Why Trust a Theory?

Posted on April 5, 2019 by woit

I noticed today that Cambridge University Press has recently published Why Trust a Theory?, a volume of articles based on a December 2015 conference held in Munich. The book is available online here (if your university is paying for it…), and preprint versions of many of the contributions are on the arXiv.

The conference had its origins in a piece published a year earlier in Nature by George Ellis and Joe Silk, entitled Scientific method: Defend the integrity of physics. Ellis and Silk made a forceful case that widely advertised but inherently untestable string theory and multiverse research does damage to the public understanding of science and is a threat to the credibility of science at a time it is under attack. The piece suggested:

A conference should be convened next year to take the first steps. People from both sides of the testability debate must be involved.

Looking through the proceedings volume, there’s lots of abstract discussion of philosophy of science and some diversity of points of view on the multiverse. When it comes to string theory though, the organizers interpreted “people on both sides” to mean bringing in one person willing to point out that there is a problem with string theory, and an army of string theorists to defend the theory. On the issue of the problems of string theory, the volume contains nearly 100 pages of pro-string theory hype, from Polchinski (two contributions), Silverstein, Kane and Quevedo. As usual with Kane, there’s a string theory “prediction” of the gluino mass (1.5 TeV +/- 10-15%) which has already been falsified. All I could find on the side of substantive criticism of string theory was in Carlo Rovelli’s contribution (preprint version here), and mainly in a single paragraph:

String theory is a living proof of the dangers of excessive reliance on non-empirical arguments. It raised great expectations thirty years ago, promising to compute all the parameters of the Standard Model from first principles, to derive from first principles its symmetry group SU(3)×SU(2)×U(1) and the existence of its three families of elementary particles, to predict the sign and the value of the cosmological constant, to predict novel observable physics, to understand the ultimate fate of black holes, and to offer a unique, well-founded unified theory of everything. Nothing of this has come true. String theorists, instead, have predicted a negative cosmological constant, deviations from Newton’s 1/r^2 law at sub-millimeters scale, black holes at the European Organization for Nuclear Research(CERN), low-energy super-symmetric particles, and more. All this was false. Still, Joe Polchinski, a prominent string theorist, writes [7] that he evaluates the Bayesian probability of string to be correct at 98.5% (!). This is clearly nonsense.

I won’t spend more time here discussing the conference and the articles in this volume, mainly because I’ve already written a lot about this in previous posts. For a contemporaneous discussion of the conference and Polchinski’s String Theory to the Rescue paper, see here and here. There are also interesting blog posts about the conference from Massimo Pigliucci, see here, here and here, and a Quanta piece by Natalie Wolchover here. For a discussion of Sean Carroll’s Beyond Falsifiability contribution, see here (and discussion here and here). For a discussion of Eva Silverstein’s contribution, see here.

Update: A few more links to material about the Munich conference: Jim Baggott here and here, Andrew Gelman here, Davide Castelvecchi here, and the conference website (with videos) here.

Update: Looking at the Preface, I notice that the editors claim:

Additional contributions were solicited by the editors with the aim of ensuring as full and balanced presentation as possible of the various positions in the debate.

With regards to string theory, the one additional contribution in the volume is from string theorist Eva Silverstein, so evidently the editors felt that balance required yet more on the pro-string theory side….

Update: I mischaracterized Polchinski’s calculation of the probability that string theory is correct as 98.5%. More accurately, he claims that the probability is “over 3 sigma” (i.e. over 99.73%).

Update: I finally got around to watching the videos of the panel discussions at the workshop (all videos available here). What most struck me about these discussions was the heavily dominant role of David Gross, who was on two of three panels, participating from the audience in the third. On the panels he was on, Gross was speaking far more than anyone else, and rarely if at all would anyone disagree with him. Gross’s point of view is that there is a testability problem with the multiverse, but all is well with string theory (although probably not at Polchinski’s “over 99.73% sure to be true” level). He’s a powerful intellect and a forceful speaker, so it’s not surprising that no one would take him on. But on the topic of string theory I think there are very serious problems with many of the claims he makes (for his arguments of 15 years ago, see the first substantive post of this blog), and the organizers should have found someone willing to challenge him on those.

Posted in Book Reviews | 26 Comments

Not Even Wrong 2.0

Posted on March 31, 2019 by woit

This blog has just passed its 15th anniversary, and there hasn’t been a lot of change in format since the first postings in March 2004 (there hasn’t been a lot of change in string theory either, but that’s a different topic…). I’ve been hearing a lot in recent years from people who have urged me to update the format of the blog, moving to formats more in tune with the way people now use the internet. One innovation in recent years has been that the blog content is available through Apple News.

I’ve decided to follow some more of the advice I have been getting, and have started up a Not Even Wrong Facebook site. No longer will you have to navigate to my WordPress site to access the blog content, instead it will be available the same way most people are now getting their news, through your Facebook News Feed. This will make it much more convenient for everyone to get notified about new posts and share these with others. I’m looking forward to the expanded readership and connections to the rest of the world that becoming part of the Facebook information eco-system will provide.

Update: Just unblocked a lot of comments that somehow were stuck in a moderation queue. Some people don’t seem to understand that for an international blog like this, the date is best calculated according to UTC.

The uniformly hostile response here to the Facebook idea has been extremely reassuring. No, I don’t intend to move the blog to Facebook. The fact that a sizable fraction of the US population in recent years has been getting its news off their Facebook News Feed seems to be one of the main factors in the 2016 collapse of democracy here, and the same thing is happening all over the world. This has also significantly moved along the ongoing destruction of the economic viability of conventional journalism. Going through the exercise of putting up a Facebook site made me aware of some aspects of how Facebook works I’d never realized. For example, on a Facebook post you can only hyperlink text to other Facebook material, not to the outside world.

It has become all too clear just how ugly the world created by Facebook is, that it is a sociopathic organization, and a danger to a healthy democracy. If you must stay in contact with friends and family this way, avoid any engagement with anything else on the Facebook site. Best would be to delete your Facebook account, now.

Update: For a book-length explanation of why you should be concerned about Facebook, see Roger McNamee’s Zucked, reviewed here.

Posted in Uncategorized | 116 Comments

This Week’s Hype

Posted on March 31, 2019 by woit

This week’s hype comes to us courtesy of Scientific American, which, based on this preprint, tells us: Found: A Quadrillion Ways for String Theory to Make Our Universe.

As usual in these things, the only physicists quoted are the authors of the article, as well as some others (Cumrun Vafa and Washington Taylor) who are enthusiastic about the prospects for getting the Standard Model out of “F-theory”. No one skeptical of the idea of F-theory compactifications of string theory (such theorists would not be hard to find…) seems to have been consulted. If such a person had been consulted, he or she might have pointed out:

  • Models like this have been around for over two decades, see for instance this from 23 years ago.
  • They have always come with claims that some sort of connection to experiment was right around the corner. A decade ago there were papers like this one (and promotional pieces like this one) explaining F-theory “predictions” for what would be seen at the LHC, “predictions” that never worked out.
  • This new work doesn’t even bother trying to make “predictions”. It just works backwards, trying to match the crudest aspects of Standard Model, ones determined by a small set of small integers. Given the huge complexity and number of choices of these F-theory constructions, that some number of them would match this set of small integers is not even slightly surprising.
  • The authors seem to argue that it’s a wonderful thing that they have found quadrillions of complicated constructions with this kind of crude match to the SM. The problem is that you don’t want quadrillions of these things: the more you find, the less predictive the setup becomes. What’s being promoted here is a calculation that not only predicts nothing, but provides evidence that this kind of thing can’t ever predict anything. A peculiar sort of progress…

Update: This hype has now been supplemented by the now common phenomenon among string theorists of having their university’s press office put something out promoting string theory. This time it’s the University of Pennsylvania, with a headline assuring us that their university’s physicists are Making sense of string theory, with a discovery that “might change the course of the field.”

Posted in This Week's Hype | 8 Comments

Some Quick Items

Posted on March 25, 2019 by woit

A few quick items:

  • This past weekend I went to see the new film Out of Blue, which sounded promising: a murder mystery based on a Martin Amis book, set in New Orleans, starring Patricia Clarkson, with a plot involving lots of deep ideas about physics. Unfortunately, the film was pretty awful, for a review from a professional, see here. There was a lot of physics, I think intended to add philosophical depth, but it was just the usual Schrodinger’s cat, black holes, dark matter, multiverse mumbo-jumbo. The Variety reviewer appropriately ends her review with

    It makes one feel a little bit embarrassed for the multiverse.

  • Sticking to the sophomoric, I was searching through old boxes of stuff and turned up a paper I wrote, Quantum Theory and Reality, about the interpretation of quantum mechanics for an expository writing class during my first year (1976) of college. While it was my first year, I did have sophomore standing. Rereading the thing, I’m glad to see that I’ve learned a few things since my sophomore year, but on the other hand, some of my views haven’t changed (I still don’t think “hidden variables” work…).
  • Ethan Siegel at Forbes has This is Why The Multiverse Must Exist. By now, all I can do is refer to this FAQ.
  • Results using the full datasets of the LHC Run 2 are starting to appear, some of them in talks given at last week’s Moriond conference in La Thuile. There are summaries available from CMS, ATLAS and LHCb. Referring to the absence of any significant evidence of new particles or anything inconsistent with the SM, in these results and in a new result from BELLE, Jester comments:

    La Thuile: Where Hopes Melt Away.

    This week, there’s another ongoing “Winter” HEP conference (“Winter” I guess means you can go skiing…), at Aspen.

  • I was sorry to hear of the recent death of Jean-Marc Fontaine, at the age of 74. Frank Calegari has an appreciation of Fontaine and his work here.
  • For more positive recent developments in arithmetic geometry, I recommend Peter Scholze’s lecture series at UCLA on Prismatic Cohomology, discussed by Terry Tao here. In related news, this week at MSRI there’s an interesting workshop on Derived Algebraic Geometry and its Applications.
  • For an interview with Eric Weinstein, who, like Sabine Hossenfelder, is always thought-provoking on the great question of why fundamental physics has gone off the rails, see here. I think he may have a point about Tom Lehrer.
Posted in Film Reviews, Uncategorized | 13 Comments

The Shape of a Life

Posted on March 23, 2019 by woit

I just finished reading The Shape of a Life, which is the great geometer Shing-Tung Yau’s autobiography, co-authored with Steve Nadis. It’s quite fascinating, and an essential read for anyone interested in the history of modern mathematics. Yau has been for a long time a central figure in the field of geometric analysis, so this is in some ways as much an autobiography of the subject as well as of the man.

Back in 2010 I wrote here about an earlier volume by Yau and Nadis, The Shape of Inner Space. What I really liked about that book (and discussed in some detail there) was the autobiographical material about Yau. Much of the book though was devoted to topics like string theory attempts to get physics out of Calabi-Yaus, with a discussion that was detailed and accurate, but to my mind often not of great interest (since these attempts don’t work…).

The new book seems to have been written specifically to appeal to me, greatly expanding the autobiographical material of the earlier book, while limiting the discussion of dubious speculative physics. There is still a fair amount about physics, but this time more focused on another of Yau’s interests, the mathematical theory of general relativity.

The book begins with the story of Yau’s early years in Hong Kong, how he managed to survive an impoverished childhood, avoid becoming a duck farmer, and ultimately find a way to get to the US and graduate study in mathematics at Berkeley. It’s a compelling story of that period and those places. It’s also about the best example I can think of to show how bringing someone with undeveloped talent into the environment of a first-rate research university can change their life, liberating them to accomplish great things, with dramatic impact on their intellectual development as well as that of a whole field.

Yau has always had a deep interest in the history of mathematics, and the story he tells of his intellectual development explains in detail how his own work and ideas grew out of earlier strands of thought. Even as a graduate student, he had started to develop the point of view that has been so fruitful in geometric analysis, using the study of non-linear partial differential equations to prove theorems about geometry and topology. Besides his proof of the Calabi conjecture, this ultimately led to the proof of the Poincare conjecture, a story Yau explains in detail.

Over the years Yau has been involved in various controversies over priority for mathematical results. In this book he doesn’t shy away from discussing these, but generally gives a measured explanation of his point of view on what happened. There’s also a fair number of often amusing stories about mathematicians and the math community that liven up the history. For one sort of example, there are Yau’s descriptions of his culture clash with the long-haired, pot-smoking Berkeley of 1969. For another, here’s a story about Richard Hamilton (of whom Yau has a very high opinion) and his 1982 lectures at the IAS:

Hamilton, who had come from Cornell, stayed for a week in an IAS apartment. At the end of his stay, the chief math secretary was livid because Hamilton had made a huge mess of the apartment, and it took a long time to clean up the place. On the other hand, he had given some wonderful talks, and collaborations between Hamilton, my students, and me picked up from that time forward. So, on balance, his visit would have to be called a great success. Hamilton may have posed some challenges to the cleaning and janitorial staff, but he had posed even more consequential challenges to the mathematics community, some of which were taken up by members of my group.

Yau is generally considered a major figure not just for his research, but also as a politician of the mathematics community, deeply involved for many years in efforts to build or expand research centers, here and in China. A recent example is the creation of the CMSA at Harvard. He has a lot to say about the stories of these efforts, and he definitely does not do so with the style of the politician careful to offend no one. In this book you get Yau’s honest, unvarnished version of what happened, as well as his analysis of some general problems, and I won’t be surprised if some people take offense at this material.

One thing there’s perhaps a bit too much of in the book are the references to his conflicts with his advisor Shiing-Shen Chern (which I’d somehow never heard about before). A major touching theme though throughout the book is that of fathers, sons and traditions of filial piety. There’s a lot about Yau’s father (who Yau very much looked up to) and quite a bit about his sons. On the mathematical side, there’s a lot about his numerous students, many of whom have gone on to important academic careers. As his academic father, Chern also fits into this theme, although not so felicitously. At the end of the book, Yau looks forward to his own future as, like Chern before him, the grand old man of the field. He’s planning more teaching and less research, and taking pleasure in his mathematical legacy and progeny.

Posted in Book Reviews | 7 Comments

This Month’s Hype

Posted on March 14, 2019 by woit

Physics Today seems to have decided to deal with Sabine Hossenfelder’s criticism of a future collider by publishing the least credible possible response: a column by Gordon Kane arguing that string theory predicts new particles of just the right mass to be likely beyond the LHC reach, but accessible to a higher-energy proton-proton machine.

In the column, we learn that:

In recent years there has been progress in understanding those [string theory] models. They predict or describe the Higgs boson mass. We can now study the masses that new particles have in such models to get guidance for what colliders to build. The models generically have some observable superpartners with masses between about 1500 GeV and 5000 GeV. The lower third or so of this range will be observable at the upgraded LHC. The full range and beyond can be covered at proposed colliders. The full range might be covered at a proton–proton collider with only two to three times the energy of the LHC. One important lesson from studying such models is that we should not have expected to find superpartners at the LHC with masses below about 1500 GeV.

Kane has a long history with this kind of thing at Physics Today, publishing there back in 1997 much the same sort of argument, in an article entitled String Theory is Testable, Even Supertestable. According to the Kane of 1997, a generic “prediction of string models” was a gluino at around 250 GeV, just beyond the Tevatron limits of the time. Thirteen years later, Physics Today had him back, publishing an article entitled String theory and the real world. I don’t have the time to do a full search, but, by 2011 after the first LHC results came in, Kane had a string theory prediction of a gluino mass at 600 GeV, or “well below a TeV”.

As better LHC results have come in, each time Kane has issued a new “string theory prediction” that the mass is a bit higher, just about to appear at the next round of LHC results. The last version of this I had seen (see here), was from 2017 and predicted “that gluinos will have masses of about 1.5 TeV”. This is already disconfirmed and out of date, with Kane now telling us “between about 1500 GeV and 5000 GeV.”

For some other evidence of how Kane deals with the problem of having predictions falsified, one can compare the 2000 and 2013 versions of his popular book on SUSY, an exercise I went through here.

At this point, the argument that we need a new collider because “string theory predictions” say that it will see gluinos has zero credibility. I don’t know of any other theorist besides Kane who believes such a thing. That Physics Today is publishing this is just mystifying. Perhaps a collider skeptic there has come up with this as a clever way to back the Hossenfelder side of the argument.

There are some other odd things in the piece, one that stuck out for me was this bizarre claim about recent history:

We now know that if Fermilab and the US Department of Energy had taken the Higgs physics more seriously, the Tevatron would have discovered the Higgs boson years before the Large Hadron Collider did.

I see Will Kinney has more about this on Twitter.

Update: More commentary on this from Jon Butterworth and Sabine Hossenfelder.

Posted in This Week's Hype | 31 Comments

In it for the Long Haul

Posted on March 8, 2019 by woit

The CERN Courier today has a long interview with the omnipresent Nima Arkani-Hamed, discussing the current state of HEP physics. About the motivations for a next-generation collider project, I’m pretty much in agreement with him: the main argument is for a Higgs factory that would allow a much more detailed study of the Higgs, and if at all possible, an appropriate machine should be built (see more here). He agrees that the SUSY and extra dimensions models used to get people excited about the LHC can’t reasonably be used again for a higher-energy machine:

Is supersymmetry still a motivation for a new collider?
Nobody who is making the case for future colliders is invoking, as a driving motivation, supersymmetry, extra dimensions or any of the other ideas that have been developed over the past 40 years for physics beyond the Standard Model. Certainly many of the versions of these ideas, which were popular in the 1980s and 1990s, are either dead or on life support given the LHC data, but others proposed in the early 2000s are alive and well.

The last reference is to his favored split SUSY models, which I think few people besides him find compelling.

About WIMP dark matter he seems to be claiming that a 100 TeV machine has always been what is needed to find it:

There is a funny perception, somewhat paralleling the absence of supersymmetry at the LHC, that the simple paradigm of WIMP dark matter has been ruled out by direct-detection experiments. Nope! In fact, the very simplest models of WIMP dark matter are perfectly alive and well. Once the electroweak quantum numbers of the dark-matter particles are specified, you can unambiguously compute what mass an electroweak charged dark-matter particle should have so that its thermal relic abundance is correct. You get a number between 1–3 TeV, far too heavy to be produced in any sizeable numbers at the LHC. Furthermore, they happen to have miniscule interaction cross sections for direct detection. So these very simplest theories of WIMP dark matter are inaccessible to the LHC and direct-detection experiments. But a 100 TeV collider has just enough juice to either see these particles, or rule out this simplest WIMP picture.

I don’t remember ever hearing, pre-LHC, from him or anyone else, this argument that the most likely WIMP dark matter models are inaccessible to the LHC or to direct detection experiments. For many years, most of the direct detection experimental results came with plots showing a “prediction” of SUSY WIMP dark matter (see for example here, figure 5), in a mass range of 100-500 GeV, at a cross section measurable (and now ruled out by) experiments like XENON1T (see here).

Arkani-Hamed likes to make the following argument, which I think most current HEP theory graduate students may find hard to swallow:

How do you view the status of particle physics?
There has never been a better time to be a physicist. The questions on the table today are not about this-or-that detail, but profound ones about the very structure of the laws of nature. The ancients could (and did) wonder about the nature of space and time and the vastness of the cosmos, but the job of a professional scientist isn’t to gape in awe at grand, vague questions – it is to work on the next question. Having ploughed through all the “easier” questions for four centuries, these very deep questions finally confront us: what are space and time? What is the origin and fate of our enormous universe? We are extremely fortunate to live in the era when human beings first get to meaningfully attack these questions. I just wish I could adjust when I was born so that I could be starting as a grad student today!

There’s something to be said for entering a field at a time when it is finally able to “meaningfully attack” difficult and fundamental questions. The issue though is whether anyone has any good ideas that will make headway against such questions. The Standard Model was in place by the mid-70s, and by the time I was a graduate student in the early 80s, the “what are space and time? what is the origin and fate of our enormous universe?” questions were already on everyone’s mind as the next things to be thinking about. Starting in 1984, the superstring revolution promised a way to answer these questions.

35 years later, the current generation of graduate students has the same questions to think about, but a long history of failed attempts to consider. In addition, there’s the sad story of the unwillingness of leading figures of the field to admit to the failure of the 1984 revolution, and widespread multiverse pseudo-science (often promoted by Arkani-Hamed) to overcome. The only argument that I can see that this is a good time to start an HEP theory career is that it’s hard to see how things can get worse…

For some commentary about the interview by Tommaso Dorigo, concentrating on the positive case for a new collider as a tool to study the Higgs, see here.

Posted in Uncategorized | 34 Comments

This Week’s Hype

Posted on March 5, 2019 by woit

In recent years string theorists have been having trouble getting taken seriously by the media, a problem they’ve been trying to deal with by enlisting the PR departments of their universities to help. Following Princeton and Stanford, today’s the turn of the string theorists at Northeastern, who had their press office put out a press release announcing “Northeastern team uses string theory to explain the fundamental nature of the universe.”

As usual, this is just pure, unadulterated hype. It’s based on a PRL publication, also available as this preprint. I usually try to avoid this sort of editorializing, but I’m actually shocked to see that PRL is now publishing this sort of thing, which is infinitely far from having any connection to conventional science.

Posted in This Week's Hype | 9 Comments

A Few Items

Posted on February 28, 2019 by woit

A few things that may be of interest:

  • The Perimeter Institute has a new director, Rob Myers, succeeding Neil Turok. Myers is very much a mainstream theorist, and Perimeter over the years has been converging with the mainstream, from a very non-mainstream initial state. While Turok has taken the view in recent years that theoretical physics is in “a deep crisis”, Physics World has:

    Myers says there are many opportunities in theoretical physics, mostly thanks to the vast amounts of data that are being collected by various experiments such as CHIME, EHT and the LIGO gravitational-wave detectors in the US. Yet Myers doesn’t believe that theoretical physics is in “a deep crisis” as Turok once admitted. “Particle physics is somewhat at a crossroads,” he says. “Describing it as a crisis is slightly dramatic, but I would agree that people have been relying on the status quo for too long and relaying on certain models from decades ago.”

    Indeed, Myers now challenges researchers to think in new ways. “Young people are the future and we want to instill in them to question the status quo,” he adds. “After all, it is the people here that make the PI such a special place.”

  • Speaking of challenges to the status quo, it seems that Sabine Hossenfelder now has a contract for her second book, topic not yet revealed.
  • For the latest news from the Swampland, see this twitter thread from Will Kinney. He explains how the “Swampland conjecture” was meant to kill off the string theory multiverse, but this conjecture got in trouble:

    So by getting rid of the multiverse, we have also gotten rid of known physics like the Higgs boson. Merde!

    It was replaced by a fix, the “refined Swampland conjecture”, but Kinney has a new paper in PRL (arXiv link here) showing this fix doesn’t solve the multiverse problem for string theory:

    This means that, as soon as we fix up the Swampland Conjecture so it doesn’t trivially rule out known physics like the Higgs, we inevitably get an unwelcome passenger: the string multiverse!

    This is important because it looked like the Swampland Conjecture was likely to free us from the multiverse and associated awful stuff like the Anthropic Principle. Not so, we’re still stuck with it. Sorry.

  • John Baez has a popular article at Nautilus about his new-found love for algebraic geometry, as an explanation of the relation of classical and quantum. The more technical version is a series of posts here.

Update: Arnold Neumaier has posted at the arXiv a series of three papers discussing his “thermal interpretation” of quantum mechanics (see here, here and here). While I find many of the points he seems to be making compelling, I haven’t had time to think seriously about what the problems of his approach might be (and there’s a long history of online discussions between him and others which would be a good place to start). Neumaier in the papers explicitly asks for discussion of them at physicsoverflow.org, and there are now posts there for this purpose (here, here and here). I look forward to following any discussion with him over there. He also has a website devoted to this topic here, which has some links to earlier discussions.

Update: There’s a new issue of Inference out. As usual, some interesting pieces from people not usually heard from in a non-technical venue. No sign of the pro-intelligent design/climate denialism agenda that they’ve been accused of having (see here). Pieces specifically relevant to some of the obsessions of this blog are a review by Glashow of Lost in Math, and a piece by David Roberts on the Mochizuki/Scholze/Stix story.

Posted in Swampland, Uncategorized | 3 Comments

The Mathematical Question From Which All Answers Flow

Posted on February 19, 2019 by woit

I’m beginning to suspect that there are actually (at least) two different theoretical HEP physicists named Nima Arkani-Hamed out there. One of them (who I’ll call Nima1) believes the way to understand the fundamental nature of physical reality involves extremely complicated extensions of the Standard Model, with large numbers of parameters tuned to avoid conflict with observation, and possibly hundreds or thousands of extra fields thrown in for good measure. He also seems to like the multiverse and anthropic explanations. I have a lot of disagreements with Nima1, most recently discussed here.

The second Arkani-Hamed (Nima2) has a completely different point of view, one quite close to my own, although he may be even more of a mathematical mystic than I am. Natalie Wolchover has recently talked to Nima2 and written about it for the New Yorker. Nima2 is in love with the deep mathematical structure of physics and the way it appears in different aspects:

Nima Arkani-Hamed, a physicist at the Institute for Advanced Study, is one of today’s leading theoreticians. “The miraculous shape-shifting property of the laws is the single most amazing thing I know about them,” he told me, this past fall. It “must be a huge clue to the nature of the ultimate truth.”

Wolchover expands on this idea of multiple ways of expressing the same underlying mathematical structure:

The existence of this branching, interconnected web of mathematical languages, each with its own associated picture of the world, is what needs to be understood.

This web of laws creates traps for physicists. Suppose you’re a researcher seeking to understand the universe more deeply. You may get stuck using a dead-end description—clinging to a principle that seems correct but is merely one of nature’s disguises. It’s for this reason that Paul Dirac, a British pioneer of quantum theory, stressed the importance of reformulating existing theories: it’s by finding new ways of describing known phenomena that you can escape the trap of provisional or limited belief. This was the trick that led Dirac to predict antimatter, in 1928. “It is not always so that theories which are equivalent are equally good,” he said, five decades later, “because one of them may be more suitable than the other for future developments.”

Today, various puzzles and paradoxes point to the need to reformulate the theories of modern physics in a new mathematical language. Many physicists feel trapped. They have a hunch that they need to transcend the notion that objects move and interact in space and time. Einstein’s general theory of relativity beautifully weaves space and time together into a four-dimensional fabric, known as space-time, and equates gravity with warps in that fabric. But Einstein’s theory and the space-time concept break down inside black holes and at the moment of the big bang. Space-time, in other words, may be a translation of some other description of reality that, though more abstract or unfamiliar, can have greater explanatory power.

Nima2 is obsessed with exactly the same mystical mathematical issue that I am: what’s the right mathematical question that has as answer the Standard Model and GR?

To Arkani-Hamed, the multifariousness of the laws suggests a different conception of what physics is all about. We’re not building a machine that calculates answers, he says; instead, we’re discovering questions. Nature’s shape-shifting laws seem to be the answer to an unknown mathematical question…

Arkani-Hamed now sees the ultimate goal of physics as figuring out the mathematical question from which all the answers flow. “The ascension to the tenth level of intellectual heaven,” he told me, “would be if we find the question to which the universe is the answer, and the nature of that question in and of itself explains why it was possible to describe it in so many different ways.” It’s as though physics has been turned inside out. It now appears that the answers already surround us. It’s the question we don’t know.

I’m not sure the Amplituhedron is the right path to the “tenth level of intellectual heaven” and finding the “mathematical question from which all the answers flow”, but I’m completely sympathetic with Nima2’s motivation and quest.

Posted in Uncategorized | 16 Comments