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.
In recent years a hot topic in some theoretical physics circles has been the 2013 “ER=EPR” conjecture first discussed by Maldacena and Susskind here. Every so often I try and read something explaining what this is about, but all such efforts have left me unenlightened. I’m left thinking it best to wait for this to be better understood and for someone to then produce a readable exposition.
Instead of that happening, it seems that the field is moving ever forward in a post-modern direction I can’t follow. Tonight the arXiv has something new from Susskind about this, where he argues that one should go beyond “ER=EPR”, to “GR=QM”. While the 2013 paper had very few equations, this one has none at all, and is actually written in the form not of a scientific paper, but of a letter to fellow “Qubitzers”. On some sort of spectrum of precision of statements, with Bourbaki near one end, this paper is way at the other end.
Susskind starts out:
It is said that general relativity and quantum mechanics are separate subjects that don’t fit together comfortably. There is a tension, even a contradiction between them—or so one often hears. I take exception to this view. I think that exactly the opposite is true. It may be too strong to say that gravity and quantum mechanics are exactly the same thing, but those of us who are paying attention, may already sense that the two are inseparable, and that neither makes sense without the other.
I just finished writing a book about quantum mechanics, and it all seemed to me to make perfect sense without invoking gravity, but as explained above I guess I’m one of those who is not (successfully) paying attention. Another route to understanding would be to focus on the new experimental implications of the ideas. In the abstract Susskind claims that his ideas imply that we’ll observe quantum gravity using quantum computers in a lab “sometime in the next decade or so”. When that happens maybe this will all become clearer.
Update: Sabine Hossenfelder has a commentary on the paper here.
There’s a new college-level textbook out, Cosmology for the Curious, targeted at physics courses designed to explain basics of cosmology to non-physics majors. The authors are Delia Perlov and Alex Vilenkin. Back in 2006 Vilenkin published a popular book promoting the multiverse, Many Worlds in One, which I wrote about at the time, making the obvious comment that there was nothing like a testable experimental prediction to be found in the book. It seemed to me then that the physics community would never take seriously an inherently untestable theory, recognizing such a thing as pseudo-science. I thought that the only reason claims like those of Vilenkin were getting any attention was that they had some novelty. Surely after a few more years of attempts to extract a prediction of some sort led to nothing, the emptiness of this sort of idea would become clear to all and everyone would lose interest.
Eleven years later I’m as baffled by what has happened to the field of fundamental physics as I’m baffled by what has happened to democracy in the US. As all attempts to extract a testable prediction from the multiverse have failed, instead of going away, pseudo-science has become ever more dominant, with a hugely successful publicity campaign (including a lot of “Fake Physics”) overcoming scientific failure. Now this sort of thing is moving from speculative pop science to getting the status of accepted science, taught as such to undergraduates.
Many are worried about the status of science in our society, as it faces new challenges. I don’t see how the physics community is going to continue to have any credibility with the rest of society if it sits back and allows multiverse mania to enter the canon. Non-scientists taking science classes need to be taught about the importance of always asking: what would it take to show that this theory is wrong? how do I know this is science not ideology?
Any student who reads this textbook and looks for answers to these questions in it will find just two “tests” of the multiverse proposed:
- Look for evidence of bubble collisions.
- Believe this paper, and then if you find a black hole population with a certain kind of mass spectrum, that would be evidence for the multiverse.
Of course there is no evidence for bubble collisions or such a black hole population, but these are no-lose “tests”: no matter what you observe or don’t observe, the multiverse “theory” can only win, it can never lose. Is it really a good idea to teach courses telling college students that this is how science works?
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.
Commenter CIP pointed out that today’s New York Times has one of the worst examples of string theory hype I’ve seen in a while. Based on this observation of an expected QFT anomaly effect in a condensed matter system, the NYT has an article An Experiment in Zurich Brings Us Nearer to a Black Hole’s Mysteries. Not only is the headline nonsense, but the article ends with
The experiment is also a success for string theory, a branch of esoteric mathematics that physicists have used to try to tie gravity into the Standard Model, the laws of physics that describe the other forces in the universe. But string theory has been maligned because it makes predictions that cannot be tested.
Here, Dr. Landsteiner said, string theory was used to calculate the expected anomaly. “It puts string theory onto a firm basis as a tool for doing physics, real physics,” he said. “It seems incredible even to me that all this works, falls all together and can be converted into something so down to earth as an electric current.”
There’s no connection at all to string theory here. The NYT seems to have been taken in by string theorist Landsteiner and press release hype like this, not noticing that the paper had no mention of string theory in it. The hype is timed to the paper’s publication in Nature, where the editor’s summary gets it right, referring to QFT not string theory:
Johannes Gooth et al. now provide another intriguing connection to quantum field theory. They show that a condensed-matter analogue of curved space time can add an additional, gravitational component to the chiral anomaly in Weyl semimetals. The work opens the door to further experimental exploration of previously undetected quantum field effects.
Someone really should contact the NYT and get them to issue a correction. In particular, any string theorists who care about the credibility of their field should be doing this.
Update: For a couple more stories about this, IEEE Spectrum has Black Hole Power: How String Theory Idea Could Lead to New Thermal-Energy Harvesting Tech, Nature has Big Bang gravitational effect observed in lab crystal.
Update: The author of the NYT piece did make some changes in the last two paragraphs to make things less misleading.
Update: This has finally appeared in print today, in an abbreviated version, minus among other things the string theory business.
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.
Now back from vacation, more regular blogging should resume imminently. While away, lots of press stories about claims that LIGO could be used to get “evidence for string theory”. As usual, these things can be traced back to misleading statements in a paper and the associated university press release. In this case, there had already been an initial round of hype, debunked by Sabine Hossenfelder. The new round seems to have been generated by the June 28 press release. The Guardian has a version of this, but at least there the author found someone to make the obvious point, that this is irrelevant to string theory.