Not Even Wrong

I’ve looked at the talks from a few of the HEP experiment and phenomenology summer conferences. If anyone can point me to anything interesting that I’ve missed, please do so. The lack of new physics beyond the Higgs at the LHC has left the field in a difficult state.

One conference going on this past week and next is the IAS PiTP summer program aimed at advanced grad students and postdocs. This year the topic is HEP phenomenology, and talks are available here. If you want to understand the conventional wisdom on the state of the subject, you can watch Nima Arkani-Hamed’s three and a half hour lecture (here and here) which he starts off by describing as on the topic “What the Hell is Going On?”.

A lot of the first part is historical, starting off with the Georgi-Glashow GUT and the arguments for SU(5) or SO(10) GUT unification first put forward 43 years ago. He then walks the audience through the sequence of steps theorists have taken to solve the problems of such models, after an hour ending up at the landscape, spending a half an hour promoting the anthropic solution to the CC and other problems. The second part of the talk is largely devoted to making the case for his favored split SUSY models, with anthropics and the landscape taking care of their naturalness problems. By the end of the three and a half hours, Arkani-Hamed admits that this scenario is not that convincing, while arguing that it’s the only thing he can see left that is consistent with the idea that theorists have been following a correct path since 1974:

It’s the only picture of the world that I know where everything that we learned experimentally and theoretically for the last 30 years has some role to play in it. But my confidence in it is not so super high, and I definitely think its worth thinking about completely radically different things.

The disadvantage to the trajectory of going with what works and then changing a little and changing a little is that you might just be in the basin of attraction of the wrong idea from the start and then you’ll just stay there for ever.

To me by now the evidence is overwhelming that HEP theory has been in the wrong basin of attraction for quite a while, and the overriding question is what can be done to get out of it. If you’re in the wrong basin of attraction, you need to get out of it by going back to the point where you entered it and looking for another direction. I think Arkani-Hamed is right to identify the 1974 GUT hypothesis as the starting point that led the field into this wrong basin. HEP theory has progressed historically by identifying new more powerful symmetry principles. The move in 1974 was to go beyond the SM symmetries by picking a larger gauge group, then breaking it at a very high energy scale with new scalar fields. The history of the last 43 years is that this idea isn’t a successful one: as this talk shows, it leads to an empty theory that explains nothing. Can one find different new ideas about symmetry that are more promising?

I’ve finally found some time to look around the web to see what has been happening at conferences this summer. In this blog post I’ll point to a few on the math/physics interface featuring interesting talks. This area now (I think it may be Greg Moore’s fault) has started to acquire the name of “Physical Mathematics”, to distinguish itself from old-school “Mathematical Physics”. At this point though I’d be hard-pressed to provide a useful definition of either term.

• Talks from last month’s 2017 Bonn Arbeitstagung are available here. This conference was in honor of Yuri Manin and supposedly devoted to Physical Mathematics (although I suspect some of the speakers might not realize that they are doing Physical Mathematics). Dan Freed and Jacob Lurie gave two characteristically lucid series of talks, well worth watching.

  A very active area of physics these days with significant overlap with mathematics (of the sort discussed by Freed) is the study of topological superconductors and other materials in which topology plays a large role. For an introduction to this topic, Davide Castelvecchi at Nature has a new article The strange topology that is reshaping physics.

• CERN has just finished running an institute on the topic of the Geometry of String and Gauge Theories. It included a colloquium talk by Greg Moore on d=4 N=2 Field Theory and Physical Mathematics. I’ve always been fascinated by the d=4 N=2 super Yang-Mills theory in its “twisted” topological version. The mathematics involved is deep and amazing, and it is frustratingly close to the Standard Model…
• Pre-string math 2017 was this past week, and String Math 2017 will be next week. All sorts of interesting talks at both of these, relatively few of which have much to do with string theory. That’s of course also true of Strings 2017, but I’ll write about that elsewhere.

Other suggestions of interesting mathematically related summer schools with talks available are welcome. On the physics side, please wait for a succeeding blog entry on that topic.

Some links to things that may be of interest:

• There’s an excellent article at FiveThirtyEight about the issue of publicizing math research, taking as example the Atlas of Lie Groups and Representations project (which will soon be having a workshop). This kind of thing generally gets no public attention, while at the same time, one of the results of this research arguably got too much public attention (see here).
• There’s a new \$1 million mathematics prize that will be awarded for the first time this fall, together with a $1 million physics prize that was awarded for the first time last year. This is called the Future Science Prize, and to get it you need to be working in China. Used to be a \$1 million prize was a big deal, now with the \$3 million Breakthrough Prizes, a mere million looks like small potatoes.
• Another way you could get a measly \$1 million would be to prove (or disprove) the Hodge conjecture. For some inspiration, see Burt Totaro’s new survey of progress on the Tate conjecture (blog entry here).
• 4 gravitons has a nice posting about work by Turok and others about complexified path integrals and cosmology. The issue of the relation between Euclidean and Minkowski signature QFT is one that I think has gotten far too little attention over the years. Now that I’ve finished writing a book with a QFT discussion that sticks to Minkowski space, I’m hoping to work on writing something about the relation to Euclidean space.
• There’s an interview with Nima Arkani-Hamed here. His talk at the recent PASCOS 2017 conference (real title is second slide “What the Hell is Going On?”) gives his take on the current state of HEP, post failure of the LHC to find SUSY. He’s sticking with his 2004 “Split SUSY” as his “Best Bet”. I’d like to think his inspirational ending claiming that the negative LHC results are forcing people to rethink the foundations of the subject, asking again the question “What is QFT?” reflects reality, but not sure I see much of that.
• This year’s LHC startup has been going well, with a new luminosity record already set, and 6 inverse fb of data already collected. For more, see here.
• Remember that “dark flow” that was supposed to be in the CMB data and evidence for the multiverse (see here)? Still not there, according to Planck (via Will Kinney).

Update: I’m sorry to hear the news of the untimely death of Maryam Mirzakhani, who was the first woman to win a Fields medal, awarded at the last ICM in 2014. Her work was described in detail at the time in this article by Curt McMullen.

Eva Silverstein has a new preprint out, entitled The Dangerous Irrelevance of String Theory. The title is I guess intended to be playful, not referring to its accurate description of the current state of string theory, but to the possibility of irrelevant operators having observable effects.

The article is intended to appear in the forthcoming Cambridge University Press volume of contributions to the Munich “Why Trust a Theory?” conference held back in December 2015. The impetus behind that conference was a December 2014 article in Nature entitled Scientific method: Defend the integrity of physics. In that article, Ellis and Silk explained the problems with string theory and with the multiverse/string theory landscape.

The organizing committee for the Munich conference was chaired by Richard Dawid, a string theorist turned philosopher who has written a 2013 book, String Theory and the Scientific Method. For a fuller discussion of that book, see the linked blog post. To oversimplify, it makes the case that the proper way to react to string theory unification’s failure according to the conventional understanding of the scientific method is to change our understanding of the scientific method. Much of the Munich conference was devoted to discussing that as an issue in philosophy of science.

One aspect of the Munich conference was that it was heavily weighted towards string theorists, with contributions from Dawid, David Gross, Joe Polchinski, Fernando Quevedo, Dieter Lust and Gordon Kane all promoting the idea that string theory was a success. Polchinski explained a computation that shows that string theory is 98.5% likely to be correct, going on to claim that the probability is actually higher: “something over 3 sigma” (i.e. over 99.7%). The only contribution from a physicist that I’ve seen that argued the case for the failure of string theory was that from Carlo Rovelli, see here. Silverstein’s article says that it was commissioned by Dawid for the proceedings volume, even though she hadn’t been at the meeting. I’m curious whether Dawid commissioned any contributions from string theory critics who weren’t at the meeting.

Silverstein begins her article explaining how physics at a very high energy scale can in principle have observable effects. This of course is true, but the problem with string theory is that, in its landscape version, it has a hugely complicated and poorly understood high energy scale behavior, seemingly capable of producing a very wide range of possible observable effects, none of which have been seen. The article is structured as a defense of string theory, without explaining at all what the serious criticisms of string theory actually are. The list of references includes 53 items, only one critical of string theory, the Ellis/Silk Nature article. Some of the arguments she makes are:

• It is sometimes said that theory has strayed too far from experiment/observation. Historically, there are classic cases with long time delays between theory and experiment – Maxwell’s and Einstein’s waves being prime examples, at 25 and 100 years respectively… One thing that is certainly irrelevant to these questions is the human lifespan. Arguments of the sort ‘after X number of years, string theory failed to produce Y result’ are vacuous.

  I think the comparison to EM or GR is pretty much absurd. For one thing it’s comparing two completely different things: tests of a particular prediction of a theory (EM or GR) that made lots of other testable, confirmed predictions to the case of string theory, where there are no predictions at all. More relevant to the argument over how long to wait for an idea to pay off is that the real question is not the absolute value of the amount of progress, but the derivative: as you study the idea more carefully, do you get closer to testable progress or farther away? I don’t think anybody can serious claim that, 33 years on, we’re closer to a successful string theory unification proposal than we were at the start, back in 1985. I’d argue that the situation is the complete opposite: we have been steadily moving away from such success (and thus entered the realm of failure).

• About supersymmetry Silverstein writes:
  

  In my view, the role of supersymmetry is chronically over-emphasized in the field, and hence understandably also in the article by Ellis and Silk. The possibility of supersymmetry in nature is very interesting since it could stabilize the electroweak hierarchy, and extended supersymmetry enables controlled extrapolation to strong coupling in appropriate circumstances. Neither of these facts implies that low-energy supersymmetry is phenomenologically favored in string theory.

  It is true that Silverstein has never been one of those arguing that the usual string theory scenarios with supersymmetry and 10 or 11 dimensions show that string theory is testable. See for instance her comment here back during a “String Wars” discussion in 2006. Her current take on whether string theory implies supersymmetry is just

  Much further research, both conceptual and technical, is required to obtain an accurate assessment of the dominant contributions to the string landscape.

  The problem with this is that there is no sign of any possibility of progress towards deciding if the string theory landscape implies low-energy SUSY or not (quite the opposite). If you give up the assumptions of SUSY and 10/11 dimensions, you give up what little hope you had of any connection with experiment. She doesn’t mention the LHC at all, especially not the negative results about supersymmetry and extra dimensions that it has produced. The significance of these negative results is not that they disconfirm a strong prediction of string theory, but that they pull the plug on the last remaining hope for connecting standard string theory unification scenarios to anything observable. Pre-LHC string theorists could make an argument that there was good reason to believe in electroweak-scale SUSY, that such a scenario fit in well with string theory unification, and that LHC discovery of SUSY would point a way forward for string theory unification. That argument is now dead. All that’s left is basically the argument that “maybe a miracle will happen and we’ll be vindicated” which in her version is:

  In principle one could test string theory locally. In practice, this would require discovering a smoking gun signature (such as a low string scale at colliders, or perhaps a very distinctive pattern of primordial perturbations in cosmology), and nothing particularly favors such scenarios currently.

• Silverstein’s main argument is basically that string theory is valuable because it leads to the study of models that have various observable signatures that people would not otherwise look for. One example here is supersymmetry, the study of which has had a huge effect on collider physics, strongly shaping the analyses that the experimentalists perform. She gives some detailed other examples from her field of cosmology, in particular about possibly observable non-Gaussianities.
  

  String theory participates in empirical science in several ways. In the context of early universe cosmology, on which we have focused in this article, it helped motivate the discovery and development of mechanisms for dark energy and inflation consistent with the mathematical structure of string theory and various thought-experimental constraints. Some of these basic mechanisms had not been considered at all outside of string theory, and some not quite in the form they take there, with implications for effective field theory and data analysis that go well beyond their specifics.

  I think this is the best argument to be made for “phenomenological” string theory research (as opposed to “formal” string theory, where there are other arguments). Yes, coming up with new models with unexpected observable effects is a valuable enterprise. If your speculative idea generates such things, that’s well and good. The problem though is how to evaluate the situation of a speculative idea that has generated a huge number of such models, none of which has worked out. At what point do you decide that this is an unpromising line of research, better to try just about anything else? Silverstein makes the argument that

  Whether empirical or mathematical, constraints on interesting regions of theory space is valuable science. In this note we focus on string theory’s role in the former.

  Since information theory is currently all the rage, it occurred to me that we can phrase this in that language. Information is maximized when the probabilities are equal for a set of outcomes, since one learns the most from a measurement in that case. The existence of multiple consistent theoretical possibilities implies greater information content in the measurements. Therefore, theoretical research establishing this (or constraining the possibilities) is directly relevant to the question of what and how much is learned from data. In certain areas, string theory plays a direct role in this process.

  The problem here is that of what is an “interesting region of theory space”. At this point the failures of string theory unification strongly indicate that it’s not such an interesting region. It seems likely that we’d be better off if most theorists focusing on phenomenology of this failed program were to pick something else to work on.

Update: Will Kinney has a Twitter commentary here.

Update: For another relevant recent Will Kinney Twitter storm, see here and here.

Update: Silverstein gave some lectures to the public about this at Stanford recently, video here and here, slides here. A large part of the lectures were an advertisement for string theory, with the summary at the end

Quantum gravity (string theory) plays a subtle but important role, even contributing to our understanding of empirical measurements of early universe dynamics.

Crediting string theory with “contributing to our understanding of empirical measurements of early universe dynamics” is a peculiar way of saying that string theory produces lots of cosmological models that don’t work (see a better summary by Will Kinney at the end of this presentation).

Update: Renata Kallosh is Silverstein’s colleague at Stanford (and Andrei Linde’s wife). In an interview here she makes much simpler and stronger claims about string cosmology than does Silverstein:

string theory ideas help us to build cosmological models which fit the data from observations. Moreover, we have produced relatively simple predictions from string theory and related theories which will be testable with future detectors of primordial gravity waves.

I’m not sure what specifically she is referring to, but suspect that “prediction” here means something like the “predictions” of string cosmology that Kinney describes (see above) whose failure to be observed has in no way affected string cosmologists enthusiasm for the subject.

Update: For some more context about string theory inflation models and the issue of their testability, you could consult Silverstein’s guest post at Lubos Motl’s blog from 2014, explaining how the BICEP2 observation of that era could provide evidence for “axion monodromy inflation”.

HEPAP has been meeting the past couple days, with presentations available here. Much of the discussion is about the President’s 2018 budget proposal recently submitted to Congress, which contains drastic cuts to all sorts of programs, including for support of scientific research. In particular the proposal is to cut the total NSF budget from \$7.5 billion to \$6.65 billion (-11.3%), and the DOE science budget from \$5.4 billion to \$4.47 billion (-17%).

At the DOE, for HEP physics, the cut would be from \$825 million to \$673 million (-18.5%). For topics less popular with the new administration the cuts are even larger, e.g. a 43% cut for biological and environmental research.

At the NSF (numbers with respect to FY 2016), the proposed cut for DMS (Mathematics) is 10.3%, for Physics 8.5% (-\$23.6 million) and for Astronomy 10.3%. The FY 2016 budget number for Physics was \$277 million, of which \$13.2 million went to HEP theory.

Budget cuts on this scale would be extreme and unheard of, requiring shutting down major planned experimental projects. For some sorts of spending, this sort of cut is painful but manageable, but cutting out 18.5% of the spending on an experimental apparatus under construction may likely mean you don’t have an experiment anymore.
The HEPAP presentations are from people working for DOE/NSF and under orders to plan for these cuts and not complain about them, so I think don’t reflect at all what the real implications of such cuts would be.

There’s a summary of discussion here, including a discussion of last year’s HEP theory letter. It sounds like nothing much has been done about that, and it may not get much attention given the current situation.

It’s important though to keep in mind that this budget proposal may very well already be dead on arrival at Congress. Take a look at slide 22 of this presentation that reports that of the staffers and representatives asked about (a preliminary version of) this, only 8.4% were in favor. In recent years the US budgeting process has been quite dysfunctional, with actual budget numbers only appearing at the last minute of an opaque process leading not to a budget but to a “Continuing Resolution”. I doubt anyone has any idea what is going to happen this year, with the passing of something close to this budget probably one of the least likely eventualities. Physicists and mathematicians up in arms about these proposed budget cuts need to keep in mind the context: this budget is an extremely radical proposal of an unparalleled sort, with even larger cuts aimed at groups that are far needier than scientists (for one random example, food stamps are to be cut by 25.3%). Yes, scientists should be organizing to fight this budget, but the impacts on them and their research are one of the less important reasons for doing so.

I’m setting all comments to go to moderation. If you just want to rant pro or con about the awful situation the US is now in, please do it elsewhere. If you have any actual information about the effects of this on the physics and math communities as the budget process gets underway, that would be worthwhile and interesting. Two people tweeting about this are Kyle Cranmer and Matthew Buckley.

Updates: Details of the DOE HEP budget proposal are here. It explains that about 20-25% of the research positions funded by DOE at all levels would be eliminated. There would be an “extended shutdown of the Fermilab accelerator complex”.
About 1/3 of DOE HEP theory funding would be eliminated, but it would be replaced by an equal amount of funding for quantum information science as a subfield of HEP. Looks like someone in the Trump administration is a great believer in “It From Qubit”…

Update: According to this story, if this budget passes about 700 jobs at Argonne and Fermilab would be eliminated.