Are Physical Laws Inevitable?

The last couple days have seen various discussions online generated by a piece at Quanta Magazine with the dubious headline Why the Laws of Physics Are Inevitable and an even worse sub-headline claiming “physicists working on the ‘bootstrap’ have rederived the four known forces” (this is utter nonsense). For some of this discussion, see Sabine Hossenfelder, John Baez and Will Kinney.

One reason this is getting a lot of attention is that the overall quality of reporting on math and physics at the relatively new Quanta Magazine has been very high, a welcome relief from the often highly dubious reporting at many mainstream science media outlets. The lessons of what happens when the information sources society relies on are polluted with ideologically driven nonsense are all around us, so seeing this happen at a place like Quanta is disturbing. If you want to understand where this current piece of nonsense comes from, there is an ideology-driven source you need to be aware of.

A major line of defense of their subject by string theorists has essentially been the claim that, while it may lack any experimental support, string theory is “the only consistent way to combine quantum theory and general relativity”. I’ve often explained what the problem with this is, won’t go on about it again here. Nima Arkani-Hamed is at this point likely the most influential theorist around, for some good reasons. The roots of the problem with the Quanta article lie in taking too seriously the kind of arguments he tends to make in the many talks he gives. He’s trying to make as strong as possible a case for the research program he is pursuing, so unfortunately gives all-too-convincingly a very tendentious take on the scientific issues involved. For more about this, see a posting here about the problems with the recent Quanta article that motivated the latest one.

Debates over generalities about whether the “laws of physics are inevitable” are sterile and I don’t want to engage in them here, but I thought it would be a good idea to explain what the serious ideas are that Arkani-Hamed and others are trying to refer to when they make dubious statements like “there’s just no freedom in the laws of physics”. Here’s an attempt at outlining this story:

Quantum mechanics and special relativity:

A mathematically precise implication of putting together fundamental ideas about quantum mechanics and special relativity is that the state space of the theory should carry a unitary linear representation (this is the QM part) of the Poincaré group (this is the special relativity part). You also generally assume that the time translation part of the Poincare group action satisfies a “positive energy” condition. To the extent you can identify “elementary particles”, these should correspond to irreducible representations. The irreducible unitary representations of the Poincaré group were first understood and classified by Wigner in the late 1930s. My QM textbook has a discussion in chapter 42. If you impose the condition of positive energy and for simplicity consider the case of non-zero mass, you find that the irreducible representations are classified by the mass and spin (which is 0,1/2,1,3/2, etc.). Non-interacting theories are completely determined by the representation theory and exist for all values of the mass and spin.

Extensions of Poincare and the No-go theorem of Coleman-Mandula

To get further constraints on a fundamental theory, one obvious idea is to extend the Poincaré group to something larger. States then should transform according to unitary representations of this larger group, carrying extra structure. Restricting to the Poincaré subgroup, one hopes to get additional constraints on which Poincaré representations can occur (they’ll be those that are restrictions of the representations of the larger group). The problem with this is the Coleman-Mandula theorem (1967) which implies that for interacting theories the larger group can only be a product of Poincaré times an internal symmetry group. Representations will just be products of the Poincaré group representations and representations of the internal group, with space-time symmetries and internal symmetries having nothing to do with each other. This is why the Quanta headline about “rederiving the four known forces” is nonsense: the three non-gravitational forces are determined by internal symmetries, have nothing to do with what the Quanta article is describing, work on space-time symmetries.

One way to avoid the Coleman-Mandula theorem is to work with not Lie algebras but Lie superalgebras. Here you do get a non-trivial extension of the Poincaré group and a prediction that Poincaré representations should occur in specific supermultiplets. The problem is that there is no evidence for such supermultiplets.

Another possible extension of the Poincaré group is the conformal group. Here the problem is that the new symmetry implications are too strong, they rule out the massive Poincaré group representations that we know exist. One can work with the conformal group if one sticks to massless particles, and this is what the methods advertised in the Quanta article do.

The idea that our fundamental space-time symmetry group is the conformal group is mathematically an extremely attractive one, with the twistor picture of space-time playing a natural role in this context. I strongly suspect that any future truly unified theory will somehow exploit this. Unfortunately, as far as I know, no one has yet come up with a way of exploiting this symmetry consistent with what we know about elementary particles. Likely a really good new deep idea is missing.

Quantum field theory

To get stronger constraints than the ones coming from Poincaré symmetry, one needs to decide how one is going to introduce interactions. One way to go is quantum field theory, with a principle of locality of interactions. This gets encoded in a condition of (anti)commutativity of the fields at space-like separations, which then implies various analyticity properties of correlation functions and scattering amplitudes. The analyticity properties can then be used to prove things like the CPT theorem and the spin-statistics theorem, which provide some new constraints.

Given a method of constructing a Poincaré invariant quantum field theory, typically done by choosing a set of classical fields and a Lagrangian, one can try and realize the various possible Poincaré group representations as interacting theories. What one finds is that, for spins greater than two one runs into various seemingly intractable problems with the construction. One also finds exceptionally beautiful theories in the spin 1/2 and spin 1 cases that exhibit an infinite dimensional group of gauge symmetries. An example of these is the Standard Model. Unfortunately, we know of no principle or symmetry that would provide a constraint that picks out the Standard Model. If we did, we might be tempted to announce that the principle or symmetry is “inevitable” and thus the “laws of physics are inevitable”. We’re not there yet…

Amplitudes and the S-matrix philosophy
In the S-matrix philosophy one takes the analyticity properties as fundamental, working with amplitudes, not local quantum fields. The 1960s version of this program (also often called the “bootstrap” program) was based on the hope that certain physically plausible analyticity assumptions would so tightly constrain the theory of strong interactions that it was essentially uniquely determined. This didn’t work out. In his recent introductory lecture for his course at Harvard, Arkani-Hamed explains why. The research program he and others are currently pursuing is in some sense a modernized version of the failed 60s program. The hope is that new structures in amplitudes can be found that will replace the structures one gets from local quantum fields.

Amplitudes based arguments about, for instance, why you don’t see fundamental higher-spin states, and why spin 1/2 particles have forces of the kind given by gauge theory have a long history, see for instance work on massless particles by Weinberg in the mid-sixties and Weinberg-Witten in 1980.

As far as I can tell, the work referred to in the Quanta article gives new amplitudes-based arguments of this kind for massless particles, exploiting conformal symmetry. It’s not clear to me exactly what’s new here as opposed to earlier such arguments, or how strong an argument about real world physics one can make using these new ideas. One thing that is clear though is that the Quanta quote that what has been discovered implies that “There’s just no freedom in the laws of physics” is as much nonsense as the “we rederived the four known forces” business.

Update: For some discussion with the author of the Quanta piece, Natalie Wolchover, see the comments starting here.

Update: The Quanta article has been revised, see comments in the comment section here. There Daniel Baumann provides a link to a popular summary of the facts about massless particle interactions that his quotes were about.

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47 Responses to Are Physical Laws Inevitable?

  1. Akhil says:

    What are those “good reasons” that Nima Arkani-hamed is the most influential theorist around? And what are your thoughts on his amplituhedron approach?

  2. Low Math, Meekly Interacting says:

    Thanks for this. I’m sorry you and a few others had to make the effort, needed as it was. I found that article in particular quite a letdown.

  3. Peter Woit says:

    Akhil,
    He has shown excellent taste in moving out of his roots in SUSY phenomenology and instead into mathematical physics. As far as topics in mathematical physics go, looking at amplitudes in twistor space seems like a good thing to be trying. He’s clearly smart and hard-working, an inspiration to many.

    Another “good reason” that I had in mind was that he’s an extremely energetic and compelling speaker, but while this is an important “reason”, maybe it’s not a “good” reason, in the sense of good for the understanding of science.

    About the amplituhedron, the hype campaign back in 2013 and the “Jewel at the heart of physics” business in Quanta at the time was a bit disturbing. It was however so over the top that I thought most people didn’t take it seriously (evidence for this was Scott Aaronson’s blogging about the “diaperhedron”). As a piece of mathematical physics, my reaction to it then was like my reaction to a lot of things: “I don’t have time to sit down and figure out precisely what this is and what it does, so I’ll just wait a few years and see what happens. Either it will genuinely be a huge advance and after things settle down there will be lots of nice places to easily learn the details, or it won’t turn out to be that much, and I’ll have saved a lot of time.” Six years on, this seems to have been a good choice…

    More generally, I’ve been following Arkani-Hamed’s claims that this research on amplitudes is going to replace space-time for over a decade now. At first I was impressed, but over the years it has become clear that there’s a massive gap between what he actually has and the claims he likes to start his talks with, a gap which shows no signs of narrowing. He often makes very clear that he himself recognizes that what he’s doing is trying to puff up his own interest in the subject in order to keep going.

    I really wish he and Baumann would start acting responsibly and stop the hype campaign, or at least stick to only getting it in places like New Scientist.

  4. Workerpleb says:

    I get the sense that articles like this are motivated in large part by research funding pressures.

  5. Peter Woit says:

    Workerpleb,
    I don’t know about Baumann, but Arkani-Hamed definitely doesn’t need the money. He has a $3 million prize, and a very highly paid position to do full-time research. Actually, in many of his talks he explains clearly the motivation for the hype: it’s to motivate himself. Not easy to get up in the morning and do hard, tedious calculations telling yourself “if I work hard I’ll find the value of the 3rd loop term in this scattering amplitude”. A lot more effective motivation to tell yourself and everyone else you’re doing this because it’s going to kill off space and time and revolutionize physics. The problem is that others start believing you…

  6. Boyer Lindquist says:

    That Quanta article is also misleading from a historical perspective. There one reads: “As the Nobel Prize winner Steven Weinberg showed in 1964, the existence of a spin-2 particle leads inevitably to general relativity.” It’s true that Weinberg did this, but he wasn’t the pioneer as the Quanta article seems to imply, e.g., Pauli & Fierz or even Feynman worked on the matter some time before.

  7. Akhil says:

    Peter,
    As you said Nima is clearly smart and hard-working, an inspiration to many (including myself) but your response makes a lot more sense. I wonder what will be a more productive/sensible way to motivate yourself than making over-the-top claims (as Nima admits)? How do others like Weinberg, Witten, Atiyah motivate themselves? What about pure mathematicians in general, their work is not immediately connected to physical world, forget about replacing space-time. What do they wake up saying themselves? Your thoughts Peter?

  8. DB says:

    Peter,
    thanks a lot for your comments and for answering Akhil question. I was going to ask the same.
    Arkani-Hamed is a very smart and hard working individual, no doubt about that.
    But I’ve got the feeling that he knows that the HEP theoretical world has found a brick wall at a dead end street.
    It was either Sabine or you who already mentioned that there were suspicions about that.
    The question is why doesn’t he say so. Not sure if it’s related to money, ego or professional position… or another option I can’t think of. He already has enough money to live as you say, he doesn’t show too much ego (at least in public appearances), and his position in the teaching sphere is totally assured, so…
    what’s left?
    I think that what he’s doing, imagining it would come to a successful end, is just solving technicalities, not anything that could revolutionize theoretical physics or bring in new ideas/theories, like the substitution of space/time with something else.
    He was even asked once by David Gross if he thought that “God” spoke in the language of polytopes, to which he obviously answered “No”.
    What he’s doing is not a waste of time by any standard, but something far, very far away from what he pretends to sell at his conferences.
    Which is something that leaves me thinking about some ethical aspects of the whole thing.
    Anyway, the key of this all is, as you say, that people believe in this kind of things.
    When the amplituhedron idea came out, even Witten was very excited about it.

    https://www.quantamagazine.org/physicists-discover-geometry-underlying-particle-physics-20130917/

    But as time has gone by, it’s clear that it is an amazing new way to calculate amplitudes
    (and Nima deserves great compliments for that), but it ain’t any physics revolution at all by any standard of the imagination.

    I just wonder when everyone in that world will acknowledge that they’re totally stuck, and that they have to go back to the blackboard, rewind two decades, and start re-thinking about all these stuff with a totally new and honest mentality.

  9. Suomynona says:

    Boyer Lindquist,
    I believe Weinberg’s achievement was showing that any QFT of a spin-2 particle must couple to all forms of matter equally, and is essentially the particle manifestation of the equivalence principle. The prior work of Fierz, Pauli, Feynman, et al., did not show such a robust intimate connection between the two concepts.

  10. The problem with all the twistor stuff is that it’s all on shell. You need that for conformal invariance. But massless on-shell loop amplitudes are infrared divergent. Any regularization (dimensional or massive or off-shell) destroys the conformal invariance. So these guys write the explicit integrands for amplitudes, but can’t integrate them.

    A related problem is that “on-shell states only” means there’s no obvious way to introduce the iε prescription of Stückelberg-Feynman propagators, except for trees, where you can just stick them in by hand for the poles. So you get integrals where you don’t know which contour to choose around the singularities.

  11. Peter Woit says:

    Akhil/DB,
    Mathematicians can also be motivated by wanting to solve great problems. Andrew Wiles I think has said he was motivated to go into number theory by the Fermat problem, and possibly this had some influence on research directions he chose. Once he actually had a serious idea about how to solve the problem, he wasn’t about to talk about it publicly.

    The culture of mathematics is less tolerant of people making vague, unsupported and grandiose claims. But even in physics, behavior like that of Arkani-Hamed is quite unusual. While lots of people may be motivated by hoping to find a new way of thinking about space and time, they don’t normally spend long parts of their talks going on about this. Also odd is the way he goes on about “this is the most exciting time ever to do this kind of theoretical physics”. I don’t doubt for a minute that he believes what he is saying, but it’s not very credible, and I suspect most experts listening to him are well aware of this.

    It seems likely that the current amplitudes program suffers from the same problem as the sixties version: by giving up local quantum fields and gauge symmetry you’re giving up too much fundamental structure. You never were going to understand the strong interactions that way, just as I suspect you’re never going to understand quantum gravity without some new fundamental idea about the symmetries of short-distance space-time degrees of freedom. One promising thing about the amplitudes program is the use of twistors and conformal symmetry. On the other hand, I don’t see polytopes as a promising fundamental idea. But who knows, advances are made by those who believe in them, maybe something will come of this and it’s great that some are pursuing these ideas.

  12. Boyer Lindquist says:

    Suomynona,
    Thanks for the reply. I agree that Weinberg’s approach was much clearer. But I would like to note an interesting paper on this subject, published by W. Thirring, “An alternative approach to the theory of gravitation,” Annals of Physics (1961), where he also gave a field-theoretic approach to GR and concluded: “Regarding the two cornerstones of general relativity’s the field theoretic approach (1) gives the equivalence principle as a result and not as a postulate (2) it replaces the general covariance principle by gauge invariance (…)”.

  13. Peter Woit says:

    Warren Siegel,

    Thanks! It’s very helpful to hear not just about the positive hopes for ideas, but also about the main problems they face.

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  15. Suomynona says:

    Boyer Lindquist,
    Weinberg actually cites Thirring’s paper in a related 1965 paper (PR 138 B988), and has this to say about it:

    In criticism of these articles we may say first that they generally seem to be based on specific Lagrangians, and secondly, that there does not seem to be much point in defining the spin of a field without being able to tie the definition to the physically relevant representations of the inhomogeneous Lorentz group, i.e., the one-particle states. In our work everything rests on the known transformation properties of the operators which destroy and create physical particles, and of course we make no use of the Lagrangian formalism.

    Weinberg’s approach in his 1964 paper (PR 135 B1049) still appears more general than Thirring’s and is rooted in a quantum context (the S-matrix), whereas Thirring appears to start from classical considerations.

  16. 4gravitons says:

    For what it’s worth, I’m fairly certain none of the results the Quanta article describes invoke conformal symmetry. Aside from the mention of Nima’s work on cosmological correlators with Baumann, Lee, and Pimentel, the article looks like it’s mostly talking about Laurentiu Rodina’s work. You can look at the conditions he imposes, they don’t typically involve conformal symmetry in any crucial way (except in that they involve on-shell massless particles and thus spinor-helicity formalism, so if that’s all you meant I apologize for misunderstanding you).

    I agree that the headline and a lot of the language in the article is overblown, these people aren’t deriving the SM gauge group or anything like that. All they’re doing is looking at what sets of minimal conditions can be enough to fix tree-level amplitudes in various theories. What’s interesting is that these conditions can be quite light: often a few constraints from UV behavior or soft theorems are enough to specify a class of amplitudes without invoking, for example, unitarity.

  17. Peter Woit says:

    4gravitons,
    Thanks. I had assumed the reference to
    https://arxiv.org/abs/1811.00024
    indicated that the methods of that paper which used conformal symmetry were involved.

    If that’s not the case I’m even more mystified by the motivation for this article. The only reference to Rodina’s work is to the more than 5 year old
    https://journals.aps.org/prd/abstract/10.1103/PhysRevD.90.084048
    which is described as an update of Weinberg. Rodina does seem to have very new results of this sort, e.g.
    https://arxiv.org/abs/1910.12850
    but those don’t seem to be mentioned.

  18. 4gravitons says:

    I suspect Nima was her primary contact. That would explain why she only asked Rodina about his older work with Nima, why she threw in the cosmological correlator story (which is kind of about the same thing, but a bit distant), and why she didn’t mention related work by other amplitudes people like Rutger Boels. I don’t think it was intended to be an article about any specific work so much as the general theme, but it is weakened a lot by not including more of the history and background. (Which by the way, your post is a good treatment of! The world needs more explainer posts!)

    For what it’s worth Warren’s point isn’t really applicable to any of the work referred to here, since it’s a) all tree level and b) the one that uses conformal symmetry is for correlators and thus off-shell. It’s potentially a valid criticism to the amplituhedron story but that’s not really the topic at hand.

  19. Natalie Wolchover says:

    Peter,
    The headline, I grant you, is overblown. Writers don’t get to choose headlines. But as for the article, some people seem to be reading into it things it never says and ignoring things it does say. I would wager that these readers know too much for this article, and don’t have a sense of what lay readers know and don’t know. This article is for them — for people who have no clue about the scheme that nature’s building blocks fit into, people who think “photons” and “gluons” are like animals you might come across in a zoo that can look and act any possible way. There is an astonishing aspect to fundamental physics that these folks are missing out on, and excuse me for daring to try to explain it to them.

    The article does not say that this is the only possible way the universe could be; in fact, it discusses some of the instances where the universe has “creative license,” as I put it — e.g. with massive spin-½ particles and spin-0 particles, where there are very few constraints. But in other instances, the options are incredibly constrained — so much more than most people appreciate. So rather than getting upset thinking I’m making some kind of anti-empirical claim, maybe just step back and try to remind yourself how interesting it is — how amazing it must have seemed to you when you learned about it in grad school — that a massless spin-2 particle must uniquely be the graviton. That the spin possibilities are so limited. Etcetera. The person on the street doesn’t know about these things, and it’s worth telling them.

    If you’re interested, the references that I was most often pointed to (aside from the classic Weinberg paper) are:
    Benincasa and Cachazo (2008) https://arxiv.org/abs/0705.4305
    Schuster and Toro (2008) http://arxiv.org/abs/0811.3207
    McGady and Rodina (2014) http://arxiv.org/abs/1311.2938
    Best,
    Natalie

  20. Peter Woit says:

    Natalie,

    I don’t at all have a problem with the way you were trying to explain remarkable facts about constraints on theories of massless particles. This is a really tricky business and note that in my own attempt here to write something, even for a more sophisticated audience, I basically gave up. I was hoping to say more than what’s in the next to last paragraph, but after thinking about it for a while decided it was just too hard to say something both true and insightful about this topic, even assuming a lot of background.

    I also don’t have a problem with the “are the laws of physics inevitable?” framing or the headline of your piece. I used this kind of title for what I wrote also, to get attention and be provocative (seems to have worked, this posting is getting more attention than usual). Sabine Hossenfelder makes the obvious accurate counter-argument about what is wrong with this, but it remains true that it’s remarkable what you can say based on a couple deep ideas and consistency, without even looking at the real world.

    The huge problem here is the sub-headline. It’s just completely wrong, basically everything about it. And probably an order of magnitude more people are going to read it than read the whole piece. Over the years I’ve seen this time and time again in science journalism: pretty good article, which goes up to the line of being wrong, to make a point, but doesn’t cross it. Whoever writes headlines thinks it’s their job to jazz things up and get attention, so they happily cross the line and write something completely wrong. I don’t know what happened here or what Quanta’s procedures are, but it would be a good idea to think through whether you can do better than others and avoid this kind of thing.

    Honestly, if this sub-headline had appeared on an article a most other places I would probably have just ignored it, figured it best to not give it more attention. A lot of the complaints you’re getting here are due to the fact that people have a very high opinion of your work and that of others at Quanta. Keep up the good work, but think about whether you can do better with the headlines/sub-headlines!

    Peter

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  22. Squarkino says:

    In https://arxiv.org/abs/1709.04891 , Arkani-Hamed spoke of ‘deriving string theory’ from first principles. How much progress has been made on that front?

  23. Peter Woit says:

    Squarkino,
    While the idea of “deriving” string theory from some constraints on amplitudes sometimes gets mentioned, that doesn’t seem to actually have anything to do with the work you link to or other recent amplitudes work discussed in Quanta articles. The questions about string theory amplitudes have to do with an infinite tower of massive states and short distance behavior, most of the new amplitudes methods are for theories of massless particles.

    It’s remarkable the extent to which currently fashionable research on quantum gravity (for instance Arkani-Hamed’s idea that one can get rid of space and time using things like the amplituhedron or “it from qubit” ideas for emergent gravity) has little or nothing to do with string theory.

  24. Natalie Wolchover says:

    Peter,
    Fine, you didn’t like the subhed. It’s hard to summarize these ideas in an appealing sentence. Does that critique really justify calling this piece “ideologically driven nonsense”? Why be so overly critical? If you think this stuff is indeed remarkable and worth explaining, why not say so in your original post — with the caveat that you don’t like the display copy — rather than calling it nonsense and insinuating that I’ve been taken for a ride by ideologues? It’s unkind and untrue, and unfortunately the clarifications in your comment will be seen by virtually no one.
    Natalie

  25. Peter Woit says:

    Natalie,

    My apologies for not making it clear that I was mostly talking about the subhed. In the main text though, the paragraph which expands the subhed
    “Thus, by thinking through the constraints placed on fundamental particle interactions by basic symmetries, physicists can understand the existence of the strong and weak forces that shape atoms, and the forces of electromagnetism and gravity that sculpt the universe at large.”
    has the same problem (the bootstrappers have zero to say about internal symmetries and thus the existence of the SM forces). I’ll add something to the end of the posting pointing to our discussion here.

    The problem with the subhed (or that paragraph I quoted) isn’t that it’s not to my taste. Note that, the day before I wrote anything, both John Baez and Will Kinney found this so problematic and remarkable that they wrote Twitter threads about it (there was also the more general Sabine Hossenfelder criticism). I think any physicist who knows anything about this subject and read the subhed probably had the same reaction: why is such a nonsensical claim appearing in Quanta, which normally is quite reliable? My posting was an attempt to provide some background for anyone asking themselves that question, in both the positive sense of pointing to important technical results and in the negative sense of pointing to the motivation behind over-the-top claims from theorists.

    Apologies also for the overly vociferous tone of some of the posting, which was aimed not at you, but at the theorists involved. I don’t know Baumann at all, but I don’t understand why any theorist would think it was all right to tell the public that he and his colleagues have shown that “There’s just no freedom in the laws of physics that we have.” The field of high energy physics has suffered greatly from overblown claims by theorists. After 35 years of this, I’m getting both old and testy…

  26. Jack Morava says:

    In general I am a fan of Natalie Wolchover’s work but I think it’s unfair to describe Peter’s remarks as overly critical. Extraordinary claims deserve extraordinary evidence, and one would like to believe that `there is some inevitability of the laws of physics that can be summarized by a short handful of principles that then lead to building blocks that then build up the macroscopic world’. In that case, though, it would be nice to see that short handful of principles.

  27. Jackiw Teitelboim says:

    Dear Natalie,

    I believe your article succeeds well in explaining the notion of a particle’s spin in a quite accessible way, and its role in determining their possible interactions. It’s not quite easy to explain these things to lay-readers, and sometimes even to our students!

    About what people called “hype,” given that lay-readers will always be impressed with quotations from Einstein, a possibility instead of stating ambitious nonetheless unsubstantiated claims would be to cite remark from Einstein’s Autobiographical Notes, particularly the last sentence (but I copy the whole paragraph for completeness):

    There is something else that I have learned from the theory of gravitation: No collection of empirical facts, however comprehensive, can ever lead to the setting up of such complicated equations. A theory can be tested by experience, but there is no way from experience to the formulation of a theory. Equations of such complexity as are the equations of the gravitational field can be found only through the discovery of a logically simple mathematical condition which determines the equations completely or (at least) almost completely. Once one has those sufficiently strong formal conditions, one requires only little knowledge of facts for the setting up of a theory; in the case of the equations of gravitation it is the four-dimensionality and the symmetric tensor as expression for the structure of space which, together with the invariance concerning the continuous transformation-group, determine the equation almost completely.
    —A. Einstein (Autobiographical Notes, 1949)

    Interesting to note that, as you last article at Quanta says that “Einstein arrived at general relativity through abstract thoughts about falling elevators and warped space and time,” you see that Einstein himself in his later life understood quite well how the symmetries of the theory – “continuous transformation-group” – plays a fundamental role.

  28. bertie says:

    I feel quite sorry for scientific journalists covering HEP, after all, what is there to write about that is ‘news’, peraps a little adventurism with headings is forgivable?

  29. Peter Woit says:

    Jackiw Teitelboim,
    What the Einstein quote is referring to (diffeomorphism invariance) and what the amplitudes papers that Natalie Wolchover links to are doing (adding constraints from locality and unitarity to the usual Poincaré group action constraints) are two completely different things. One of the main motivations of the whole amplitudes program is to formulate the theory in a way that gets rid of the action of local symmetries. I recall that in one talk Arkani-Hamed described gauge symmetries with the technical term “crap”. The argument is that local field theory with an infinite-dimensional group of local symmetries is a bad starting point, since it introduces a huge amount of redundancy in the description of nature.

    This is also part of my objection to the text I quoted from the Quanta piece, which seems to imply that what’s different about the work she is discussing involves “the constraints placed on fundamental particle interactions by basic symmetries”, which is kind of backwards.

  30. DrDave says:

    Natalie, I guess as an editor I would simply correct the highly visible line at the top (with a correction note) “physicists working on the “bootstrap” have rederived the four known forces” as it isn’t true. One can argue about the imaginary layperson, and attention grabbing headlines, and so on, one can fob it off on the editor. But, at the end of the day, it isn’t true and it has your name on it. So that’s a really good reason, as a journalist, to correct it. One of the jobs of a journalist is to fix stuff like this. If you don’t, it implies that you have seen the evidence that it is not true and don’t agree with it somehow.

  31. John Baez says:

    It’s pretty strange that the title and subhead of an article – the only parts most people actually read – should be left to crazed hypesters unrestrained by sense of honesty. Imagine that the New York Times had that policy. Would anyone take it seriously?

    But it’s not just that the title and subheading are completely wrong. The quotes of Daniel Baumann in the article are also misleading and make grandiose claims that he did not intend.

    On Twitter I wrote:

    There’s an absolutely wild quote by Daniel Baumann: “There’s just no freedom in the laws of physics that we have.” If he’s shown this, then he’s solved all the biggest questions in fundamental physics and he deserves the next 20 Nobel Prizes. But he hasn’t.

    Daniel Baumann replied:

    I agree its very unfortunate. I spoke in a precise context: that the long-distance interactions of a massless spin-2 particle are those of GR. Everything here is in the context of massless particles. As you said, this is old stuff. I didn’t not mean to imply more. I was just explaining the technical arguments. Didn’t mean to hype anything. Apologies.

    I replied:

    Didn’t Natalie read you your quotes? When I’ve been interviewed for Quanta articles they’ve been pretty good at doing that, which allowed me to fix things. They even had a “fact-checker” for this purpose.

    Whoever writes the headlines, however, seems beyond supervision.

    Daniel Baumann replied:

    No, not this time. Until this morning, I didn’t even know the post had appeared.

    I told him (and everyone) to be very careful when talking to reporters. They often take the most grandiose, wacky thing you say and quote it out of context to make their article more exciting. Something that makes sense in the midst of a longer conversation can make you look like an absolute idiot when taken by itself.

    Daniel Baumann does not believe that “There’s just no freedom in the laws of physics that we have.”

  32. Peter Woit says:

    John Baez,
    Thanks. This is odd though. In my experience Wolchover is one of the more careful science journalists around, and the problem here is not just the headline. Also in my experience, the reason bogus claims about fundamental theory get into popular articles is that theorists are all too willing to drop caveats and mix together their hopes for their work with what they actually have.

    Does Baumann also disavow the longer quote from the end of the article:

    “It’s “just aesthetically pleasing,” Baumann said, “that the laws are inevitable — that there is some inevitability of the laws of physics that can be summarized by a short handful of principles that then lead to building blocks that then build up the macroscopic world.”

    Other examples of this kind of misleading language can be found, see for instance the webpage for a recent Simons Foundation conference (Arkani-Hamed and Baumann two of the organizers)
    https://www.simonsfoundation.org/event/amplitudes-meet-cosmology-2019/
    which tells us
    “the laws of physics are a nearly inevitable consequence of quantum mechanics and special relativity. Nowhere is this seen more clearly than in the invariant observables associated with scattering amplitudes in asymptotically flat space.”
    You can find lots of Arkani-Hamed talks that very much seem to be saying that QM + special relativity inevitably give something like the Standard Model, as one random example, watch this IAS public talk:
    https://video.ias.edu/arkani-hamed-lecture-10-12

  33. JE says:

    Sorry, Peter, if this sounds presumptuous. Although I think you are making a good point and I very much agree with what you wrote re Quanta’s article, the whole discussion sounds a little bit over the top, especially after reading John’s comment above. IMHO, as other commenters have suggested, this article and the issues it raises with the title, subheading, etc. may just reflect the precarious state of HEP and the lack of good stories to write about in the HEP field.

  34. Peter Woit says:

    JE,
    One point of view on why HEP is in a precarious state would be because of the damage caused by 35 years of misleading hype. From that point of view, trying to stop more of it might not be over the top…

  35. John Baez says:

    Baumann didn’t explicitly “disavow” other quotes from his article, but I’m not in the business of extracting disavowals.

    I agree that Natalie Wolchover is one of the best physics reporters out there. I wouldn’t have bothered talking about this otherwise.

    My goal is not to rake anyone over the coals. But I did want to make a bit of a stink. I think it’s the duty of all scientists to push back against nonsense.

  36. Natalie Wolchover says:

    Hi Peter (and John and others),
    We’ve changed the wording of the subhead and another sentence in the blog post and added a correction note at the bottom explaining the changes.

    As for Daniel Baumann, first I’ll just say that he and other bootstrappers are careful and conservative; in fact that’s kind of their whole thing! From a journalistic point of view, the quote that has so bothered some of you is a great quote. It’s passionate and reveals his feeling of being highly constrained by the rules, a la Mel Gibson as William Wallace yelling “FREEDOM!” It’s an exaggerated statement to which it is indeed possible to say, “Well, technically, not NO freedom…” The article tries to explain some of these technicalities. I’ve apologized to Daniel for causing him some grief over the quote.

    Thanks for keeping us on our toes, thanks for the apology, and I apologize to you all as well for not vetting the display copy well enough.

    Natalie

  37. Daniel Baumann says:

    Dear Peter et al.,

    I have never commented on a blog before, but since my words seem to be misinterpreted, maybe it would be helpful if I clarify the context of my remarks.

    Natalie asked me to explain the following two papers:

    Benincasa and Cachazo (2008) https://arxiv.org/abs/0705.4305
    McGady and Rodina (2014) http://arxiv.org/abs/1311.2938

    I was happy to do so, since I like these papers a lot and was impressed that Natalie would attempt to describe such a complex subject. My short (popular) summary of the papers can be found here:
    https://www.dropbox.com/s/50tvt2odrlgwkgc/Quanta.pdf?dl=0

    As you can see, it is only about massless particles and long-range forces. Everything I said in the article is in that context. In fact, we spoke for a long time and it was mostly a technical discussion on the details of these papers.
    That locality and unitarity fixes the long-distance interactions of massless spin-1 and spin-2 particles to be those of YM theory and GR is a beautiful fact that I tried my best to explain.

    Best,
    Daniel

  38. Peter Woit says:

    Hi Natalie and Daniel,

    Thanks a lot for the clarifications, that’s great! I’ve added a note about this at the end of the posting.

    Peter

  39. Low Math, Meekly Interacting says:

    I think I’ve witnessed something remarkable and encouraging happening here, and I thank all involved for finding a constructive conclusion.

    Natalie: I generally am very happy with Quanta’s reporting on physics and mathematics, and consider your work to be a standout in the field of popular science reporting. Any disappointment comes from the fact that you and your colleagues have made it worth it to even care. I am grateful for that, and also wish to add my encouragement. Please do keep up the good work. A quick perusal of the “industry standard” of online pop-sci content make it clear how sorely it’s needed.

  40. DK says:

    Just a suggestion: For all the blog postings, perhaps the “Updates” can be added at the very top rather than at the bottom, appropriately delineated? Will improve readability.

  41. tulpoeid says:

    I am afraid I will act kind of like a party spoiler. I hesitated doing so but I keep thinking that the view of those who don’t enjoy Quanta magazine could be a useful addition here.

    So, being a physicist, a researcher, and a reader of popular science press, a few months into reading Quanta articles I had to firmly decide that I stop doing so (the couple of times I went back reaffirmed my decision). I find them too long and too imbalanced – they are trying to both water down the subject and speak to quasi-experts at the same time, missing the objective of having a clear target group. In the best cases, I couldn’t get any new knowledge on the promised topic because it is either buried in a deep and convoluted way or it wasn’t really there to begin with. This is probably a result of heavy editting and of very specific guidelines, and I say so because even Hossenfelder’s clear writing becomes Quanta-ized over there.

    In the worst cases, it is sheer propaganda. I realize that steps were taken thanks to this post and the discussion under it. But at the same time I wonder how good, or at least how objective, it is to congratulate Wolchover. As far as I can tell her articles have consistently been eulogies of fake physics for a few years now and in the end it will always be “I was only covering”. I don’t know whether she is one of the top science journalists right now, but I am almost sure that she has contributed to building the inaccurate picture that the public mistakes for proven physics facts lately.

    To wrap up, correcting one’s article is certainly commentable. But I can’t help thinking that it is an integral part of journalistic work. Again, I am aware that all this will probably sound a bit off, however the urge to bring into discussion the fact that not every HEPer looks up to Quanta has been surging in me for ten days now…

  42. Peter Woit says:

    tulpoeid,
    First of all, I think you need to compare what Quanta is doing to what other outlets for science journalism (such as Scientific American) are doing, and I think they come off very well in that comparison.
    Secondly, covering HEP theory has very special problems. The material is difficult for even experts to understand, and if journalists try and deal with this by consulting the most prominent people in the field, they have a thorny thicket of BS to try to find their way through. I don’t think you can blame the results on the journalists. As a point of comparison, consider Physics Today, which is the house organ of the US physics community. The main person over the years they have turned to for coverage of HEP BSM physics has been Gordon Kane (no less than three articles from him). So, it could be much worse…

  43. Severin Pappadeux says:

    My first read on spin-2 particle leading inevitably to general relativity was from Feynman Lectures on Gravitation, given at Caltech 1962

  44. Cosmin says:

    You are actually talking about a very old dilemma: who is to blame, the physicists or the editors/gatekeepers. Now everyone wants to be in the active physicists field (99%) but very few (read almost nobody – 1%) wants to do the editing/gatekeeping work, for various reasons. The result is that strânge ideas get a pass simply because nobody is there to stop them. Everyone wants to play but nobody wants to be the referee.

  45. Peter Woit says:

    Cosmin,

    The problem of gate-keeping/refereeing within the physics community is a different one than the problem here, which is that of gate-keeping between the public and theorists with an idea to promote. This is what journalists have to do, and in my experience they’re enthusiastic and willing to work hard at it to try and get it right. But, especially for highly technical theoretical work (a good example would be no-go theorems, where the issue of the significance of various technical assumptions is at the center of the problem) there’s no way they can evaluate the significance of the work themselves. They have to rely on the self-control of the theorists themselves, their willingness to be careful and not overstate their case, as well as the willingness of their colleagues to take them to task when they go too far.

  46. Sebastian Thaler says:

    Frank Wilczek on Twitter today: “It’s time to concede that this was not, alas, the decade of supersymmetry. Hope springs eternal, but the terms of bets are finite … I’ve got two to pay off.”

  47. Peter Woit says:

    Sebastian Thaler,

    I did see that, at
    https://twitter.com/FrankWilczek/status/1211973691644489728

    The remarkable thing about all those who have lost SUSY bets is that I’ve never seen any of them draw the conclusion that there is something wrong with the idea. Wilczek’s loss of a bet on SUSY leads him to conclude “this was not, alas, the decade of supersymmetry”, but that “hope springs eternal”.

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