Unification, Spinors, Twistors, String Theory

Last month I recorded a podcast with Curt Jaimungal for his Theories of Everything site, and it’s now available with audio here, on Youtube here. There are quite a few other programs on the site well worth watching.

Much of the discussion in this program is about the general ideas I’m trying to pursue about spinors, twistors and unification. For more about the details of these, see arXiv preprints here and here, as well as blog entries here.

About the state of string theory, that’s a topic I find more and more disturbing, with little new though to say about it. It’s been dead now for a long time and most of the scientific community and the public at large are now aware of this. The ongoing publicity campaign from some of the most respected figures in theoretical physics to deny reality and claim that all is well with string theory is what is disturbing. Just in the last week or so, you can watch Cumrun Vafa and Brian Greene promoting string theory on Brian Keating’s channel, with Vafa explaining how string theory computes the mass of the electron. At the World Science Festival site there’s Juan Maldacena, with an upcoming program featuring Greene, Strominger, Vafa and Witten.

On Twitter, there’s now stringking42069, who is producing a torrent of well-informed cutting invective about what is going on in the string theory research community, supposedly from a true believer. It’s unclear whether this is a parody account trying to discredit string theory, or an extreme example of how far gone some string theorists now are.

To all those celebrating Thanksgiving tomorrow, may your travel problems be minimal and your get-togethers with friends and family a pleasure.

Update: If you don’t want to listen to the whole thing and don’t want to hear about spinors and twistors, Curt Jaimungal has put up a shorter clip where we discuss among other things the lack of any significant public technical debate between string theory skeptics and optimists. He offers his site as a venue. Is there anyone who continues to work on string theory and is optimistic about its prospects willing to participate?

Posted in Euclidean Twistor Unification, Uncategorized | 17 Comments

Spacetime is Right-handed v. 2.0 and Some Notes on Spinors and Twistors

I’ve just replaced the old version of my draft “spacetime is right-handed” paper (discussed here) with a new, hopefully improved version. If it is improved, thanks are due to a couple people who sent helpful comments on the older version, sometimes making clear that I wasn’t getting across at all the main idea. To further clarify what I’m claiming, here I’ll try and write out an informal explanation of what I see as the relevant fundamental issues about four-dimensional geometry, which appear even for $\mathbf R^4$, before one starts thinking about manifolds.

Spinors, twistors and complex spacetime

In complex spacetime $\mathbf C^4$ the story of spinors and twistors is quite simple and straightforward. Spinors are more fundamental than vectors: one can write the space $\mathbf C^4$ of vectors as the tensor product of two $\mathbf C^2$ spaces of spinors. Very special to four dimensions is that the (double cover of) the complex rotation group $Spin(4,\mathbf C)$ breaks up as the product
$$Spin(4,\mathbf C)=SL(2,\mathbf C)\times SL(2,\mathbf C)$$
where these two factors act on the spinor spaces.

While spinors are the irreducible objects for understanding complex four-dimensional rotations, twistors are the irreducible objects for understanding complex four-dimensional conformal transformations. Twistor space $T$ is a $\mathbf C^4$, with complex conformal transformations acting by the defining $SL(4,\mathbf C)$ action. A complex spacetime point is a $\mathbf C^2\subset T$ and conformally compactified complex spacetime is the Grassmannian of all such $\mathbf C^2\subset T=\mathbf C^4$. One of the spinor spaces at each point of complex spacetime is tautologically defined: it’s the point $\mathbf C^2$ itself (the other is of a different nature, with one definition the quotient space $T/\mathbf C^2$).

Real forms

While the twistor/spinor story for complex spacetime is quite simple, the story of real spacetime is much more complicated. When several different real spaces complexify to the same complex space, these are called “real forms” of the space. A real form can be characterized by a conjugation map $\sigma$ (an antilinear map on the complex space satisfying $\sigma^2=1$), with the real space the conjugation-invariant points. Using the obvious conjugation on $\mathbf C^4$, we get an easy to understand real form: the $\mathbf R^4$ with real coordinates, rotation group $SL(2,\mathbf R)\times SL(2,\mathbf R)$ and conformal group $SL(4,\mathbf R)$. Unfortunately, this real form seems to have nothing to do with physics, its invariant inner product is indefinite of signature $(2,2)$.

The real spacetime with Euclidean signature inner product has an unusual conjugation that is best understood using quaternions. If one picks an identification of the twistor space $T$ as $T=\mathbf C^4=\mathbf H^2$, then the conjugation is multiplication by the quaternion $\mathbf j$. The Euclidean conformal group is the group $SL(2,\mathbf H)$. The spinor spaces $\mathbf C^2$ are identified with two copies of the quaternions $\mathbf H$, with the rotation group now the group $Sp(1)\times Sp(1)$ of pairs of unit quaternions.

In this case the conjugation acts in a subtle manner. Since $\mathbf j^2$ is $-1$ rather than $1$, it’s not a conjugation on $T$, but is one on the projective space $PT=\mathbf CP^3$. It has no fixed points, so the twistor space has no real points. What is fixed are the quaternionic lines $\mathbf H\subset \mathbf H^2$, each of which corresponds to a point in the (conformally compacified, so $S^4=\mathbf HP^1$) real Euclidean signature spacetime. Using the decomposition as a tensor product of spinors, the action by $\mathbf j$ squares to $-1$ on each factor, but $1$ on the tensor product, where it gives a conjugation with fixed points the Euclidean spacetime.

The real spacetime with Minkowski signature is another real form of a subtle sort, with very different subtleties than in the Euclidean case. The conjugation $\sigma$ in this case doesn’t take the twistor space $T$ to itself, but takes $T$ to its dual space $T^*$. It takes spinors of one kind to spinors of the opposite kind (at the same time conjugating spinor coordinates to get anti-linearity). The Minkowski signature conformal group is the group $SU(2,2)$ and the rotation group is the Lorentz group $SL(2,\mathbf C)$ (acting diagonally on the two spinor spaces, with a conjugation on one side).

Some philosophy

The usual way in which the above real forms get used is that mathematicians ignore the Minkowski story and use the Euclidean signature real form to do four-dimensional Riemannian geometry, with the $Sp(1)\times Sp(1)$ decomposition at the Lie algebra level corresponding to the decomposition of two-forms into self-dual and anti-self-dual. Physicists on the other hand (especially Penrose and his school, but also those trying to do quantum gravity using Ashtekar variables) ignore the Euclidean story and use the Minkowski signature real form. In various places Penrose is quoted as explicitly skeptical of any relevance of the Euclidean story to physics. Working just with the Minkowski real form, one struggles with the fact that the Lorentz group is simple, but that one can get a very useful self/anti-self dual decomposition if one makes one’s variables complex.

The point of view I’m taking is that Wick rotation tells one that one should look simultaneously at both Euclidean and Minkowski real forms, understanding how to get back and forth between them. This is standard in usual geometry where one just looks at vectors, but looking at spinors and twistors shows that something much more subtle is going on. The argument of this new paper is that when one does this, one finds that the spacetime degrees of freedom can be expressed purely in terms of one kind of spinor (right-handed by convention), the one that twistor theory tautologically associates to each point in spacetime. The other (left-handed) half of the spinor geometry involves a purely internal symmetry from the point of view of Minkowski spacetime. This should correspond to the electroweak gauge theory, exactly how that works is still under investigation…

Update: Now posted on the arXiv here. Only reaction on social media I’ve seen so far is from Strinking42069, which seems to be a parody account trying to make fun of string theorists.

Posted in Euclidean Twistor Unification | 18 Comments

Analytic Stacks

Dustin Clausen and Peter Scholze are giving a course together this fall on Analytic Stacks, with Clausen lecturing at the IHES, Scholze from Bonn. Here’s the syllabus:

The purpose of this course is to propose new foundations for analytic geometry. The topics covered are as follows:
1. Light condensed abelian groups.
2. Analytic rings.
3. Analytic stacks.
4. Examples.

Yesterday Clausen gave the first lecture (video here), explaining that the goal was to provide new foundations, encompassing several distinct possibilities currently in use (complex analytic spaces, locally analytic manifolds, rigid analytic geometry/adic spaces, Berkovich spaces). These new foundations in particular should work equally well for archimedean and non-archimedean geometry and hopefully will be the right language for bringing together the Fargues-Scholze geometrization of local Langlands at non-archimedean places with a new geometrization at the archimedean place. He describes as “(very) speculative” the possibility of a geometrization of global Langlands (with Scholze more optimistic about this than he is).

Tomorrow Scholze will take over, giving the next six lectures. Perhaps this characterization is a bit over-the-top, but seeing lectures of this sort and of this ambition taking place at the IHES brings to mind the glory days of Grothendieck’s years lecturing at the IHES on new foundations for algebraic geometry. I fear that keeping up on the details of this as it happens will require the energy of someone much younger than I am…

Update: Scholze’s first lecture is here. He gives his version of the motivation for these new foundations.

: This sort of thing didn’t happen back in the days of SGA.

Posted in Langlands | 13 Comments

Spacetime is Right-handed

I’ve finally managed to write up something short about an idea I’ve been working on for the last few months, so now have a preliminary draft version of a paper tentatively entitled Spacetime is Right-handed. One motivation for this is the problem of how to Wick rotate spinor fields, given that Minkowski and Euclidean spacetime spinors are quite different. In particular, it has always been a mystery why a Weyl spinor field has a simple description in Minkowski spacetime, but no such description in Euclidean spacetime, where the Euclidean version of Lorentz symmetry seems to require introducing fields of opposite chirality. The argument of this paper is that the relation between Euclidean and Minkowski is not the usual chirally-symmetric analytic continuation but something where both sides use just one chirality (“right-handed”). It’s quite remarkable that the dynamics of gauge fields and of GR also has a chiral-asymmetric formulation.

In the ideas about unification using QFT formulated in Euclidean twistor space that I’ve been working on the past few years, it was always unclear why, when you analytically continued back to Minkowski signature, the left-handed Euclidean spin symmetry would not go to the Lorentz boost symmetry, but to an internal symmetry. One goal of this paper is to answer that question.

This past weekend I recorded a podcast with Curt Jaimungal, which presumably will at some point appear on his Theories of Everything site. It includes some discussion of the ideas behind the new paper.

Posted in Euclidean Twistor Unification | 17 Comments

Frenkel on String Theory

Curt Jaimungal’s Theories of Everything podcast has a new episode featuring a long talk with Edward Frenkel (by the way, I’ll be doing one of these next month). A few months ago I wrote about a Lex Fridman podcast with Frenkel here. While both of these are long, they’re very much worth watching.

While there’s some overlap between the two podcasts, some different topics are covered in the new one. In particular, one thing that happened to Frenkel since last spring is that he attended Strings 2023 and gave a talk there (slides here, video here). The experience opened his eyes to just how bad some of the long-standing problems with string theory have gotten, and starting around here in the podcast he has a lot to say about them.

It’s pretty clear that his reaction to what he saw going on at the conference was colored by his experience growing up in late Soviet-era Russia, where the failure of the system had become clear to everyone, but you weren’t supposed to say anything about this. He pins responsibility for this situation on senior leaders of the field, who have been unwilling to admit failure. As part of this, he acknowledges his own role in the past, in which he was often happy to get some reflected glory from string theory hype by playing up its positive influence on parts of mathematics while ignoring its failure as a theory of the real world. In any case, I urge you to watch the entire podcast, it’s well worth the time.

For a very different perspective on the responsibility of senior people for string theory’s problems, you might want to take a look at the bizarre twitter feed of stringking42069, which may or may not be some very high-quality trolling. In between replies and tweets devoted to weightlifting, weed and women, the author has some very detailed and mostly scornful commentary on the state of the field and the behavior of its leaders. His point of view is that the leaders have betrayed the true believers like himself, abandoning work on the subject in favor of irrelevancies like “it from qubit”, in the process tanking the careers of young people still trying to work on actual string theory. For a summary of the way he sees things, see here and here. Comments on specific people here and here.

This weekend here in New York if you’ve got $35 you can attend an event bringing together five of the people most responsible for the current situation. I doubt that the promised evaluation of “a mathematically elegant description that some have called a “theory of everything.”” will accurately reflect the state of the subject, but perhaps some of the speakers will have listened to what Edward Frenkel has to say (or read stringking42069’s tweets) and realized that a new approach to the subject is needed.

Update: Curt Jaimungal at the Theories of Everything podcast has a new episode, discussing quantum gravity with Jonathan Oppenheim. Around 1:10 Oppenheim has some comments about the current problem of few opportunities for young people to pursue new ideas in this field, including:

You know, it’s a multifaceted problem. I think part of it is that for whatever reason, people like to work on the same thing as everyone else. And I mean, we are social creatures, and we want to be part of the community. And so if there’s a big community doing something, then it’s very natural to want to be part of that community and do that research.

But it’s, I feel like it’s gotten to quite an extreme. It feels quite extreme at the moment, I feel like even when I was a student, you know, there were various researchers who, I would say, didn’t have a firm allegiance to say, string theory or loop quantum gravity, and you could kind of work with one of them and work on your own approach. Whereas I think now, for whatever reason, the landscape has just become a lot more divided into different communities who do different things, and it’s much harder to go off on your own. And maybe that’s just because it’s students’ worry that if they go off on their own, they won’t get a job. I think that’s probably a big part of it.

Update: Bringing together this and the last posting, if you’d like more Frenkel and more Langlands, there’s a new Numberphile video out.

Posted in Uncategorized | 30 Comments

What Does Spec Z Look Like?

This week Laurent Fargues has started a series of lectures here at Columbia on Some new geometric structures in the Langlands program. Videos are available here, but unfortunately there is a problem with the camera in that room, making the blackboard illegible (maybe we can get it fixed…). Fargues however is writing up detailed lecture notes, available here, so you can follow along with those.

Fargues is covering the story of the Fargues-Fontaine curve and the relationship between geometric Langlands on this curve and arithmetic local Langlands that he worked out with Scholze recently. On Monday Scholze gave a survey talk in Bonn entitled What Does Spec Z Look Like?, video available here. Scholze’s talk gave a speculative picture of how to think about the global arithmetic story, with Spec Z as a sort of three-dimensional space. One thing new to me was his picture of the real place as a puncture, with boundary the twistor projective line. He then went on to motivate the course he will be teaching this fall with Dustin Clausen on Analytic Stacks. Here at Columbia we have an ongoing seminar on some of the background for this, run by Juan Rodriguez Camargo and John Morgan.

Update: Peter Scholze next week at the Rapoport conference will be giving a talk on new ideas about the twistor $$\mathbf{P}^1$ and real local Langlands. His abstract is

Towards a formulation of the real local Langlands correspondence as geometric Langlands on the twistor-$\mathbf P^1$

We will propose a formulation of the local Langlands correspondence for complex representations of real groups in terms of a(n everywhere unramified) geometric Langlands correspondence on the twistor-$\mathbf P^1$, analogous to our work with Fargues in the case of p-adic groups. This is motivated by discussions with Rodriguez Camargo, Pan, le Bras and Anschütz on the analogous case of locally analytic p-adic representations, and is different from the previous work of Ben-Zvi and Nadler in a similar direction. In particular, on the geometric side we get representations of the real group, encoded in terms of liquid quasicoherent sheaves on $[*/G(\mathbf R)^{la} ]$; and on the spectral side, we get representations of the real Weil group $W_R$, or rather vector bundles on $[(\mathbf A^2\backslash\{0\})/W_R^{la} ]$.

Posted in Langlands | 24 Comments

Various and Sundry

The math department at Columbia this fall will be hosting three special lecture series, each with some connection to physics (at least in my mind…):

Some other less inspirational topics:

  • The news this summer from the LHC has not been good. On July 17 a tree fell on two high-voltage power lines, causing beams to dump, magnets to quench, and damage (a helium leak) to occur in the cryogenics for an inner triplet magnet. See here for more details. Fixing this required warming up a sector of the ring, with the later cooldown a slow process. According to this status report today at the EPS-HEP2023 conference in Hamburg, there will be an ion run in October, but the proton run is now over for the year, with integrated luminosity only 31.4 inverse fb (target for the year was 75).
  • The Mochizuki/IUT/abc saga continues, with Mochizuki today putting out a Brief Report on the Current Situation Surrounding Inter-universal Teichmuller Theory (IUT). The main point of the new document seems to be to accuse those who have criticized his claimed proof of abc of being in “very serious violation” of the Code of Practice of the European Mathematical Society. This is based upon a bizarre application of the language

    Mathematicians should not make public claims of potential new theorems or the resolution of particular mathematical problems unless they are able to provide full details in a timely manner.

    to the claim by Scholze and Stix that there is no valid proof of the crucial Corollary 3.12. It would seem to me that Mochizuki is the one in danger of being in violation of this language (he has not produced a convincing proof of this corollary), not Scholze or Stix. The burden of proof is on the person claiming a new theorem, not on experts pointing to a place where the claimed proof is unsatisfactory. Scholze in particular has provided detailed arguments here, here and here. Mochizuki has responded with a 156 page document which basically argues that Scholze doesn’t understand a simple issue of elementary logic.

    Also released by Mochizuki today are copies of emails (here and here) he sent last year to Jakob Stix demanding that he publicly withdraw the Scholze-Stix manuscript explaining the problem with Mochizuki’s proof. Reading through these emails, it’s not surprising that they got no response. The mathematical content includes a long section explaining to Scholze and Stix that the argument they don’t accept is just like the standard construction of the projective line by gluing two copies of the affine line. On the topic of why he has not been able to convince experts of the proof of Corollary 3.12, Mochizuki claims that he convinced Emmanuel Lepage and that

    one (very) senior, high-ranking member of the European mathematical community has asserted categorically (in a personal oral communication) that neither he nor his colleagues take such assertions (of a mathematical gap in IUT) seriously!

    I suppose this might be Ivan Fesenko, but who knows.

  • Since the Covid pandemic started, the World Science Festival has not been running its usual big annual event here in New York. This fall they will have an in-person event, consisting of four days of discussions moderated by Brian Greene. In particular there will be a panel Unifying Nature’s Laws: The State of String Theory evaluating the state of string theory, featuring four of the most vigorous proponents of the theory (Gross, Strominger, Vafa and Witten). I suspect their evaluation may be rather different than that of the majority of the theoretical physics community.

Update: Quanta has a very good article by Kevin Hartnett about the telescope conjecture in homotopy theory and its recent disproof. This is due to work of Ishan Levy, Robert Burklund, Jeremy Hahn and Tomer Schlank, all of whom gave talks on the subject at the Oxford conference this past June in honor of the 65th birthday of Mike Hopkins. Videos of the talks are available here. If homotopy theory is not your thing, and if you haven’t heard Graeme Segal speak recently about his thinking on the definition of quantum field theory, you could instead watch his talk.

: Video of Klainerman’s lectures will be available here:

Posted in abc Conjecture, Uncategorized | 13 Comments

The Philosophy of Supersymmetry

A few months back I saw a call for papers for a volume on “Establishing the philosophy of supersymmetry”. For a while I was thinking of writing something, since the general topic of supersymmetry is a complex and interesting one, about which there is a lot to say. Recently though it became clear to me that I should be writing up other more important things I’ve been working on. Also, taking a look back at the dozen or so pages I wrote about this 20 years or so ago for the book Not Even Wrong, there’s very little I would change (and I’ve written far too much since 2004 about this on the blog). What follows though are a few thoughts about what “supersymmetry” looks like now, maybe of interest to philosophers and others, maybe not…

First the good: “symmetry” is an absolutely central concept in quantum theory, in the mathematical form of Lie algebras and their representations. Most generally, “supersymmetry” means extending this to super Lie algebras and their representations, and there are wonderful examples of this structure. A central one for representation theory involves thinking of the Dirac operator as a supercharge: by extending a Lie algebra to a super Lie algebra, Casimirs have square roots, bringing in a whole new level of structure to familiar problems. In physics this is the phenomenon of Hamiltonians having square roots when you add fermionic variables, providing a “square root” of infinitesimal time translation.

Going from just a time dimension to more space-time dimensions, one finds supersymmetric quantum field theories with truly remarkable properties of deep mathematical significance. Example include 2d supersymmetric sigma models and mirror symmetry, 4d N=2 super Yang-Mills and four manifold invariants, 4d N=4 super Yang-Mills and geometric Langlands.

But then there’s the bad and the ugly: attempts to extend the Standard Model to a larger supersymmetric model. From the perspective of 2023, the story of this is one of increasingly pathological science. In 1971 Golfand and Likhtman first published an extension of the Poincaré Lie algebra to a super Lie algebra. This was pretty much ignored until the end of 1973 when Wess and Zumino rediscovered this from a different point of view and it became a hot topic among theorists. Very quickly it became clear what the problem was: the new generators one was adding took all known particle states to particle states with quantum numbers not corresponding to anything known. In other words, this supersymmetry acts trivially on known physics, telling you nothing new. It became commonplace to advertise supersymmetry as relating particles with different spin, without mentioning that no pairs of known particles were related this way. In all cases, a known particle was getting related to an unknown particle. Worse, for unbroken supersymmetry the unknown particle was of the same mass as the known one, something that doesn’t happen so the idea is falsified. One can try and save it by looking for a dynamical mechanism for spontaneous supersymmetry breaking and using this to push superpartners up to unobservable masses, but this typically makes an already pretty ugly theory far more so.

The seriousness of this problem was clear by the mid-late 1970s, when I was a student. The one hope was that maybe some extended supergravity theory with lots of extra degrees of freedom would dynamically break supersymmetry at a high scale, leaving the Standard Model as the low energy part of the spectrum. There wasn’t any convincing way to make this work, and it became clear that one couldn’t get chiral interactions like those of the electroweak theory this way. 1984 saw the advent of a different high scale model supposed to do this (superstring theory), but that’s another story.

Looking back from our present perspective, it’s very hard to understand why anyone saw supersymmetric extensions of the SM as plausible physics models that would be vindicated by observations at colliders. For example, Gross and Witten in 1996 published an article in the Wall Street Journal explaining that “There is a high probability that supersymmetry, if it plays the role physicists suspect, will be confirmed in the next decade.” Ten years later, when the Tevatron and LEP had seen nothing, the same argument was being made for the LHC. After over a decade of conclusive negative results from the LHC, one continues to hear prominent theorists assuring us that this is still the best idea out there and large conferences devoted to the topic. Long ago this became pathological science. In the call for papers, the issue is framed as:

recent debates on the prospects of low energy supersymmetry in light of its non-discovery at the LHC raise interesting epistemological questions.

From what I can see, the questions raised are not of an epistemological nature, but perhaps the philosophers will find a way to sort this out.

Update: There was a workshop on this last year, abstracts here.

Update: I happened to come across today this 2021 interview of Daniel Freedman by David Zierler. Zierler repeatedly asks Freedman why he has faith in SUSY despite the long history of no evidence. Near the end, Freedman gives this very defensive explanation:


What I hear in your remarks is an adherence to supersymmetry despite its immediate experimental prospects. Is that a belief or is it something more?


It’s a belief which stems from confidence in the powerful symmetry which underlies the subject. Some human beings indulge in beliefs which have no basis whatsoever. Some of those beliefs are destroying our society at the moment. My belief in a credible and interesting physical theory isn’t going to hurt anybody.

Posted in Uncategorized | 23 Comments

Strings 2023

For much of the past week, I’ve been attending off and on (on Zoom) the Strings 2023 conference. This year it’s in a hybrid format, with 200 participants in person at the Perimeter Institute, and another 1200 or so on Zoom. These yearly conferences give a good idea of what some of the most influential string theorists think is currently important, and I’ve been writing about them for twenty years. Videos of the talks are being posted here.

As in many of these Strings conferences in recent years, there was very little discussion of strings at Strings 2023. Of the 24 standard research talks, only 4 appeared to have anything to do with strings. A new innovation this year was to schedule in addition four “challenge talks”, conceived of as talks explicitly about material outside of string theory that might interest string theorists. In particular Edward Frenkel gave a nice survey of a wide range of ideas from quantum integrable systems and ending up with geometric Langlands. He motivated this with reference to what Feynman was working on very late in life and the problem of solving QCD. His slides are here, video here.

In addition there were four morning “Discussion Sessions”, which I attended most of, and at which string theory put in little to no appearance. Today’s discussion featured Nati Seiberg and Anton Kapustin and was about lattice versions of QFT, especially in their topological and geometrical aspects, a very non-stringy topic dear to my heart. Yesterday was It From Qubit, which had Geoff Penington discussing topics related to black holes. The conventional wisdom now seems to be that the information paradox is gone, solved semi-classically, so giving no insight into true quantum gravity dynamics. While this means you can’t see anything interesting at large distances from the black hole, Penington had some new ideas about something that might in principle be observable at atomic-scale distances from a super-massive black hole. Maldacena started off the session with slides promoting the way forward as quantum computer simulations involving 7000 qubits, a variant on the wormhole publicity stunt. The only time string theory made an appearance was in a suggestion by Dan Harlow that perhaps by doing quantum computer simulations theorists could solve the the problem of what “string theory” really is. It’s pretty clear what the leading direction is now for continuing the long tradition in string theory of outrageous hype.

After this week, I’m even more mystified about why the conference was called “Strings 2023” And how does one decide these days what “string theory” is and who is a “string theorist”? Oddly, two of the things that now distinguish this yearly conference from others are a pretty rigid exclusion of both real world physics (Frenkel comments on this here) as well as of what got people excited about string theory, superstring unification and its implications for seeing low energy SUSY at colliders. People still interested in that have split off to other conferences, especially String Phenomenology 2023 and SUSY 2023.
Those conference have their own kinds of mysteries (why do people keep working on ideas that failed long ago?). In particular, the closing talk on the Status and Future of Supersymmetry at SUSY 2023 was all about the great prospects for SUSY at the LHC, and included a Conclusion written (no joke) by ChatGPT:

The future of supersymmetry as a research program holds both exciting challenges and potential breakthroughs. While the LHC experiments have yet to observe direct evidence of supersymmetric particles, ongoing theoretical advancements and refined experimental techniques offer renewed hope. The future of supersymmetry research lies in two key directions. Firstly, novel theoretical models are being explored, including new variants of supersymmetry that incorporate dark matter candidates or non-linear realizations. These approaches push the boundaries of our understanding and allow for further exploration of the particle zoo. Secondly, upcoming experiments, such as the High-Luminosity LHC and future colliders, aim to explore higher energy scales and increase the sensitivity to supersymmetric signals. With these advancements, the quest for supersymmetry will continue to shape the field of particle physics, inspiring new theoretical insights and propelling experimental discoveries.

Things just get stranger and stranger…

Update: Speaking of stranger and stranger, you can listen here to Sean Carroll talking by himself for four hours and twenty-two minutes about why there really is no crisis in physics, the whole supersymmetry/string theory thing is going just fine.

Update: I hadn’t realized just how accurate Joe Conlon’s description of the conference as “IAS-centric” was. For the four discussion sections, no IAS in one of them (“strings, QFT and mathematics”, the other 3 sessions were all IAS (two IAS faculty, the rest an assortment of ex or current members).

Posted in Strings 2XXX | 18 Comments

This Week’s Hype

Nanopoulos and co-authors have predictions from superstring theory that are “in strong agreement with NANOGrav data.” He has been at this now for almost 40 years. See for instance Experimental Predictions from the Superstring from 1985, where the superstring predicted a top mass of 55 GeV and 360 GeV squarks.

Posted in This Week's Hype | 11 Comments