Some short items on a wide variety of topics:
- The Hawking/Perry/Strominger paper on a new idea about the black hole information paradox (see here for an early discussion) based on BMS supertranslation symmetries has now appeared on the arXiv. I’m no expert on the intricate arguments about this paradox, so have no idea what the implications of this paper for that really are. However, it does seem to be a very interesting approach to quantum gravity questions (although the paper mostly deals with simpler gauge theory calculations). The ideas are squarely in the mainstream of what has been the most successful way of making progress in fundamental theory: identifying new implications of symmetries that are at the center of our core theories (the standard model and GR). Such a new understanding looks like a far more promising way forward than much of what is currently popular in the subject.
- For an example of what is currently popular, the KITP is hosting a workshop this week of the the It from Qubit Simons Collaboration, on Quantum Error Correction and Tensor Networks. I gather this is supposed to somehow explain AdS/CFT, but I’ve never understood how this is supposed to come about. Evidently I’m not the only one wondering about this. John Presskill reports that, in his talk leading off a series of lectures on this, Patrick Hayden commented that
I’m unsure what we are trying to learn from these tensor network models of holography.
- Tonight PBS will be showing the film Particle Fever, which I wrote about here. It’s a great film, highly recommended, despite the larding with comical nonsense about the multiverse (if you believe the theorists in the film, the multiverse is supposed to be tested by its prediction of a mass of 140 GeV for the Higgs). The capsule summary in the New York Times TV listing this morning for the film is “Scientists recreate conditions from the big-bang theory”. While the LHC has nothing to do with the big-bang theory, maybe this summary refers to the comedy of the theorists and another well-known TV show, in which case viewers may be a bit disappointed.
- In other LHC related news, the AMVA4NewPhysics project now has a blog, latest posting explains the basics of b-tagging.
- I’ve never been able to really make sense of many of the arguments about “Bayes’s Theorem”, and the recent attempts to justify string theory using this just seemed bizarre. John Horgan has a great explanation of what is going on here, including this take on the Bayes/string theory/multiverse business:
In many cases, estimating the prior is just guesswork, allowing subjective factors to creep into your calculations. You might be guessing the probability of something that–unlike cancer—does not even exist, such as strings, multiverses, inflation or God. You might then cite dubious evidence to support your dubious belief. In this way, Bayes’ theorem can promote pseudoscience and superstition as well as reason.
Embedded in Bayes’ theorem is a moral message: If you aren’t scrupulous in seeking alternative explanations for your evidence, the evidence will just confirm what you already believe. Scientists often fail to heed this dictum, which helps explains why so many scientific claims turn out to be erroneous. Bayesians claim that their methods can help scientists overcome confirmation bias and produce more reliable results, but I have my doubts.
And as I mentioned above, some string and multiverse enthusiasts are embracing Bayesian analysis. Why? Because the enthusiasts are tired of hearing that string and multiverse theories are unfalsifiable and hence unscientific, and Bayes’ theorem allows them to present the theories in a more favorable light. In this case, Bayes’ theorem, far from counteracting confirmation bias, enables it.
- The recent Munich conference trying to justify string theory by Bayesian methods wasn’t the only example of European funding for philosophers to weigh in on the latest in fundamental physics. Another just announced European LHC-related project is a 2.5 million Euro research unit aiming to investigate the LHC “from an integrated philosophical, historical and sociological perspective.”
- I just ran across a recent paper by Kristian Camilleri and Sophie Ritson on The role of heuristic appraisal in conflicting assessments of string theory. It is very good, unlike almost every other discussion of this topic, I think it gets right the central serious argument of the “string wars”: how does one evaluate the prospects for the string unification idea? There is no simple answer to this, you need to understand what the state of efforts to connect a hoped for unified string theory to reality really are, how they have evolved, and try to make a sensible judgment about whether this is a failed idea or whether there is hope left. I highly recommend reading this for those who are not completely tired of this subject.
- In the same journal I noticed another quite good article, by Porter Williams on naturalness. He carefully explains the different incarnations of “naturalness” and I think comes to the right conclusion that it is best thought of as the idea that physical behavior at widely different distance scales should not be correlated. By the way, the name “naturalness” for this is a bit of marketing genius (how could “nature” not be “natural”?).
- In geometric representation theory news, the Simons Center is running a program on the topic this month, videos here. Here at Columbia Roman Bezrukavnikov will be the Spring 2016 Eilenberg lecturer, with his topic “Geometric categorification in representation theory”. I believe talks will be Thursdays at 2:40, watch the Columbia math department website for more news.
- Personally, I’m about to head out tomorrow night on vacation, so expect minimal blogging and possibly even shutting off of comments. When I get back, I’ll be teaching our spring semester graduate course on groups and representations, see here. Also trying to finish my book on quantum theory and representation theory. Current state (see here, comments always welcome) is that I’ve gone over and rewritten the first 34 chapters (except the introduction), planning on rewriting and adding material to the rest of the manuscript this semester. This better be done by this summer, partly because that’s when it is supposed to be delivered to Springer, partly because I’m already quite tired of this project and want to work on other things…
Update: Any mention of Bayesianism seems to attract a large number of people who want to discuss it, especially aspects that have nothing to do with the string theory/multiverse business. Please discuss this topic with John Horgan at his blog.
Update: Sabine Hossenfelder has more on the Hawking/Perry/Strominger paper here.
Update: Scientific American has an interesting interview with Strominger, who explains some of the ideas behind Hawking/Perry/Strominger. Jacques Distler has come out of retirement at Musings to object that this work violates two central ideological tenets: one should not pay attention to gauge invariance, and the answer to all questions should be string theory or AdS/CFT.