Not Even Wrong

If you’re a fan of The Big Bang Theory, perhaps you’ve seen the latest episode, The Retraction Reaction. If not, you might be interested in the following transcript (taken from here). The show has always done a good job of getting the science right, for an interview with their physics consultant David Saltzberg, see here.

The episode begins with a Science Friday interview of physicist Leonard Hofstadter by Ira Flatow:

FLATOW: So, it has been five years since the discovery of the Higgs boson– what’s the next big thing gonna be?

LEONARD: Wow, that’s hard to say. There’s so much going on. We’ve been collecting tons of data that could revolutionize the way we understand the universe. For instance, there’s a particle called a squark, which could prove supersymmetry.

FLATOW: That is interesting. Have you found it?

LEONARD: What, the squark?

FLATOW: Yes.

LEONARD: No, no. Wouldn’t that be exciting? But we’re also looking for the selectron, the gluino and the neutralino.

FLATOW: Well, and have you found that?

LEONARD: No. Another fun sidenote– I went to high school with a girl named Theresa Gluino, but it didn’t cost $2 billion to find her. She was smoking behind the gym. (laughs)

FLATOW: So, what have you found?

LEONARD: Uh, nothing, actually. We’ve got the best equipment and the best minds all working on it. Although, some days I’m, like, ugh we’ve spent so much money. Why haven’t we found anything? What are we doing?

After a segment in which neuroscientist Amy explains that she doesn’t tell physicist boyfriend Sheldon about her new lab equipment since

AMY: We’ve been getting so much more funding than physics, he’s been a little sensitive.

another scene features Leonard called into the office of a university administrator:

LEONARD: I have to say I’m a little nervous.

Ms. DAVIS: You should be.

LEONARD: Look, I know I screwed up, but it was only one interview.
How much damage could it have caused?

Ms. DAVIS: Would you like for me to read you the e-mails from donors asking why are they giving us money if physics is a dead end?

LEONARD: I didn’t say it was a dead end. I just said that I was worried it might be.

Ms. DAVIS: So if I just said I was worried you might not have a job next week, how would you feel?

LEONARD: Light-headed, and glad you asked me to sit down. Okay, just tell me what I can do.

Ms. DAVIS: I’m gonna need you to make a statement saying that you misspoke, and that you’re confident the physics community is close to a major breakthrough.

LEONARD: You want me to lie.

Ms. DAVIS: Look, Dr. Hofstadter, I’m counting on you. I think that you are the smartest physicist at this university.

LEONARD: Really?

Ms. DAVIS: See? Lies. They’re not that hard.

Leonard then has this exchange with Penny:

PENNY: Hey, come on, look, you said a few dumb things on the radio– what is the worst that could happen?

LEONARD: I may get fired.

PENNY: Okay, well, even if you did, you could find another job.

LEONARD: Yeah, who wouldn’t want to hire the physicist who publicly said physics is dead? Well, I wouldn’t put that under “special skills”. I can fix it, I just need to write a retraction I don’t believe in– basically sell out to keep my job.

PENNY: Great, I’ll leave you to it.

He then goes to talk to string theorist Sheldon Cooper:

LEONARD: Sheldon, it’s me.

SHELDON: What?

LEONARD: Look, I know you’re mad, but I have to write a statement that says the physics community is close to a breakthrough, and since you actually believe that, I could really use your help.

SHELDON: Sorry, I can’t.

LEONARD: Come on, don’t be like that.

SHELDON: What? Look. (sighs) Not all science pans out. You know, we’ve been hoping supersymmetry was true for decades, and finally, we built the Large Hadron Collider, which is supposed to prove it by finding these new particles, and it-it hasn’t. And maybe supersymmetry, our last big idea, is simply wrong.

LEONARD: Well, that sounds awful. Now I get why everyone hates me.

Penny later comes in:

PENNY: So you guys are upset because the collider thing disproved your theories?

LEONARD: It’s worse than that. It hasn’t found anything in years, so we don’t know if we’re right, we don’t know if we’re wrong. We don’t know where to go next…

PENNY: Come on. You guys are physicists. Okay? You’re always gonna be physicists. And sure, sometimes, the physics is hard, but isn’t that what makes it boring?

The episode ends with a visit to the grave of Richard Feynman, and a reference to Feynman’s story about how he got himself out of a slump in his work when he was at Cornell:

WOLOWITZ: He did so much. And here we are, stuck and letting him down. You know, Feynman used to say he didn’t do physics for the glory or the awards, but just for the fun of it. He was right. Physics is only dead when we stop being excited about it.

All in all, a pretty accurate portrayal of the situation in high energy physics theory, with a reasonable take on what to do about it.

Update: A correspondent points me to a rather Leonard Hofstadter-ish interview with Steven Weinberg back in 2011, where he says:

It may be that they’ll only discover the Higgs boson and nothing else, and we’ll be left looking at our toes and wondering what we’re going to do next. There may be nothing really new that can be reached with the LHC,

I have fears… If all they discover is a Higgs boson with roughly the properties that the theory predicts and nothing else, I don’t know where the field is going to go.

When asked a rather Ira Flatow-ish question: “Wouldn’t you say to a young person that now would be a very exciting time to go into physics?” his answer is

Whether or not it would be a good career move depends on what they are going to discover.

If all they discover is the Higgs boson and it has the properties we expect, then No, I would say that the theorists are going to be very glum.

At this point, Kip Thorne and Rainer Weiss of LIGO have (deservedly) won just about every scientific prize out there, for the first observation of gravitational waves. I don’t know of anyone who doesn’t believe they’ll be getting the Physics Nobel tomorrow morning. With an open spot in the usual limitation to three (Ronald Drever passed away earlier this year), perhaps Barry Barish will also get the nod. Most appropriate would be to use the third slot to give an award to the entire LIGO collaboration, but it seems likely that the tradition of not honoring collaborations will continue. There will be a live webcast of the announcement at 5:45am EST available here.

Update: Congratulations to the winners. I think Natalie Wolchover speaks for all science journalists when she writes:

Thrilled they won, thrilled not to spend this morning speed-reading about some bizarre condensed matter phenomenon.

Update: A couple things I’ve learned from comments and other coverage of this:

• Some physicists have no sense of humor and are either unaware of or ungrateful for the excellent job Natalie Wolchover and others at Quanta magazine have been doing in writing high-quality stories about a wider range of topics in physics than anyone else (see here and here, related here).
• All evidence is that on October 16th we’ll get announcement of observation of gravitational waves with an optical counterpart, with details at this conference in Baton Rouge.

• I don’t know if I ever mentioned this, but quite a while ago I replaced the “latexrender” TeX plugin being used here by a mathjax one. As I find time, I’m now going back and editing old posts to get rid of latexrender tags and make the equations more mathjax friendly. As far as comments are concerned, you can add TeX content by using standard math delimiters \$, or \$\$ for displayed math. If you want to comment about US dollars, put a backslash before your dollar signs to avoid the interpretation as TeX.

  One reason I hadn’t advertised this much is that I know it’s hard to get TeX right the first time, so people’s comments with TeX would be likely to often not work properly. I’ve added a plugin that lets you edit your comment for 5 minutes after you write it. This should be useful for typos, as well as for fixing TeX problems (note that you need to refresh the page to get the math to display).

• For a philosopher’s take on evaluating string theory, see this talk by James Ladyman, on Cosmic Dreams. Material on string theory is near the end, and just makes the obvious point that having no experimental evidence for the theory is a huge problem, no matter what efforts are made to change the usual way scientific theories are evaluated.
• A hot topic these days in the math community is the conjecture that local Langlands can be understood as geometric Langlands for the Fargues-Fontaine curve. My attempts to learn about this so far haven’t had a lot of success, but I now have new-found hope. At Harvard there’s a seminar going on this semester on the topic, and it has a website which so far features explanations of some of the mathematics involved from Jacob Lurie and Dennis Gaitsgory. In London, the London Number Theory Seminar also has a study group devoted to this topic (website here, although seems to have disappeared for the moment).
• LQP2 (Local Quantum Physics Crossroads, v.2.0) is a website that gathers various information about relativistic quantum theory.
• In November Perimeter will host what should be an interesting workshop on the question of how to make sense of the Path Integral for Gravity.
• A memorial for Maryam Mirzakhani will take place at Stanford on October 21, with a live feed available here.
• As always, Quanta magazine keeps publishing a wide range of very high quality articles about math and physics, covering different topics than everyone else. Most recently, on the math side, see an article by Erica Klarreich on Pariah Moonshine and on the physics side, Robert Henderson on possible searches for long-lived particles possibly from a “hidden sector”..

Update: Commenter sdf points out this historical article by Pierre Colmez about the Fargues-Fontaine curve, preprint of a preface to an Asterisque volume.

Earlier this week Zohar Komargodski (who is now at the Simons Center) visited Columbia, and gave a wonderful talk on recent work he has been involved in that provides some new insight into a very old question about QCD. Simplifying the problem by ignoring fermions, QCD is a pure SU(3) Yang-Mills gauge theory, a simple to define QFT which has been highly resistant to decades of effort to better understand it.

One aspect of the theory is that it can be studied as a function of an angular parameter, the so-called $\theta$-angle. Most information about the theory comes from simplifying by taking $\theta=0$, which seems to be the physically relevant value, one at which the theory is time reversal invariant. There is however another value for which the theory is time reversal invariant, $\theta=\pi$, and what happens there has always been rather mysterious.

The new ideas about this question that Komargodski talked about are in the paper Theta, Time Reversal and Temperature from earlier this year, joint work with Gaiotto, Kapustin and Seiberg. Much of the talk was taken up with going over the details of the toy model described in Appendix D of this paper. This is an extremely simple quantum mechanical model, that of a particle moving on a circle, where you add to the Lagrangian a term proportional to the velocity, which is where the angle $\theta$ appears. You can also think of this as a coupling to an electromagnetic field describing flux through the circle.

Even if you’re put off by the difficulty of questions about quantum field theories such as QCD, I strongly recommend reading their Appendix. It’s a simple and straightforward quantum mechanics story, with the new feature of a beautiful interpretation of the model in terms of a projective representation of the group O(2), or equivalently, a representation of Pin(2), a central extension of O(2). In the analogy to SU(N) Yang-Mills, it is the $\mathbf Z_N$ symmetry of the theory that gets realized projectively.

Komargodski himself commented at the beginning of the talk on the reasons that people are returning to look again at old, difficult problems about QCD. The new ideas he described are closely related to ones that are part of the recent hot topic of symmetry protected phases in condensed matter theory. It’s great to see that this QFT research may not just have condensed matter applications, but seems to be leading to a renewal of interest in long-standing problems about QCD itself.

Besides the paper mentioned above, there are now quite a few others. One notable one is very recent work of Komargodski and collaborators, Time-Reversal Breaking in QCD4, Walls and Dualities in 2+1 Dimensions.

Quanta magazine today has a column by Robbert Dijkgraaf that comes with the abstract:

Reductionism breaks the world into elementary building blocks. Emergence finds the simple laws that arise out of complexity. These two complementary ways of viewing the universe come together in modern theories of quantum gravity.

It struck me that at this point I don’t know what a “modern theory of quantum gravity” is. Much of the article is a clear explanation of the usual story of the renormalization group and effective field theory, but towards the end, when quantum gravity comes up, I have trouble following. String theory has gone from being an exciting new idea to being part of historical tradition:

Traditional approaches to quantum gravity, such as perturbative string theory, try to find a fully consistent microscopic description of all particles and forces. Such a “final theory” necessarily includes a theory of gravitons, the elementary particles of the gravitational field.

That “reductionist” tradition is opposed to a new “emergent” holographic theory, and we’re told that

The present point of view thinks of space-time not as a starting point, but as an end point, as a natural structure that emerges out of the complexity of quantum information, much like the thermodynamics that rules our glass of water. Perhaps, in retrospect, it was not an accident that the two physical laws that Einstein liked best, thermodynamics and general relativity, have a common origin as emergent phenomena.

In some ways, this surprising marriage of emergence and reductionism allows one to enjoy the best of both worlds. For physicists, beauty is found at both ends of the spectrum.

Dijkgraaf seems to be saying that a viable emergent theory of four-dimensional quantum gravity based on the complexity of quantum information has been found, but I seem to have missed this. Can someone point me to a paper describing it?

This semester I’m teaching the first semester of Modern Geometry, our year-long course on differential geometry aimed at our first-year Ph.D. students. A syllabus and some other information about the course is available here.

In the spring semester Simon Brendle will be covering Riemannian geometry, so this gives me an excuse to spend a lot of time on aspects of differential geometry that don’t use a metric. In particular, I’ll cover in detail the general theory of connections and curvature, rather than starting with the Levi-Civita connection that shows up in Riemannian geometry. I’ll be starting with connections on principal bundles, only later getting to connections on vector bundles. Most books do this in the other order, although Kobayashi and Nomizu does principal bundles first. In some sense a lot of what I’ll be doing is just explicating Kobayashi and Nomizu, which is a great book, but not especially user-friendly.

A major goal of the course is to get to the point of writing down the main geometrically-motivated equations of fundamental physics and a few of their solutions as examples. This includes the Einstein eqs. of general relativity, although I’ll mostly be leaving that topic to the second semester course.

Ideally I think every theoretical physicist should know enough about geometry to appreciate the geometrical basis of gauge theories and general relativity. In addition, any geometer should know about how geometry gets used in these two areas of physics. I’ve off and on thought about writing an outline of the subject aimed at these two audiences, and thought about writing something this semester. Thinking more about it though, at this point I’m pretty sick of expository writing (proofs of my QM book are supposed to arrive any moment…). In addition, I just took a look again at the 1980 review article by Eguchi, Gilkey and Hanson (see here or here) from which I first learned a lot of this material. It really is very good, and anything I’d write would spend a lot of time just reproducing that material.

Update: Steve Bryson sent me another excellent suggestion for a book covering these topics, aimed at the physical applications: David Bleecker’s Gauge Theory and Variational Principles.

• The Stacks Project (see an earlier post here) had a very successful workshop in Ann Arbor earlier this month. This is a remarkable effort pioneered by Johan de Jong to produce a high quality open source reference for the field of algebraic geometry. It now is over 6000 pages, with an increasingly large number of papers citing it (according to data from Pieter Belmans, 85 citations in the arXiv so far in 2017 alone). During the workshop plans were discussed for the future of the project, with work on a new version of the project infrastructure underway (see slides and a blog post from Belmans).
• The latest AMS Notices has a wonderful article by my Barnard/Columbia colleague Dusa McDuff about her remarkable family history and reflecting on her equally remarkable mathematical career. A post earlier this year discussed a Quanta article about her recent work with Katrin Wehrheim on technical issues in the foundations of symplectic topology. Kenji Fukaya has recently written something for the Simons Center website (see here) explaining his take on this story.
• The Stanford Encyclopedia of Philosophy has a new entry about the fine-tuning problem, by Simon Friedrich.
• The LHC operators have run into some difficulty in recent weeks (reflected in the accumulated luminosity plots here and here), with problems centered around an unknown source of gas in the beam pipe at a specific location, leading to losses of the beam. Some information about this is available here. The past few days they seem to be having success running the machine with around 1500 bunches, much less than the 2500 or so of earlier in the summer. The target for the year is 40 inverse fb which may still be achieved, while more optimistic numbers that looked plausible earlier now seem less likely.

Update: Joe Polchinski has put on the arXiv a long autobiographical document, with a detailed discussion of his scientific career.

Update: As mentioned in the comments, Go Yamashita has posted a long document surveying Mochizuki’s claimed proof of the abc conjecture. Experts may find that this makes it more possible to understand and check the claimed proof, we’ll see.

Update: Also at the Simons Center website, there’s an interview with Michael Green. It’s interesting to see that in recent years his research interests have led him to getting closer to mathematics and to an appreciation of what mathematicians do. As for his claim about string theory that

I don’t think there is a substantial antagonism to it among those who have studied it, other than a few individuals who enjoy publicizing their views.

I think he’s quite wrong if you properly take “it” to refer to the aspect of string theory there is widespread antagonism to among physicists, the overhyped claims about a unified theory based on string theory.

Blogging will be light to non-existent for the next ten days or so, as I head out west on a road trip to see next Monday’s solar eclipse. Current plan is to fly to Denver tomorrow, pick up a vehicle, and head up to Wyoming the next day. If weather projections look good for the Wyoming/Idaho part of the track, that’s where we’ll plan to end up, likely camping out somewhere (accommodations along the track have long been booked up).

This will be the ninth eclipse I’ve traveled to see, and I urge anyone thinking of making a trip to the eclipse track to do so. A total solar eclipse is something quite different than a partial one, and this is a very rare opportunity to see this in the US. Besides the eclipse, a major motivation for these trips has always been that of getting to visit a more or less random place on Earth that one wouldn’t otherwise have any excuse to see. I’ve driven quickly through Idaho and Wyoming a few times over the years, look forward to spending more time in that part of the country this coming week (unless the weather there looks bad, in which case maybe we’ll end up in Oregon or Nebraska).

Some other random advice about eclipses:

• Be very careful about use of binoculars or telescopes, improper use of these at any time other than the period of totality is what can cause serious eye damage (by itself the eye is pretty good about automatically protecting itself).
• Don’t put a lot of effort into photography during totality, since that’s likely to lead to you spending the time you should be enjoying the experience fiddling with camera equipment (and not getting a good result anyway…). A simple thing to do is to set up a camera to take video of the overall eclipse scene as it happens, turn it on at some point then ignore it.

If you miss this one, next couple are far south in South America, there will be another chance in the US relatively soon, April 2024.

Update: Now back in New York. Had a very good view of the eclipse from a spectacular location: Stanley, Idaho, up in the Sawtooth mountains. Only not quite optimal part of the plan was camping out not not well-equipped for the the unexpected fact that it gets down to about freezing at night in that part of Idaho, even in August…