## Theorists Without a Theory

I had been intending to write something here on the blog about this essay by George Ellis, so when I was contacted by someone at Inference about writing a letter in response, I did so for publication there. It has now appeared in their latest issue, with the title Theorists Without a Theory.

The topic is one I’ve addressed here all too often, but the main point I was trying to make is perhaps a new one. When I was writing here about the controversy over inflation one thing that struck me was that the pro-inflation side was responding to arguments that their theory didn’t solve the problem it was supposed to by in effect saying “the real theory is much more complicated” (see the paragraph beginning “Besides our disagreement…” on page 3 here). One way of seeing part of what is going on here is that most of what gets advertised as “theories” of inflation are actually more appropriately described as toy models. They involve a single inflaton field with a simple potential and unknown couplings to matter, intended as a toy model for the real theory (which will have lots of fields, complicated potentials and specified couplings to matter). An aspect of the controversy is one side pointing out that this theory doesn’t solve problems it is supposed to solve, with the other side arguing that it’s just a toy model.

People sometimes note that there’s a terminological problem with “string theory”, in that the public is often told that “theories” are solidly tested parts of science, which is not true in this case. The actual usage among physicists is different though, with “theory” often used to mean a specific mathematical model or set of models, with no implicit claim of a successful experimental test. A lot of the problem with the usage “string theory” is that no one knows what the actual theory is: it’s a conjecture that a theory with certain specific limits exists. The main point I was trying to make in this piece is that to a large degree the arguments over the scientific status of string theory (and of its supposed landscape and multiverse) revolving around its lack of testability are moot, since the underlying problem is something different: that there is no real theory to argue about. String theorists often try and evade this problem by a terminological shift: string theory is not a “theory”, it’s a “framework”. “Framework” is a much more ill-defined term than the already ill-defined “theory”. A theorist who says “I have a framework, not a theory” is actually saying that they are just a theorist without a theory.

Note: there are a couple minor problems with the copy-edited version of my text. Perhaps these will get fixed, but until they do, in the first paragraph read “it is not new and subtle issues about the relation of theory and experiment that are relevant” for “it is not new that subtle issues about the relation of theory and experiment are relevant”. In the fourth, read “space parametrizing” for “space-parametrizing”.

Posted in Multiverse Mania | 1 Comment

## Various Physics News

First, two local events, involving well-known physics bloggers:

• Last Thursday I had the pleasure of attending an event at NYU featuring Sabine Hossenfelder and Natalie Wolchover in conversation. You can watch this for yourself here. If you’re not following Hossenfelder on her blog and at Twitter (and planning to read her forthcoming book), as well as reading Wolchover’s reporting at Quanta magazine, you should be.
• Next week there will be an event out in Brooklyn advertised as covering the Scientific Controversy over string theory. The idea seems to be to address this controversy by bringing to the public two well-known and very vocal proponents of one side of it.

For a Q and A with another well-known physics blogger, there’s Tommaso Dorigo at Physics Today.

For a couple of encouraging indications that the theoretical physics community may finally be taking seriously the need to give up on failed thinking and try something new, there’s

• A conference next month in Italy on Weird Theoretical Ideas (Thinking outside the box).
• An interesting talk at a recent IPMU conference by Yuji Tachikawa. I like his conclusion:

Basically, all the textbooks on quantum field theories out there use an old framework that is simply too narrow, in that it assumes the existence of a Lagrangian.

This is a serious issue, because when you try to come up e.g. with a theory beyond the Standard Model, people habitually start by writing a Lagrangian … but that might be putting too strong an assumption.

We need to do something

In General Relativity related news, there’s a new edition out of Misner, Thorne and Wheeler, the book from which many of us learned both geometry and GR. It comes with new prefaces from David Kaiser as well as Misner and Thorne (which an appropriate search on the Amazon preview might show you…). In other Wheeler-related news, Paul Halpern has a new book out, The Quantum Labyrinth, which tells the entangled stories of Feynman and Wheeler.

Finally, also GR related, the Perimeter Institute has announced the formation of a new cosmology-focused “Centre for the Universe”, funded by an anonymous 10-year $25 million donation. It will be led by cosmologist Neil Turok, who is soon to step down as director of Perimeter. Posted in Uncategorized | 23 Comments ## Breakthrough Prize 2018 The Breakthrough Prizes for 2018 will be awarded at a ceremony on December 3, I believe at the usual NASA Hangar 1 in Mountain View. The next day Stanford will host the 2018 Breakthrough Prize symposium, which one will be able to watch live from the Breakthrough Prize Facebook page. The symposium schedule is available here, and while it does not list the Prize awardees, it does appear to list the titles of the talks. From this it looks like the math \$3 million will go to a geometer, who will talk about “Geometry at Higher Dimensions”. There may be several \$100,000 New Horizons Prizes for younger mathematicians, but at least one will be to an analytic number theorist, who will talk about “Analytic Number Theory in Everyday Life”. For the \$3 million physics prize, it looks like it is going to be split five ways and go to cosmologists/astrophysicists. The talks by laureates are “The Next Decade in Cosmology”, “Gravitational Waves and Cosmology”, “Search for Extraterrestrial Intelligence”, “A New Instrument for Listening to the Universe” and “The Beginning and End of the Universe”.

Posted in Uncategorized | 11 Comments

## Various Stuff

A few links that may be of interest. Mathematics first:

• A seminar “Lectures Grothendieckiennes” on the mathematical ideas of Alexander Grothendieck is taking place this year in Paris, and has just recently started up.
• My ex-Columbia colleague Jeff Achter is one of the authors of an unusual new math paper: Hasse-Witt and Cartier-Manin matrices: A warning and a request. The paper points out that papers of Manin at some points confused an operator and its dual, leading to potential sign errors in later papers that reference Manin’s results. I’m quite sympathetic to the problem, having at various points fallen victim to similar confusions while writing my book (I hope they have all been resolved in the final version, wouldn’t bet anything really valuable on it…).
• Nature has an excellent obituary of Vladimir Voevodsky, written by Dan Grayson.

On the physics side:

• The LHC has now ended data-taking at 13 TeV for the year (a recent summary is here) and will start up again next spring. The machine ended up delivering about 50 inverse fb each to CMS/ATLAS (bettering the goal of 45), of which about 45 was recorded. Results published so far typically use 36 inverse fb from previous year’s data, so next year we should start seeing results based on a total 13 TeV data set of up to 80 inverse fb.
• Still no WIMPs. Frank Wilczek surveys searches for his favorite dark matter alternative here.
• At Big Think, Eric Weinstein has a take on what’s gone wrong with theoretical physics over the past 40 years that I’m mostly in agreement with.
Posted in Uncategorized | 11 Comments

## Where the Money Comes From

Since returning from a vacation partly spent isolated from the internet, I’ve been catching up and noticed that some of the most prominent sources of funding for math and physics research have been making the news:

• The New York Times and other sources have extensive reports based on leaked records from an offshore law firm that specializes in helping you avoid inconvenient US tax and reporting requirements. The story starts out with the example of Jim Simons, who has become the largest non-governmental funder of math and physics research. His Simons Foundation has been doing an excellent job of providing such funding. They have about \$3 billion in assets, annual income of around \$500 million. The Times reports that Simons (with a net worth of about \$18.5 billion) has an offshore version of the Foundation, the Simons Foundation International, with assets of \$8 billion, dwarfing the onshore version.
• The assets of these Foundations are presumably largely invested in the secretive and extremely successful Renaissance Technologies hedge fund, which also is the employer of quite a few physicists and mathematicians. I’ve asked many people over the years, but have never found anyone who knows (or will admit to knowing) what it is that RenTech does that is so successful. A peculiar aspect of the coming age of private math/physics research funding is that no one getting this funding really knows where the money comes from.

In other news while I was away the CEO of RenTech, Robert Mercer, was finally induced to leave. Mercer had drawn a lot of attention recently since he in recent years has been taking the opposite tack to Simons, funding institutions devoted to promoting untruth over truth (e.g. Breitbart News), achieving fantastic success last year. He also has branched out from doing whatever secretive things RenTech does to make mountains of money using computers and data, starting up a firm called Cambridge Analytica, a firm involved in secretively using computers and data to undermine democracy in the US and elsewhere. I had been wondering for quite a while what Simons thought of Mercer’s activities. My understanding of highly-paid finance jobs was that your employer pays you a lot of money in return for having your full attention and devotion to not having negative stories about them come to public attention, so Mercer’s continued employment was surprising. It seems that Simons finally had enough, after realizing how much damage Mercer was doing to his firm, in particular by creating a situation that would discourage many people from wanting to work there (there also was a campaign underway to get institutions to divest from investments with RenTech).

• Another high profile source of funding for math and physics, in this case for cash prizes to mathematicians and physicists, has been venture capitalist Yuri Milner, with his Breakthrough Prize organization. New prizes will be announced in three weeks at a December 3 prize ceremony (I also believe there will be an associated Breakthrough Prize symposium held at Stanford shortly thereafter). It has always been well-known that much of Milner’s wealth derived from investments in Facebook and Twitter. Less well-known and recently revealed was that a major source of the funds for these investments was Russian state organizations closely tied to Vladimir Putin.
• Turning to sources of public funding, there’s not very positive news about a possible ILC collider in Japan, with reports of a cutback of the proposal from a 500 GeV to a 250 GeV machine (which would still cost about $7 billion). • Foreign policy magazine has an article discussing the proposal for a huge new collider in China (discussed here). The point of view of the article is quite critical of the idea of locating a huge new project in a country with an increasingly authoritarian regime: China’s next-generation supercollider will unlock secrets of the universe — and destroy the ideals of the scientists running it. Luckily, for another more local prominent large country with an increasingly authoritarian and xenophobic regime, the issue of a possible problem with locating an international collider project there isn’t likely to come up since its leaders have no interest in funding such projects. Posted in Uncategorized | 15 Comments ## Quantum Theory, Groups and Representations While I was away last week on vacation, it seems that Springer has published my book on quantum mechanics and representation theory (previously discussed in various blog posts). The Springer page is here, your institution may provide access to the content (and a$24.99 MyCopy softcover) at the Springer Link page for the book. I’ve retained copyright for the content of the book and a version with essentially the same content as the Springer version is available from my website here. The Springer version has their formatting, copy-editing and metadata. The Amazon webpage for the book (if you’re in the mood to write a review there, feel free) is here.

I haven’t yet seen a physical copy of the book, don’t know how long it will take for them to start printing copies. From people at Springer I learned last year that they no longer print and store copies of such books, they’re now always printed on demand (with the quality of the printing dependent on where you order your book from, German printers are quite good I hear..).

Just before leaving on vacation, I gave an introductory talk on some of the themes of the book at LaGuardia Community College (slides here). This week I’ll be giving a similar talk at a math department colloquium at Queensborough Community College this Wednesday (1 pm, Science building, S-213).

Posted in Quantum Theory: The Book | 10 Comments

## This Week’s Hype

Yet another entry in the long line of nonsensical hype about fundamental physics driven by misleading university press releases is today’s news that CERN Scientists Conclude that the Universe Should Not Exist. Tracking this back through various press stories (see here, here and here), one finds that the original source, as always, is a university press release designed to mislead journalists. In this case it’s Riddle of matter remains unsolved from Johannes Gutenberg University Mainz, a press release designed to promote this paper in Nature.

The paper reports a nice experimental result, a measurement of the antiproton magnetic moment showing no measurable difference with the proton magnetic moment. This is a test of CPT invariance, which everyone expects to be a fundamental property of any quantum field theory. The hype in the press release confuses CPT invariance with CP invariance. We know that physics is not CP invariant, with an open problem that of whether the currently known sources of CP non-invariance are large enough to produce in cosmological models the observed excess of baryons over antibaryons. An accurate version of the press release would be: “experiment finds expected CPT invariance, says nothing about the CP problem.”

If this experiment had found CPT non-invariance, the implications for early universe baryon-antibaryon asymmetry would have been of minor interest compared to the revolutionary discovery that a fundamental theorem of quantum field theory was violated, shattering our understanding of fundamental physics in terms of quantum field theory.

Posted in This Week's Hype | 24 Comments

## Short Items

A few short items:

• My graduate school roommate Nathan Myhrvold has a new book coming out this month, a five-volume series about the science of bread, based on several years of research into the subject at his laboratory near Seattle. Robert Crease has gone out to visit, and gives a wonderful detailed report on The physics of bread in this month’s Physics World.
• An article at FQXI on multiverse research they are funding seemed to finally give me an understanding of what this is all about:

These are the two conceptually hardest questions in cosmology, according to Raphael Bousso, a theoretical physicist at the University of California, Berkeley. They go to the core of what it means to exist as a human being making sense of the universe we find ourselves in. And, he adds, unfortunately, there is very little physical knowledge to go on when it comes to working out the answer.

Undaunted by the lack of tools to help them, theatrical physicists Eugene Lim of King’s College London, UK, and Richard Easther of the University of Auckland, New Zealand, are…

This all of a sudden made things clear: what is going on is “theatrical physics”, not “theoretical physics”. Going on like this about the multiverse is performance art.

Unfortunately I just noticed that this page has been edited (new version here), removing the enlightening characterization of what this is about.

• I’m glad to see that Natalie Wolchover has just won an AIP award for her writing about physics, in particular for a piece on how physicists are dealing with the “nightmare scenario”. While she’s perhaps the best professional journalist writing about these topics, for coverage of this from a professional physicist, the best you can find is Sabine Hossenfelder’s blogging at Backreaction. I’m pleased to hear that the two of them will be appearing at an event here next month in NYC, talking about Making Sense of Mind-Blowing Physics at NYU on Nov. 16.

Update: Sabine Hossenfelder has a book coming out next year, which should be fascinating (although I suspect I’ll have something to disagree with…).

Gian Francesco Giudice has a long essay about the status of particle physics, post-negative LHC results. For better and worse, I think it captures well the view of many mainstream theorists.

Posted in Uncategorized | 8 Comments

## Shut Up and Calculate!?

I noticed recently that Nima Arkani-Hamed was giving a talk at Cornell, with the title Three Cheers For “Shut Up And Calculate!” In Fundamental Physics. No idea whether or not video is now or will become available.

From the abstract one can more or less guess what sort of argument he likely was making, and it’s one I’m mostly in agreement with. “Shut Up and Calculate!” is pretty much my unspoken reaction to almost everything I read purporting to be about foundational issues in quantum mechanics. I have in mind in particular discussions of the measurement problem, which often consist of endless natural language text where one struggles to figure out exactly what the author is claiming. An actual calculation showing what happens in a precise mathematical model of a “measurement” would be extremely helpful and likely make much clearer exactly what the problem is (or, sometimes, whether or not there even is a problem…). Such calculations are all too few in a huge literature.

Over the last few years, while teaching and writing a book about the mathematics of quantum mechanics, the tedious exercise of trying to get all signs right in calculations has sometimes turned out to be quite illuminating, with tracking down a mysterious inconsistency of minus sign leading me to realize that I wasn’t thinking correctly about what I was doing. I’m all too aware that this kind of calculational effort is something I too often avoid through laziness, in favor trying to see my way through a problem in some way that avoids calculation.

On the other hand, I’m not quite ready to sign up for “Three Cheers”, might just stick to “Two Cheers”. For a perfect example of what’s wrong with the “Shut Up and Calculate!” philosophy, one can take a look at the forthcoming Workshop on Data Science and String Theory planned for Northeastern in a month or so. They have a Goals and Vision statement which tells us that they plan to:

treat the landscape as what it clearly is: a big data problem. In fact, the data that arise in string theory may be some of the largest in science.

About being the “largest”, I think they’re right. The traditional number of 10500 string theory vacua has now been replaced by 10272,000 (and I think this is per geometry. With 10755 geometries the number should be 10272,755). It’s also the case that “big data” is now about the trendiest topic around, and surely there are lots of new calculational techniques available.

The problem with all this is pretty obvious: what if your “data set” is huge but meaningless, with nothing in it of any significance for the problem you are interested in (explaining the Standard Model)? This is not a new project, it’s an outgrowth of the String Vacuum Project, which I wrote about here, here and here. This started with a 2005 funding proposal, ended up getting funded by the NSF during 2010-2014. From the beginning there were obvious reasons this sort of calculational activity couldn’t lead to anything interesting, and as far as I can tell, nothing of any value came out of it.

For an opposite take to mine on all this, see the paper Big Numbers in String Theory, by Bert Schellekens. It contains an odd June 2017 preface explaining that it was supposed to be part of special issue of Advances in High Energy Physics devoted to “Big Data” in particle and string phenomenology (“all the ways we use high performance computing in addressing issues in high energy physics, and (in particular) the construction of databases of string vacua”). This issue was cancelled “as requested by the Guest Editors”. I wonder what the reason for this cancellation was, in particular whether it had anything to do with part of the topic of the special issue being considered by some to be obvious nonsense.

Posted in Multiverse Mania | 61 Comments

## 50 Years of Electroweak Unification

The 50th anniversary of electroweak unification is coming up in a couple days, since Weinberg’s A Model of Leptons paper was submitted to PRL on October 17, 1967. For many years this was the most heavily cited HEP paper of all time, although once HEP theory entered its “All AdS/CFT, all the time” phase, at some point it was eclipsed by the 1997 Maldacena paper (as of today it’s 13118 Maldacena vs. 10875 Weinberg). Another notable fact about the 1967 paper is that it was completely ignored when published, only cited twice from 1967 to 1971.

The latest CERN Courier has (from Frank Close) a detailed history of the paper and how it came about. It also contains a long interview with Weinberg. It’s interesting to compare his comments about the current state of HEP with the ones from 2011 (see here), where he predicted that “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.”

Today he puts some hope in a non-renormalizable Majorana mass term for neutrinos as evidence for new physics. As for the future:

As to what is the true high-energy theory of elementary particles, Weinberg says string theory is still the best hope we have. “I am glad people are working on string theory and trying to explore it, although I notice that the smart guys such as Witten seem to have turned their attention to solid-state physics lately. Maybe that’s a sign that they are giving up, but I hope not.”

On this last sentiment, I have the opposite hope. He also shares what I think is a common hope for what will save the field (a smart graduate student with a new idea):

Weinberg also still holds hope that one day a paper posted in the arXiv preprint server by some previously unknown graduate student will turn the SM on its head – a 21st century model of particles “that incorporates dark matter and dark energy and has all the hallmarks of being a correct theory, using ideas no one had thought of before”.

Perhaps current training of graduate students in theory should be rethought, to optimize for this.

Update: A colloquium talk by Weinberg on this topic will be live-streamed here on October 17.

Posted in Uncategorized | 16 Comments