Prizes and Other Stuff

Posted on October 15, 2015 by woit
  • There will be an awards ceremony November 8 for the 2016 Breakthrough Prizes, hosted by Seth MacFarlane, and airing live on the National Geographic Channel, later to run on FOX. The next day at Berkeley there will be a Breakthrough Prize Symposium, featuring talks by the winners and others.

    In physics the prizes to be awarded include the big $3 million prize and up to three $100,000 prizes for young researchers. The symposium physics schedule lists as speakers “2016 Breakthrough Prize Laureates”, with the plural perhaps a hint that more than one person will be sharing the $3 million. The first three rounds of these mostly went to string theorists but there seems to have been some sort of policy change last year (the award went to Supernova observations indicating an accelerating cosmology). I have no idea at all who they’ll choose this year. The theorist speakers discussing the future of the subject at the symposium are Arkani-Hamed, Hall and Bousso, a clean sweep for multiverse mania.

    On the mathematics side, there’s also a $3 million prize and up to three $100,000 prizes. The symposium schedule lists “2016 Breakthrough Prize Laureate”, so maybe a hint there’s just one in math.

  • In other news on the prize front, the APS will now be awarding a Medal for Exceptional Achievement in Research, with the first one going to Edward Witten.
  • The Wall Street Journal has published a response to the Gross/Witten piece advocating a Chinese “Great Collider”. Physicist Jonathan Katz describes particle physics as a “dying”, “moribund” subject. He argues that research funding should go to “tabletop experiments”, like for instance the ones he does.
  • The new AMS Notices is out, with a piece by Loring Tu on the origin of the theorem due to Atiyah-Bott often known as the Woods Hole Fixed Point Theorem. Tu does a great job of explaining this beautiful mathematics, as well as the details of the controversy over Shimura’s role in sparking this by a conjecture. He doesn’t much discuss Shimura’s memoir, which I wrote about here, which includes the claim that Serre attacked him out of jealousy about Shimura’s conjecture. I’ve never really understood Shimura’s point of view on this, since usually mathematicians value theorems over conjectures, and it is clearly Atiyah-Bott who had the theorem here.
  • From David Mumford’s blog I learned about an experimental neurobiology paper co-authored by Atiyah. It is quite interesting, but even more interesting is the blog entry by Mumford that it inspired. Mumford is one of the greats of algebraic geometry, and he gives a fascinating characterization of the different sorts of ways in which mathematicians pursue research. Mathematics done at the highest level involves strikingly different personalities and research strategies, which Mumford characterizes as four different tribes: “explorers”, “alchemists”, “wrestlers” and “detectives”. If you’re at all interested in how mathematics research is done, this is highly recommended reading.
  • Also recommended, if you’re interested in the overlap of physics and philosophy, is a new piece by Massimo Pigliucci on String Theory vs. the Popperazi.
Posted in Uncategorized | 14 Comments

This and That

Posted on October 7, 2015 by woit
  • The Perimeter Institute’s public lecture series tonight will feature Neil Turok on The Astonishing Simplicity of Everything. I think Turok is one of the few theorists speaking to the general public who has got the story of the current situation right: the LHC and CMB results point to the Standard Model + simple model of cosmology, ruling out many of the complicated models that have enthralled theorists for decades. By all rights, this should change the behavior and attitudes of theorists, I hope talks like his will have an effect. In any case, it should be vastly better than the last one of these, devoted to a misleading sales job for a failed theory.
  • Nature magazine has a very good piece by Davide Castelvecchi on Shinichi Mochizuki and his impenetrable proof. It gives an accurate picture of the current situation: still virtually no experts have been able to understand Mochizuki’s claims well enough to evaluate whether he has a valid proof. One counter-example is Ivan Fesenko, who is organizing a December workshop that may clarify the situation.
  • The big news this week is the physics Nobel for the discovery of neutrino masses. I haven’t written about this partly because I’m pretty ignorant about the history of the experiments awarded the prize (or, more accurately should have gotten the prize, not just a single person from the experiment), and the web is full of well-written coverage of this. The issue of the theory of neutrino masses is a fascinating, but quite intricate one, and some day I hope to write a bit about it, but lack the time right now.
  • Tommaso Dorigo has a posting here about the great Italian theorist Guido Altarelli, who passed away last week.
  • At some point I came across a list of the top donors to US political campaigns and was a little bit surprised to see that Jim Simons was on it, at number 7. I also noticed that someone else at his hedge fund spends even more on politicians than Simons does: Robert Mercer, a computer science Ph.D., is at number 4 (better informed people have pointed out to me that these numbers only include some publicly reported categories of donations). The Washington Post has a profile on Mercer today, which explains that he’s one of the people we have to thank for Ted Cruz (Mercer is the top donor in the US to 2016 presidential campaigns, according to this).

    In terms of funding politicians and science, increasingly it’s the hedge fund guy’s world, we just live in it. I’m a big fan of much of what the Simons Foundation does, less so of Mercer’s science funding, which goes to the Oregon Institute of Science and Medicine. The people there seem to be interested in climate denialism, surviving nuclear attack, and getting ahold of your urine.

    Physicists and mathematicians don’t always have huge success in the hedge fund business. Robert Stock, a physics Ph.D from Carnegie-Mellon, seems to have gone from trying to blow up missiles with lasers to instead having more success blowing up a hedge fund, Spruce Alpha.

Update: According to today’s New York Times, for the 2016 presidential election cycle, Mercer is the number two donor in the US, at 11.3 million. Simons is way, way down the list at 550,000. Their list of donors is heavily dominated by the financial industry (64 individuals or families), with the next largest number from the oil and gas industry (17 individuals or families).

Posted in Uncategorized | 28 Comments

Oddities

Posted on October 2, 2015 by woit

A few odd things that I’ve run into recently:

  • The IAS has a weekly meeting to discuss current topics in HEP theory. From their events calendar, next week’s meeting will be devoted to “The Cosmological Constant and the String Landscape”, with suggested readings the 28 year old papers by Weinberg on anthropics and the CC, as well as the KKLT paper (I’m a fan, see here) and its Bousso/Polchinski predecessor from about 15 years ago. I would have thought this was a very well-worn topic. The one recent reference is a defense by Polchinski of KKLT against some technical challenges, but if the intent is to discuss those, it’s unclear why they’re not in the references (and they have nothing to do with Weinberg/CC/anthropics).
  • Mochizuki has two new things on his website. One is a long discussion of the use of the words “anabelioid” and “Frobenioid”, the other is an animated video of a diagram explaining a theorem (see near bottom of here).
  • A couple years ago there was a controversy over the proof of the so-called “Yau-Tian-Donaldson” conjecture (see here), with Donaldson and his collaborators publicly complaining about Tian’s paper claiming credit for proof of this conjecture. The Tian paper was submitted to the Courant journal Communications on Pure and Applied Mathematics in February 2013, was published there in the July 2015 issue (a technical corrigendum appeared a couple weeks ago). More expertise than I have would be needed to see if the published version addresses the Donaldson et al. concerns, a quick look doesn’t indicate evidence of that.

    At the time I wrote:

    On a more positive note, perhaps this controversy will not interfere much with future progress in this area, as Donaldson and Tian are jointly organizing a Spring 2016 workshop on this topic at MSRI.

    The MSRI directory for this year though lists Tian as visiting, but not Donaldson.

  • Among the many oddities associated with string theory is the decision of a group in Philadelphia to name a group of charter schools there the String Theory Schools. I don’t think they teach string theory, just liked the name. The financing of these schools is now attracting controversy. It seems they are running into some financial trouble, involving huge real estate deals and tax-exempt bond financing. For the details of the story, see here. For some analysis, see a Naked Capitalism piece: Private Equity Asset-Stripping Strategy Meets Charter Schools to Produce Even Better Looting.
  • Presidential candidate Ben Carson has been widely (and quite appropriately…) criticized for some of his odd and non-sensical views about science. In USA Today’s factcheck piece about this, we’re told

    Carson went on to claim that the presence of stars and planets is related to the existence of multiple Big Bangs that eventually might produce an ordered universe:

    Carson: And then they go to the probability theory, and they say “but if there’s enough big bangs over a long enough period of time, one of them will be the perfect big bang and everything will be perfectly organized.” And I said, so you’re telling me if I blow a hurricane through a junkyard enough times over a long enough period of time after one of them there will be a 747 fully formed and ready to fly?

    That is not an accurate reflection of the Big Bang theory. Though some theories of the origin of the universe suggest that the Big Bang was only one of many such explosions, these theories do not state that the currently ordered existence is a spontaneous result of one of these repeated Big Bangs.

    He’s getting it somewhat wrong, but this does sound a lot like Carson has been reading about the string theory multiverse…

Update: Please do not use the reference to Carson as an excuse to post your thoughts on US politics and the ongoing political campaign. I think everyone would appreciate not having to be subjected to that topic here.

Posted in Uncategorized | 20 Comments

The Free Particle

Posted on September 29, 2015 by woit

Following on my notes about Euler’s formula, I’ve finally finished some work on another piece of elementary exposition, a discussion of the free quantum particle, which can be found as chapters 10, 11 and 12 of the book I’m working on.

These chapters are a complete rewrite and major expansion of what used to be there, a rather slap-dash single chapter on the subject. The excuse for this in my mind had been that it’s a topic treated in detail in every quantum mechanics textbook, so best if I passed over it quickly and moved on to things that weren’t so well treated elsewhere. Another reason for this was that my understanding of analysis has never been what it should be, and it seemed best if I not make that too obvious by how I handled the mathematics of this subject.

This summer I started rewriting the book from the beginning, and once I hit the chapter on the free particle it became very clear that it needed improvement, both for its own sake and for how the material was needed in later chapters. I spent some time doing some remedial study in analysis, and after a while got to a point such that I felt capable of writing something that captured more of the relevant mathematics. Finally, today I got to the point where these three chapters are in decent shape, and soon I’ll move on to later ones.

One thing that I’d never thought much about before, but that struck me while rewriting these chapters, is the quite peculiar nature of a position eigenstate in quantum mechanics. Normally one only thinks about this in relativistic quantum field theory, where the problems associated with localizing a relativistic particle motivate the move to a quantum field theory. Of course a position eigenstate is just a delta-function, but what is peculiar is the dynamics, what happens if you take that as an initial condition. See the end of chapter 12 for what I’m talking about (be sure you have the latest version, today’s date on the front), I won’t try and reproduce that here. Part of this story is the tricky nature of the free-particle propagator in real time, as opposed to its much better behavior in imaginary time. The issue of analytic continuation in time continues to fascinate me, including the quite non-trivial nature of what happens even for the supposedly trivial case of a free particle in one spatial dimension.

Posted in Quantum Mechanics | 19 Comments

Visions of Future Physics

Posted on September 22, 2015 by woit

There’s a great profile of Nima Arkani-Hamed by Natalie Wolchover just out at Quanta magazine, under the title Visions of Future Physics. I recently linked to another profile of him from the IAS, which covers some similar ground.

He’s often been a topic of postings here, and the profile explains why, with his colleagues describing him as the “messiah”, “Pied Piper” and “impresario” of high energy physics.

“He keeps coming up with the goods, and his persuasiveness is hypnotic,” said Raman Sundrum, a theoretical physicist at the University of Maryland in College Park, “so a lot of people follow where he leads.”

I’ve often marveled at his performances, with his talks sometimes a unique mixture of brilliance, insight, and over-the-top outrageous indefensible claims (his talk here last week was uncharacteristically restrained). As an example of the genre, the IAS profile includes:

“It is extremely interesting to think about getting sophomores up to the speed of a second-year graduate student. I think it is possible,” says Arkani- Hamed.

which is simultaneously quite inspirational and, well, nuts.

A couple years ago I was struck by a talk of his in which he showed a lot of self-knowledge, describing himself as an “ideolog” (see here). There’s more about this in the Quanta profile:

“It’s important for me while I’m working on something to be very ideological about it. And then, of course, it’s also important after you are done to forget the ideology and move on to another one.”

The ideologies on display this time include a very speculative picture of a future union of mathematics and theoretical physics:

Ultimately, he said, anywhere from 10 to 500 years from now, the amplituhedron and these cosmological patterns will merge and become part of a single, spectacular mathematical structure that describes the entire past, present and future of everything “in some timeless, autonomous way.”…

There is a mathematical proof, Arkani-Hamed observed, that all algebraic numbers can be derived from configurations of a finite whole number of intersecting points and lines. And with that, he expressed a final conjecture, at the end of a long, cerebral day, before everyone else went home to bed and Arkani-Hamed headed to the airport: Everything — irrational numbers, along with particle interactions and the correlations between stars — ultimately arises from possible combinatorial arrangements of whole numbers: 1, 2, 3 and so on. They exist, he said, and so must everything else.

Personally, I don’t think this is going to work out, but he’s right that people need a vision to pursue, to drive them forward in finding new things. Unless he gets a lot further with it, I don’t think this one is going to get so much interest as to drive out other ideas, especially from mathematicians interested in physics, who have other competing visions.

Where Arkani-Hamed has become a really problematic ideolog, one endangering the health of the subject, is in his insistence on “naturalness” as the central question of HEP theory at the TeV scale, coupled with the ideology that if the LHC doesn’t see new “natural” physics at the TeV scale, then the intellectual suicide of the multiverse is all HEP theory has to look forward to. He’s been pushing this ideology, hard, for quite a while now, and I think it’s long past time for him to take his own advice and “forget the ideology and move on to another one.”

Much of the article is about his efforts to push forward a Chinese plan to build a next-generation collider. Perhaps his great enthusiasm will help move this project along (a book about it by Yau and Nadis, From the Great Wall to the Great Collider, will soon come out). It raises all sorts of difficult issues for the future of experimental HEP, including that of the future of CERN, issues that will play out over many years (timelines for things like this are generally wildly over-optimistic, and here people are talking about 2042). Framing the case for a 100 TeV machine as “1% fine-tuning evidence for the multiverse from the LHC wasn’t convincing, even though we said it would be, so we need a bigger machine to get .1% fine-tuning evidence” is something that I think isn’t going to fly, no matter how enthusiastically presented. In the article Kyle Cranmer makes the point that .1% tuning versus 1% tuning means little:

“I am very sympathetic to the idea that this is a critical point in the field and that naturalness/fine-tuning is a deep issue,” he wrote in an email. “However, I’m not convinced that if we built a 100-TeV collider and saw nothing that it would be conclusive evidence that nature is fine-tuned.” There would remain the nagging possibility that a natural completion of the Standard Model exists that a collider simply can’t access.

and Jester

argues that if no new particles are found at 100 TeV, this will leave physicists exactly where they are now in their search for a more complete theory of nature — clueless.

I think David Gross has it right:

Gross, who considers naturalness a murky concept, simply wants a last-ditch search for new physics. “We need more hints from nature,” he said. “She’s got to tell us where to go.”

The case for mankind to embark on a new project to push forward the boundaries of science is the same as it has always been: even though it’s expensive and difficult, we should do it because we’ll see how the world works at an even smaller distance scale. Just possibly we’ll learn enough to understand how to improve the Standard Model and achieve an even deeper insight into the physical universe.

Update: Gross and Witten have an editorial today in the Wall Street Journal (as usual with the WSJ, try Googling the article to get around their paywall), supporting the idea of a Chinese Great Collider project.

Posted in Uncategorized | 49 Comments

Connes on the Riemann Hypothesis

Posted on September 21, 2015 by woit

There’s a fascinating new preprint out from Alain Connes, called An essay on the Riemann Hypothesis, written for a volume on “Open Problems in Mathematics”. Evidently the late John Nash is an editor, and responsible for commissioning this piece.

Connes is a mathematician of the first rank, and a very original one at that. He has now struggled with the Riemann hypothesis for many years, and his account of various approaches to the problem and the state of efforts to pursue them is a remarkable document of a sort that too rarely gets written.

Much of what he is concerned with is the question of how to find a proof along lines related to those used to prove the analog of the Riemann hypothesis in the case of function fields (this was successfully carried out by Deligne in the early 1970s). James Milne has a wonderful expository piece on the topic of this proof, going into details of the history and the mathematics. It provides a great supplement to the more speculative article by Connes.

For something much more concrete about the Riemann hypothesis, there’s a new book by Barry Mazur and William Stein, Prime Numbers and the Riemann Hypothesis. Among a long list of attempts to relate this to physics, there’s an interesting relatively recent discussion of one idea from John Baez.

Posted in Uncategorized | 3 Comments

Various and Sundry

Posted on September 14, 2015 by woit

The semester here is finally underway, and I’m getting back to work on my quantum mechanics and mathematics book (latest version available here). Current plan is to have a final version by next spring, with publication by Springer late next year. This semester I’m teaching Calculus II, a subject where there’s only one thing I really dislike about pretty much all textbooks, their refusal to use Euler’s formula. Since I couldn’t find an online source I was completely happy with, I spent some of the last couple days writing up some notes for the students on Euler’s Formula and Trigonometry, which maybe someone else will find useful. In other news:

  • Nima Arkani-Hamed was here today, giving a talk on a new model he calls “NNaturalness”. The basic idea is to consider something like N copies of the Standard Model, with N a large number. Large N fixes the technical naturalness problem, with something like N=104 fixing the MSSM’s current naturalness problem, and N=1016 fixing the non-supersymmetric problem. He makes clear that he’s well aware that this is a pretty contrived thing to do, but argues that it’s interesting one can do this while evading dramatic disagreement with experiment, and coming up with potential CMB signatures soon observable (e.g. the effective number of relativistic degrees of freedom).

    He has a nice description of the naturalness problem as “in any theory where we can compute the mass of the Higgs it has a fine-tuning problem”. Probably there are people out there who think they have a way to compute the Higgs mass who would disagree with him. To me the problem is that the theories he’s talking about (GUTs, string landscape) don’t actually explain anything about the underlying physics of electroweak symmetry breaking (where does the Higgs field come from and why does it have those couplings?). Given this, it’s unclear why one should worry about the fine-tuning.

    He describes the landscape and the multiverse as “like democracy, the worst idea except for everything else”, and gives a defensive argument for why one should study alternatives like “NNaturalness”, even if they’re not as good as the multiverse (which he finds “simple and deep”). To him it’s worth thinking about alternatives to the multiverse (as a “foil”) not because the multiverse is untestable pseudo-science, but because maybe one shouldn’t just give up. So, it seems that at this point he’s not quite signing up with the intellectual suicide of multiverse mania, although he sees it as the most attractive path available.

    In other Arkani-Hamed news, the IAS has an article about his activities promoting a next generation collider here.

  • The KITP has a newsletter here, including a description by Graham Farmelo of his visit there. Oddly, no matter what he writes about, Farmelo almost always includes an unconvincing defense of string theory and/or the current activities of string theorists (for examples, see here, here, here and here). In this case he assures us that the KITP theorists are not given to “mathematical adventurism”. I think he’s right, but that’s the problem…
  • Someone pointed me recently to Olivia Caramello’s web-page on Unifying theory and her arguments with fellow category theorists. I had a youthful infatuation with category theory, but ultimately came to the conclusion that there’s a real danger in that kind of “unification” of going too far in the direction of saying less and less about more and more. Many of the ideas involved are powerful and attractive, but the remarkable thing about mathematics is that, even for the lover of grand ideas, less generality is sometimes even more so.

Update: One more. If you’re in the Bay Area next week, you might want to head up to MSRI for a series of elementary talks on the Langlands program by Edward Frenkel.

Posted in Multiverse Mania, Uncategorized | 63 Comments

This Week and Next Week’s Hype

Posted on September 3, 2015 by woit

This week’s hype comes to us from Discover Magazine, which has Is Our Universe One of Many? Here’s How We Can Find Out. Needless to say, the author doesn’t actually tell us how we can find out, just repeats the usual “maybe we’ll see bubble collisions” argument often discussed here. We’re also told that

It is important to keep in mind that the multiverse view is not actually a theory, it is rather a consequence of our current understanding of theoretical physics.

It seems that our “current understanding of theoretical physics” is the string theory landscape. If you ask what the evidence is for string theory, you’ll be given the usual circular reasoning that we don’t have evidence because of the multiverse.

For next week’s hype, there will be a promotional public talk in Paris next Tuesday entitled String Theory: results, challenges and magic. Presumably this will be much the same as the speaker’s String theory: results, magic and doubts from two years ago. The argument for string theory seems to be that it is “magic”, and somehow in the past two years the “doubts” have turned into “challenges”. The abstract describes string theory poetically as having

soured and captured the imagination of a generation of high energy physicists.

which I would say is a deep truth, if probably not one the speaker intended.

Posted in Multiverse Mania, This Week's Hype | 29 Comments

SUSY 2015

Posted on August 29, 2015 by woit

SUSY 2015, this year’s version of the big annual conference on supersymmetry, has been going on for the past week at Lake Tahoe. Joe Lykken began his summary talk by explaining how as a kid he was a big fan of the Bonanza TV show, about a ranch along the shores of Lake Tahoe. He always wanted to travel to Lake Tahoe and visit the Ponderosa ranch, was bitterly disappointed when he finally got to Lake Tahoe and found that the Ponderosa did not exist. The relevance of the story to his talk is “left as an exercise for the audience”, with a hint in the next slide, which gives the executive summary of the search for SUSY at the LHC: “We haven’t found it.” He ends the summary talk with this now well-known prediction for the SUSY 2215 conference.

In his discussion of “naturalness” (see slide 25), he makes what to me has always been an obvious point, but I haven’t seen it made ever at a conference like this:

Is the Standard Model (almost) all there is?

Maybe the naturalness argument applied to the Higgs is just wrong (well, it was apparently wrong for the vacuum energy too)

The Standard Model plus some TeV scale renormalizable additions (like dark matter) might be all there is

The Standard Model itself, or with such modest additions, is completely natural (EW scale is not a prediction)

Usual counterargument involves the putative Planck scale and unification thresholds, but this is speculative

An unsatisfying scenario, leaving many questions unanswered, but has a certain minimalist appeal

Some of the other talks included:

  • Nima Arkani-Hamed’s slides and title aren’t available, but the Twitter coverage of the conference included a picture of one of his slides. This tweet reports that he announced that he was “rather annoyed” and “sick of thinking” about naturalness. I guess if you’ve spent most of your career arguing that the LHC would “resolve the naturalness problem” (because it would move fine-tuning from the Tevatron 10% to 1% if it saw nothing), gearing up now for an argument that a 100 TeV collider is needed to “resolve the naturalness problem” (by going from 1% to .1%) would be kind of annoying… In the slide he makes the same argument as in Particle Fever: no SUSY means particle theory should commit suicide and embrace the multiverse.
  • In Gordon Kane’s talk he gave his latest string theory-based predictions for the masses of superpartners. For the last twenty years or so, his gluino mass prediction has always been the same: just a little bit higher than the current bounds. These bounds however keep moving up, so his prediction has moved from 250 GeV in 1997 to 1.5 TeV today (“Detectable soon”!). I think one very solid prediction that one could make is that Kane’s SUSY 2016 gluino mass prediction will be 2 TeV.
  • Joe Polchinski’s talk defended moduli stabilization schemes such as the KKLT one that came out of his original work with Bousso, ending with the claim that

    The KKLT construction has been thoroughly vetted, and it seems to me has survived robustly.

    The de Sitter vacua are still there, as is the landscape.

    Besides his pre-KKLT role in moduli stabilization, Polchinski is one of the most prominent exponents of the idea that particle theorists should just give up, using the KKLT moduli-stabilized string vacua as a reason for why string theory can never be tested, but we should believe it anyway. He’s been promoting this heavily since 2004, when he got Scientific American to publish this article with Raphael Bousso. My take on that article seems to have upset him greatly, and had a lot to do with the arXiv policy of not allowing trackbacks to this blog (which continues to this day).

    This blog does seem to have played an odd role in the topic of Polchinski’s talk. Back in early 2014 someone wrote to me to suggest that I might want to discuss a series of papers by Bena, Grana et al. which pointed out problems with KKLT. I responded that I didn’t think this was a good idea: while I was no expert, it seemed to me that the KKLT construction was an absurdly complex one involving poorly controlled approximations (thus hard to conclusively decide if it was “right” or “wrong”), and it had entered the realm of ideology, as a bedrock for explaining why string theory could never predict anything. What I didn’t say was that I’m a fan of arguments showing string theory can never predict anything, so why should I publicize work challenging them?

    Later in 2014, the same person wrote to me again to suggest that I change my mind, that there was a new preprint about this. I weakened and mentioned it here. A couple months later Polchinski published this, which mounts a defense of KKLT against criticisms like those of Bena, Grana, et al. I didn’t know about this, but did write a long posting about another arXiv preprint he had posted the same day, which was about “dualities” in general, and which I found quite interesting. Only after he and Bousso appeared in the comment section to criticize me about KKLT did I realize that they saw me as responsible for promoting anti-KKLT views, not realizing that I’m actually a KKLT fan. Some strange things have happened over the years at this blog, that Christmas Eve discussion was right up there.

    In any case, just to make my views clear: I’m a big fan of KKLT, glad to hear that it now has been “thoroughly vetted”. Back when I first heard about it in 2003, I thought “this is great! now that string theorists have proved to themselves that their theory isn’t predictive, they’ll move on to something else”. I’ve been surprised though about how long that is taking to happen…

Posted in Multiverse Mania, Uncategorized | 36 Comments

This Week’s Hype

Posted on August 28, 2015 by woit

Bogus media stories about how “physicists finally find a way to test string theory” have now been with us for decades, with a large number of them documented here. Recently this phenomenon seemed to finally be dying down, with such stories the province of more obscure media outlets and the press offices of not very well-known institutions. Yesterday though saw a new example of the genre, coming to us from IAS faculty and the Fermilab/SLAC publication Symmetry, which announces that Theorists from the Institute for Advanced Study have proposed a way forward in the quest to test string theory.

The source of all this is the Arkani-Hamed/Maldacena paper Cosmological Collider Physics from earlier this year. As usual with a lot of these bogus stories about “testing string theory”, the work in question actually has nothing to do with string theory. It’s about possible ways to look for particle physics effects in subtle effects in non-Gaussianities in the CMB. This is a theoretically interesting topic, but suffers from the obvious problem that, experimentally, there are no non-Gaussianities in the CMB. The limits on non-Gaussianity from Planck and other CMB experiments are quite strong.

The connection to string theory is given in the article as:

But scientists are working out ways that experiments could at least begin to test parts of string theory. One prediction that string theory makes is the existence of particles with a unique property: a spin of greater than two.

This is of course complete nonsense, since there are plenty of known particles of spin greater than two. String theory arose as an attempt to explain some of these, but it turned out that it didn’t work, the actual explanation was QCD, a quantum field theory. The author seems to have gotten this argument from the following statement in the Arkani-Hamed/Maldacena paper:

Of course, if we were to detect the contribution of a spin 4 state in the non-gaussianity, it would be a strong indication of string theory during inflation, since we suspect that a structure like string theory follows when we have weakly interacting particles with spin s greater than 2.

Knowing that there is a spin 4 state up at the inflation or Planck scale would of course be quite interesting, but I don’t see any reason to believe that effective field theory would apply to it or that this would “of course” “be a strong indication of string theory”. This argument would actually make better sense at lower energy. I suppose you could claim that lots of work being done at the LHC is “a way forward in the quest to test string theory”, since any day it could lead to evidence for a new weakly interacting spin 4 state. That would of course be pretty silly, but less silly than this article.

Combined with the bogus “test”, the article includes a large helping of the usual promotional material, ending with a section on “The value of strings”. We’re told that

Witten and others believe that such successes in other fields indicate that string theory actually underlies all other theories at some deeper level.

“All other theories”???

Update: I should make clear that my comment about the strength of the limits on non-Gaussianities was about the quality of the experimental results, and my impression that there are not near-term prospects for doing much better. Depending on what models one is talking about, such results are often not strong constraints. A correspondent suggest this source for more information about all of this.

Posted in This Week's Hype | 10 Comments