Terrifying Odyssey Through a Cursed World

Posted on November 18, 2019 by woit

The great German artist Anselm Kiefer now has a show up in London at the White Cube Bermondsey gallery, with a review in the Guardian entitled Terrifying Odyssey Through a Cursed World. The review describes some of the works as follows:

Another room is given over to panoramic blasts of brown and black that map sweeping vistas of desolate fields. A road twines through a morass of mud and collaged sticks. Lines of fence poles vanish in the distance. These scenes are drawn in black on a vertiginous scale. Kiefer uses perspective, the Renaissance technique of showing the real world shrinking towards a single vanishing point, to define his landscapes – but the perspective view is a transparency on top of a muddy tumult of colour and texture, with real, 3D stuff stuck over that in turn. From the right distance, the picture of a landscape can be read clearly, like a painting by Van Gogh. Go closer and the picture dissolves in a mess of bulges and muck.

What’s the inspiration for these works (besides the Holocaust)?

These landscapes are entitled Superstrings, a reference to string theory, an influential idea in contemporary physics that seeks to unify quantum mechanics with Einstein’s relativity.

and the show is entitled Superstrings, Runes, The Norns, Gordian Knot. The gallery website explains:

White Cube is pleased to present an exhibition of new work by Anselm Kiefer. The exhibition brings together many of the interests that have characterised Kiefer’s work for decades, including mythology, astronomy and history. Located across the entire Bermondsey space, it features a large-scale installation and paintings that draw on the scientific concept known as string theory.

The Guardian review continues:

The main gallery at White Cube Bermondsey is already pretty bleak in its featureless emptiness. Kiefer makes it work for him by heightening the chill, turning the White Cube into a morgue for Europe. Snow-covered landscapes with none of the cheer of Bruegel stretch away to infinity. They are marked with sticks as black as gravestones and nets that catch at nothing. Kiefer’s science reading clearly hasn’t cheered him up. The curvy grids of space-time become horrible wire traps in a devastated nowhere. We might be on the no-man’s land of the Ukraine border. Anyway, this place has got death in its hard black furrows.

Another review, at City A.M. tells us more about Kiefer’s motivations:

This is where we come to string theory – the monolith of Kiefer’s new show. Though he admits that he doesn’t quite understand what string theory is, Kiefer professes complete fascination with the idea that there is a scientific equivalent to the allegorical Gordian Knot – an idea that he picked up after thirty years of subscribing to Spektrum, a German monthly science magazine…

String theory cannot be verified empirically. Rather, it is an attempt to provide an all-encompassing description of the universe. And that, says Kiefer, is just why it is beautiful. “I suppose it’s like painting,” he says. “You cannot prove if a painting is good or bad. That is the point of it – it is descriptive… and there’s something sublime in that.”

From the images available, the work does look quite amazing. Kiefer quite possibly has gotten to the very heart of superstring theory, seeing in it a dark, desolate and blasted mythology which “cannot be verified empirically.”

Posted in Uncategorized | 4 Comments

The Man Who Solved the Market

Posted on November 14, 2019 by woit

There’s an excellent new book out about Jim Simons and Renaissance Technologies, The Man Who Solved the Market, by Gregory Zuckerman. I recommend it enthusiastically to anyone interested in the story of how a geometer ended up being worth \$23 billion. Lots of other mathematicians and physicists have also been involved in this over the years.

I first heard about Simons and his investment operation when I was a postdoc at Stony Brook in the mid-eighties, and have heard bits and pieces of this story from various sources over the years, sometimes clearly distorted in the retelling. It’s very satisfying to finally get a reliable explanation of what Simons and those working with him have been up to all this time. For those with more interest than me in the details of quant strategies, the book provides far and away the most information available about how Simons and RenTech have been making so much money so successfully. The author managed to get some degree of cooperation from Simons, and was thus able to get a lot of those involved with him to talk. As a result, while this isn’t an “authorized” biography, it’s written from a point of view rather sympathetic to Simons.

One question that keeps coming up in the book is that of motivation. Why did Simons abandon a highly successful career doing research mathematics in order to focus on making as much money as possible? Part of the answer is that, from the beginning, Simons always had one foot out of the research math world, playing poker and trading commodities even when he was a graduate student working with Chern at Berkeley. Later, while employed at the IDA in Princeton, he spent time working not just on government projects but on the mathematical analysis of stock market trading strategies. While I’ve often heard the story of how he was fired from IDA after publicly criticizing the Vietnam War, less well known is that a big problem was that he was quoted in Newsweek saying he planned to work on his own projects, not government ones, until the war was over.

Unfortunately, the book has very little to say about a question I’m fascinated by: what does Simons intend to do with the \$23 billion (and counting, the RenTech Medallion Fund that he has a large piece of continues to be an incredible money-making machine)? There’s very little in the book about his philanthropic activities, the most visible of which are at the Simons Foundation, which now has assets of nearly \$3 billion with amounts of the order of \$300 million/year coming in as income and going out as research funding. I think that on the whole Simons had made excellent choices with the math and physics that he has decided to fund, from the Simons Center for Geometry and Physics at Stony Brook to a wide array of programs funded by his foundation.

A question that keeps reappearing throughout the book is that of the social significance of RenTech. It’s a rather pure test case for the moral question about quant investing: would the world be better off without it? In the case of the main money-maker, their Medallion fund, it’s hard to argue that the short-term investment strategies they use provide important market liquidity. The fund is closed to outside investors, and makes money purely personally for those involved with RenTech, not for institutions like pension funds. So, the social impact of RenTech will come down to that of what Simons and a small number of other mathematicians, physicists and computer scientists decide to do with the trading profits (calculated by Zuckerman at over \$100 billion so far).

Simons himself has engaged in some impressive philanthropy, but one perhaps should weigh that against the effects of the money spent by Robert Mercer, the co-CEO he left the company to (Zuckerman discusses Mercer in detail). Mercer and his daughter have a lot of responsibility for some of the most destructive recent attacks on US democracy (e.g. Breitbart and the Cambridge Analytica 2016 election story). In the historical evaluation of whether the world would have been better off with or without RenTech, the fact that RenTech money may have been a determining factor in bringing Trump and those around him to power is going to weigh heavily on one side.

Posted in Book Reviews | 14 Comments

Various Links

Posted on November 12, 2019 by woit

Now back from a trip to the West Coast, here are some accumulated things that may be of interest:

  • One thing I didn’t do while there was attend the 2020 Breakthrough Prize symposium. For videos of three talks about supergravity, see here. At the time of the award I wrote here about why a \$3 million prize for a failed idea about particle theory was a bad idea. Listening to the talks, I think an even worse idea is telling the public that this is a great example of why they should trust science.
  • For another dubious idea from the West Coast, in January the KITP is bringing high school teachers to Santa Barbara to teach them about Spacetime, Holography, and Entanglement. Most of the programs the KITP has run for teachers (see here) have been devoted to explaining important, solid science. Back in 2001 when they promoted string theory I thought that was a bad idea, this latest one isn’t much better. Again, when the credibility of science is under attack, why go to the public (or, in this case high school teachers) to promote a highly speculative research program? Is it really a good idea for high school teachers to be exposed to this kind of hype, presumably with the hope that they’ll somehow transmit it to their students?
  • On the evergreen topic of bad multiverse science, Scott Alexander here defends multiverse speculation, responding to Jim Baggott’s article. He and the authors of the more than four hundred comments debate at length a red-herring issue. Alexander writes:

    My understanding of the multiverse debate is that it works the same way [as respectable paleontology]. Scientists observe the behavior of particles, and find that a multiverse explains that behavior more simply and elegantly than not-a-multiverse.

    Yes, if theorists had a simple, elegant multiverse theory with lots of explanatory power, you could get into interesting arguments about its testability and whether the idea was solid science or not. The problem is that no such multiverse theory exists. If you want to talk about the MWI multiverse, your problem is that solving the measurement theory problem by just saying “the multiverse did it” may be “simple” and “elegant”, but it’s also completely empty. If instead you want to talk about the cosmological multiverse, the problem is that you don’t have a theory at all (and the actual fragments of a theory you do have are complicated and ugly). For more about this, see my posting and article on Theorists Without a Theory.

For something more positive, while traveling I noticed two quite interesting articles which explain in a detailed technical way approaches to two of the great unsolved problems of our time, while carefully discussing why the approaches have not (yet?) worked, leaving the great problems unsolved.

  • For mathematics and the Riemann Hypothesis, see Alain Connes and Caterina Consani’s article The Scaling Hamiltonian, about the attempt to understand the zeros of the Riemann zeta function in terms of the properties of a specific Hamiltonian operator, which in some sense is a generator of a group of scaling transformations.
  • For physics and quantum gravity, see Donoghue’s A Critique of the Asymptotic Safety Program, which has a detailed discussion of the problems with making sense of both quadratic gravity Lagrangians and the idea of a non-trivial fixed point gravity theory theory. I was interested to see that he has a lot to say about the Lorentzian vs. Euclidean signature issue, something often ignored.

Finally, I recommend reading Elizabeth Landau’s interview at Quanta with astronomer Virginia Trimble and Trimble’s excellent advice to us all:

Pay attention. Someday, you’ll be the last one who remembers.

Update: Two more math-related items well worth a look:

Update: Yet another blog entry from Scott Alexander about the multiverse, with more hundreds of comments. What is it with the fascination for this empty argument?

At BBC Science Focus, more multiverse promotion from Sean Carroll. He does end though by getting to the real point (note that when theoretical physicists say a question is “hard to answer”, it means they have no idea how to answer it):

Many-Worlds is a lean and mean theory, but it’s possibly too lean and mean; there is very little structure to rely on, so questions like “Why do probabilities behave the way they do?” and “Why is classical mechanics such a good approximation to the world we see?” are hard to answer.

This is exactly the problem that those arguing over this at Slate Star Codex and elsewhere don’t seem to understand: saying “all is the Schrodinger equation” doesn’t tell you how to connect the theory to the world we observe. Adding in an ontology of multiple universes does nothing at all to solve this problem.

Posted in Uncategorized | 21 Comments

Today’s Hype

Posted on October 29, 2019 by woit

Hype about string theory and fundamental physics seemed to have been dying down recently, with only three editions here so far in 2019 of This Week’s Hype. Today however brings a bumper crop of the highest quality, with new examples from a few of the world’s most prominent theoretical physicists. Today’s hype neatly exemplifies the two main current genres of hype about string theory and supposed new fundamental physics. The first is the old-school genre of string theory hype we’ve now been seeing for 35 years: “string theory makes a testable prediction” (no, it doesn’t). The second is the new, post-modern variety: no actual theory, just a grandiose claim that space and time have been replaced, although it’s unclear by what.

Trend: Cosmic Predictions from the String Swampland

In the subtitle of this APS Physics piece from Cumrun Vafa, we learn that the string swampland has “led to testable predictions about dark energy.” If you read the article trying to find the testable predictions of string theory, you’ll get to Figure 3, where the caption says “The colored curves are string theory predictions for dark energy for different values of c.”

The problems with this include:

  • This is based not on a theory or calculation, but on a conjecture (see e.g. here) that consistent string vacua have certain properties.
  • Many experts disagree with this conjecture. In particular it would imply that the well-known supposed metastable string vacua of KKLT are inconsistent, and that is a matter of controversy.
  • This conjecture is not the sort of thing that can be proved one way or another, since it is not about something well-defined. The non-perturbative formulation of string/M-theory necessary to get a well-defined answer to such questions about string vacua remains unknown. You can make various conjectures about the behavior of this unknown theory, but then your swampland conjecture is a conjecture about a conjecture.
  • The conjecture involves an unknown constant “c”. Unless you know what “c” is, you don’t actually have a prediction.

In his conclusion, Vafa writes:

In the next 5–10 years, we may know, for example, whether dark energy is constant or not. If it is, that could pose a serious blow to string theory. But if dark energy is found to be changing, could that observation be the first experimental evidence for ideas emanating from string theory?

The most likely possibility over the next 5-10 years is that measurements continue to be compatible with constant dark energy. I don’t believe for a minute that 10 years from now after that result is in you will see Vafa or anyone else giving up on string theory or even admitting it has suffered a “serious blow”. On the other hand, if there is any evidence for a varying dark energy, Vafa or others will surely claim it as “evidence for string theory”, which it will not actually be.

Over the last 15 years I’ve often written here about this “Swampland philosophy”, which never made much sense to me. I didn’t understand back in 2005 and still don’t understand now why conjectures that behavior you don’t observe in the real world might be inconsistent with some other conjectures about an unknown M-theory are supposed to be of interest. The sociological motivation here is rather clear though: the KKLT-based “anthropic landscape” philosophy has not worked out well for the field, and the hope is to disentangle the subject from that morass. A good explanation of what is going on is provided by this (stolen from Will Kinney, who also has a lot to say about the whole swampland business):

Cosmic Triangles Open a Window to the Origin of Time

This is a different sort of hype, with no direct relation to string theory. In this genre of hype, you don’t have any connection between your calculation and either experiment or a fundamental theory, but this doesn’t stop you from making grandiose claims. What’s behind this particular article is this paper, which develops a nice calculational method exploiting conformal symmetry. What’s not made clear in the Quanta article is that this has no connection to anything measurable. As the authors of the article explain:

In this paper, we have worked under the lamppost of weakly broken conformal symmetry. This has allowed us to derive particularly clean insights into the analytic structure of inflationary correlators. However, it also restricts the strength of the couplings between the inflaton and additional massive fields. This makes the observational challenge to detect these effects enormous.

In other words, this is about speculative models in which the observable effects described at length in the Quanta article would be unmeasurably small.

The post-modern hype come into play with the argument that these conformal-symmetry based calculations somehow tell us how to replace space and time.

This suggests that the temporal version of the cosmological origin story may be an illusion. Time can be seen as an “emergent” dimension, a kind of hologram springing from the universe’s spatial correlations, which themselves seem to come from basic symmetries. In short, the approach has the potential to help explain why time began, and why it might end. As Arkani-Hamed put it, “The thing that we’re bootstrapping is time itself.”

If you’re trying to understand the origin of this particular dollop of hype, it’s a good idea to keep in mind something Arkani-Hamed said at a talk about Lance Dixon’s work back in 2013:

… I AM an ideologue. In my defense at least I can say that I’m a serial ideologue, in the sense that I’ll take totally different ideologies and drop the last one without thinking about it, but it’s very important for me personally to be an ideologue when I’m working on something…
So, usually I’ll get up when I talk about scattering amplitudes and give a long introduction about how spacetime is doomed, we have to find some way of thinking about quantum field theory without local evolution in space time and maybe even without a Hilbert space and blah-blah-blah. This is all very high-falutin stuff, this is stuff that Lance wouldn’t be get caught dead saying. I think none of these guys would ever say something that sounds so pretentious, but I have to say it, you know I have to say it, because this is the only way I can get up in the morning, and like “I suck again, OK, here we go, I’m doing it because spacetime is doomed, I swear to God, right”.

I’m actually rather sympathetic to the “bootstrap” philosophy in some general sense, which I’d interpret as “all is unitary representation theory of the conformal group”, i.e. that constraints of conformal symmetry, analyticity and unitarity are almost enough to determine a fundamental theory. The 1960s version of this, trying to get strong interaction physics purely from such general principles, didn’t work out, but I’ve become more and more convinced that representation theory and fundamental quantum field theory are very deeply intertwined. I do think though that to get anywhere you’re going to need to either work top-down (i.e have an actual fundamental theory and derive its implications) or bottom up (i.e. use observations to find the route to better theory).

Will head out soon for a short vacation in Northern California (if it hasn’t burned to the ground). I had thought about stopping by the 2020 Breakthrough Prize Symposium, but decided listening to talks about why supersymmetry/supergravity got a $3 million award would not be good for my blood pressure.

Update: Those interested in KKLT vs. Swampland debates might be interested in the latest from Tom Banks. He makes a detailed case against KKLT/eternal inflation/Landscape models, which string theory Swampland enthusiasts may find appealing. They should however note what he has to say about string theory itself:

A more sensible attitude, which I share, is to accept that string theory defines some models of quantum gravity, but obviously not the one that corresponds to the real world.

Posted in Swampland, This Week's Hype | 13 Comments

John Tate 1925-2019

Posted on October 20, 2019 by woit

John Tate, who was responsible for some of the most important developments in number theory and arithmetic geometry during the second half of the twentieth century, has passed away at the age of 94. Tate was a faculty member in the Harvard math department when I was an undergraduate there, moving on to UT Austin in 1990, then retiring from there in 2009.

The work that Tate is famous for includes “Tate’s thesis”, his 1950 doctoral thesis, which may be the most influential doctoral thesis of modern mathematics. For a book-length explanation of Tate’s thesis, see Ramakrishnan and Valenza’s Fourier Analysis on Number Fields. The later generalization of the GL(1) case of Tate’s thesis to the non-abelian GL(n) case is one of the founding pillars of the Langlands program.

Tate was the Abel Prize laureate in 2009, and one can learn a lot more about him from an interview conducted around the time of the award. For an extensive discussion of Tate’s mathematical work, see this article from James Milne, or this review by Milne of Tate’s Collected Works.

From Milne’s web-site, some stories about Tate:

A mathematician was explaining his work to Tate, who looked bored. Eventually the mathematician asked “You don’t find this interesting?” “No, no” said Tate, “I think it is very interesting, but I don’t have time to be interested in everything that’s interesting”.

As a thesis topic, Tate gave me the problem of proving a formula that he and Mike Artin had conjectured concerning algebraic surfaces over finite fields. One day he ran into me in the corridors of 2 Divinity Avenue and asked how it was going. “Not well” I said, “In one example, I computed the left hand side and got p13; for the other side, I got p17; 13 is not equal to 17, and so the conjecture is false.” For a moment, Tate was taken aback, but then he broke into a grin and said “That’s great! That’s really great! Mike and I must have overlooked some small factor which you have discovered.” He took me off to his office to show him. In writing it out in front of him, I discovered a mistake in my work, which in fact proved that the conjecture was correct in the example I considered. So I apologized to Tate for my carelessness. But Tate responded: “Your error was not that you made a mistake — we all make mistakes. Your error was not realizing that you must have made a mistake. This stuff is too beautiful not to be true.”

During a seminar at Harvard, a conjecture of Lichtenbaum’s was mentioned. Someone scornfully said that for the only case that anyone had been able to test it, the powers of 2 occurring in the conjectured formula had been computed and they turned out to be wrong; thus the conjecture is false. “Only for 2” responded Tate from the audience. [And, in fact, I think the conjecture turned out to be correct except for the power of 2.]

Tate’s father, John Torrence Tate Sr., was a physicist, editor of the Physical Review between 1926 and 1950. In one famous story, Tate Sr. stood up to Einstein by insisting that one of his papers be refereed in the usual way. Einstein was outraged (but it turned out the paper was incorrect). A few years ago I was at a talk here in New York at the Simons Foundation, during which the speaker put up a slide referring to Tate (Jr.)’s work, with a picture of Tate. After a moment, from the back of the room we heard “that’s not me, that’s my father!”.

Update: Kenneth Chang has an obituary of Tate at the New York Times.

Posted in Obituaries | 1 Comment

Foundations

Posted on October 11, 2019 by woit

Some links related to the foundations of math and physics:

  • Kevin Hartnett at Quanta has a long article on Jacob Lurie and his work on infinity categories. Unfortunately Lurie didn’t participate in the article himself, so comments are only from others. The article does a good job of giving at least a vague sense of what these very abstract foundational ideas are about, as well as examining the math community’s struggle to absorb them. Lurie’s work on this is spread out over more than 900 pages here and more than 1500 pages here. Recently he has been putting together an online textbook/reference version of this material as Kerodon, which is modeled after and uses much of the same software as Johan de Jong’s Stacks project.
  • At Mathematics without Apologies, Michael Harris has some comments on a recent discussion of the Mechanization of Math, held here in New York at the Helix Center. A video of the discussion is available here.
  • In the new (November) issue of the AMS Notices John Baez has a review of a recent collection of articles about the foundations of mathematics and physics. The book, Foundations of Mathematics and Physics One Century After Hilbert, contains contributions about both math and physics, although in his review Baez concentrates on issues related to physics. He notes “The elephant in the room is string theory.”
    The same issue of the Notices contains an informative long article about Michael Atiyah and his career, written by Alain Connes and Joseph Kouneiher (Kouneiher is the editor of the book reviewed by Baez).
Posted in Uncategorized | 6 Comments

2019 Physics Nobel Prizes Announced, John Horgan Wins

Posted on October 8, 2019 by woit

The 2019 Physics Nobel Prizes were announced this morning, half going to Jim Peebles for his work on big bang cosmology, half to Michel Mayor and Didier Queloz for discovery of an exoplanet.

You can read elsewhere more details about the prize winners and their work, but I do want to point out that this announcement means (since there will be no further Physics Nobel Prize awards before the start of 2020) that John Horgan has won his 2002 bet with Michio Kaku, with \$2000 going to the Nature Conservancy. The winning prediction from Horgan was:

By 2020, no one will have won a Nobel Prize for work on superstring theory, membrane theory, or some other unified theory describing all the forces of nature.

If one looks at the comments back then, Gordon Kane signs on to an even stronger variant of the Horgan/Kaku bet:

By 2020 there will be a Nobel Prize for a string- or unification- or supersymmetry-based theory or explanation or experimental discovery.

Luckily for him he doesn’t seem to have put up any money for this, since he has now lost this bet.

For my own comments at the time, see here (this was a couple years before this blog was started). As I explained there, I was willing to sign up on Horgan’s side of the bet if the “other unified theory” clause was eliminated. Unlike Horgan, I’m not a sceptic at all of the existence of a unified theory, or of humanity’s ability to find it. My argument (which I think has held up well) was that we’re not going to get there by pursuing superstring theory or anything like it. In a better world, the LHC would have found not a vanilla Higgs, but something unexpected that gave us a new idea about electroweak unification, one that pointed to a successful new idea about a fully unified theory. I didn’t think this was likely, but I thought it was possible, and I wasn’t interested in betting against the possibility I would most like to have seen.

What shocks me about where we are now that Kaku and Kane have lost their bets is not that they lost, which was to be expected, but that this loss seems to have had zero effect on their behavior. Kane’s endless replacement of failed predictions by new ones is a well-known story. For Kaku, one can get some idea of his current point of view from this interview:

Yahoo News: So tell us about your work in string field theory. You’re trying to finish Einstein’s equation?

Michio Kaku: That’s right. We want to find the “God Equation” — the ultimate theory that explains the entire universe. We want an equation that’s maybe 1 inch long that would allow us to “read the mind of God” — those are Einstein’s words.

Yahoo News: And how’s it going?

Michio Kaku: We think we have it! It’s called string theory. It’s not in its final form, and it’s not testable yet, [but] we have the Large Hadron Collider outside Geneva.

We’re testing the periphery of the theory, but the theory itself is a theory of the universe — so it’s very hard to test. But we physicists are optimistic. We think we will be able to test the theory. And we think it is the final theory. So physics ends at that point. Another era opens up, but one era ends when we finally prove this is the Theory of Everything….

If string theory is correct, it means that all the subatomic particles — the electrons, the protons — are nothing but musical notes on a tiny vibrating rubber band. So that physics is nothing but the harmonies of the vibrating rubber bands. Chemistry is nothing but the melodies you can create from the vibrating strings. The universe is a symphony of strings.

And the mind of God is cosmic music resonated through hyperspace.

Kaku also appears in this recent story, which Sabine Hossenfelder refers to as “math fiction”. For this kind of phenomenon I prefer Horgan’s version: “science fiction in mathematical form”.

I don’t know of other bets on string theory, but there were quite a few bets about SUSY. I assume David Gross has now paid off his lost bets on SUSY, haven’t heard though anything about that. At the Copenhagen SUSY bet event, the losers (Arkani-Hamed, Gross and Shih) showed no signs that losing a bet on a scientific outcome had any effect at all on these scientist’s views on the issue they were willing to bet on.

Update: Horgan has posted his own take on this here.

Posted in Uncategorized | 25 Comments

Various and Sundry

Posted on October 7, 2019 by woit

Various HEP-related links:

Update: Wired describes job opportunities for physicists and astrophysicists in the fashion industry.

Posted in Uncategorized | 6 Comments

Salam: The First ****** Nobel Laureate

Posted on October 3, 2019 by woit

This evening I noticed that a recent documentary about Abdus Salam, entitled Salam: The First ****** Nobel Laureate, has just appeared on Netflix, and I spent some time watching it. The title is a reference to Salam’s membership in the Ahmadiyya sect of Islam, which in Pakistan has been declared heretical, and thus Salam not Muslim.

I enjoyed watching the film, and learned a lot I didn’t know about Salam, but there’s not a great deal in the film about his actual work in theoretical physics. While starting to write more here about the film based on some notes I took while watching it, I noticed that Matin Durrani last year at Physics World wrote an excellent detailed review of the film, and I recommend you consult that for more details.

Among those interviewed are Chris Isham and Michael Duff, who have interesting comments on what it was like to work with him. I was pleased to see that one old photograph had him standing in front of a blackboard that prominently featured “Unitary G-reps”.

Update: For another detailed review of the film, see here.

Posted in Film Reviews | 5 Comments

Various and Sundry

Posted on September 26, 2019 by woit

A couple of mathematics items:

  • Photographer Jessica Wynne has been taking photographs of mathematician’s blackboards, and there’s a story about this in the New York Times. Many of her photographs have been taken here at Columbia, where we happen to have, besides some excellent mathematicians, also some excellent blackboards.
  • A non-Columbia excellent mathematician I’ve sometimes written about here is Bonn’s Peter Scholze. If you want to get some idea of the field he works in (arithmetic geometry) and what he has been able to accomplish, a good place to learn is Torsten Wedhorn’s new survey article On the work of Peter Scholze.

On the string theory front:

  • Arguments about the failure of string theory as a unified theory have been going on so long that they are now a topic in the history of science. For detailed coverage of many events in the long history of these arguments, you can consult historian of science Sophie Ritson’s 2016 University of Sydney doctoral dissertation. It and some of her other work is available at her academia.edu website.
  • For the latest in content-free argumentation about the failure of string theory unification, Steve Mirsky has a podcast discussion with string theory fan Graham Farmelo (see discussion of his recent book here), in which Mirsky challenges Farmelo about the problems of string theory. Farmelo has spent a lot of time at the IAS and basically takes the attitude that the point of view of certain unnamed string theorists there is what should be followed. I’d describe it as basically “we’ve given up working on string theory unification, but will keep insisting it is the best way forward until someone proves us wrong by coming up with a completely successful alternate idea.”
  • For the absolute latest attempt to extract some sort of “prediction” from string theory, see this week’s Navigating the Swampland conference in Madrid. Today there was a discussion session, with results shown of a survey of the views of those attending the conference. Note that, on the contentious topic of the reliability of supposed metastable de Sitter solutions of string theory, the Stanford group defending this reliability does not seem to be represented at the conference. I’ve been trying to understand what picture of physics this research has in mind, given that one main goal is to torpedo the metastable de Sitter solutions, and thus the usual “anthropic string landscape” picture. Looking at page seven, most participants seem to want to replace single field inflation models with more complicated quintessence or multi-field inflation models.
    In Hirosi Ooguri’s talk he gives a supposed “unparalleled opportunity for string theory to be falsified”, I gather by claiming string theory somehow implies a small value of r. He quotes Arkani-Hamed as saying that string theorists should have reacted to the bogus BICEP2 measurement of r=.2 by saying “if this is true string theory is falsified.” They didn’t do that. When the topic came up at the time, what they had to say was:

    Theoretical physicist Eva Silverstein of Stanford says she disagrees that string theory-based models of inflation are in any sort of trouble. “There is no sense in which we are forced to start over,” she says. She adds that in fact a separate class of theories that involve both axions and strings now look promising.

    Linde agrees. “There is no need to discard string theory, it is just a normal process of learning which versions of the theory are better,” he says.

Update: Some more math

Several physicists now have pieces up explaining why Sean Carroll’s claim that “the Multiverse did it” (i.e. all you have to do is believe in multiple worlds) isn’t a real solution to the measurement problem. Beside the previously mentioned Chad Orzel, there’s also Sabine Hossenfelder and Philip Ball. I agree with Ball’s conclusion:

Here, then, is the key point: you are not obliged to accept the “other worlds” of the MWI, but I believe you are obliged to reject its claims to economy of postulates. Anything can look simple and elegant if you sweep all the complications under the rug.

Update: A video of the discussion session at the Swampland conference is here. It seems that I’m not the only one confused about what assumptions people working on this are making and what they are or are not accomplishing.

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