that these models (which are complicated and predict nothing else anyway) are wrong.
  • I suppose it really is presumptuous to make a snarky comment about a talk by someone clearly more hard-working and smarter than I am. In any case, I just noticed that slides for Nima Arkani-Hamed’s talk Three Cheers for Shut Up and Calculate! are now available here. I had written about this here without knowing what the talk had been about, based on the historical origin of the “Shut Up and Calculate!” slogan (and thus assuming the measurement problem would be a main topic). From the slides, Arkani-Hamed’s talk wasn’t at all about the measurement problem, but largely about quantum gravity, with many slides of speculative claims about new emergent versions of space-time and quantum mechanics (backed by one slide about calculating amplitudes as volumes). I’m quite sympathetic to what he has to say about the importance of prioritizing well-defined calculations over meaningless verbiage, but it seemed to me that in this talk he wasn’t really taking his own advice. I can’t help wondering who it is that Arkani-Hamed thinks should “Shut up” about vague ideas about quantum gravity and stick to well-defined calculations.

Update: For more presumption, see the latest at Backreaction.

Update: Lee Smolin has been edited out of the list of the presumptuous in the Rees interview, but I’m rather proud to be presumptuous, so I’m still there, and a link has been added to this blog posting.

Posted in Multiverse Mania | 28 Comments

Rochester Colloquium Talk

I’m heading up to Rochester this evening, will give a colloquium talk there in the physics department on Wednesday at 3:45. I’ll put up a link to the slides after the talk, for now, here’s the abstract:

Particle theory: a view from a neighboring field

High energy particle physics faces a challenging future, largely because of the overwhelming success of the Standard Model. The LHC discovery of a Higgs particle with exactly the predicted properties, coupled with the lack of evidence there for “Beyond the Standard Model” physics, has led some to characterize this as a “crisis”.

In this talk I’ll consider the current situation from a somewhat unusual point of view, that of someone who began his career in physics departments doing particle theory, but then moved to mathematics departments. The field of mathematics has complex and close ties to fundamental physical theory, and the cross-cultural perspective it provides may be of interest.

: Apologies for the earlier mistake (I had “Thursday” instead of “Wednesday” above). The slides for the talk are available here.

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Applied Group Theory

I just noticed that Greg Moore has been teaching a wonderful course in recent years with the misleadingly bland title of Applied Group Theory. His choice of the topics he wants to cover given here is an excellent one and a good outline for anyone trying to get themselves a serious education in the modern overlap of math and physics.

The problem with this outline is that it’s far too ambitious to cover in a one-semester course, starting just from basics. Moore notes that in 2008 and 2009 versions of the course he only got through roughly half the topics, with students still complaining about the fast pace of the course. In 2013 he only made it through two out 21 topics, but in doing so generated two book-length documents of notes:

These each contain a wealth of valuable material. I do hope he someday writes up the other 19 topics, but if he does it the way he has been going, the length might turn out to be around 4000 pages, so that might take a while. In the meantime, an account of some of them is available here.

In addition, there’s also a list of suggested topics for term papers, nearly a hundred of them, each with a description of an interesting issue that has been a topic of significant research, with references for where to start learning about the topic.

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