50 Years of Electroweak Unification

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

The latest CERN Courier has (from Frank Close) a detailed history of the paper and how it came about. It also contains a long interview with Weinberg. It’s interesting to compare his comments about the current state of HEP with the ones from 2011 (see here), where he predicted that “If all they discover is the Higgs boson and it has the properties we expect, then No, I would say that the theorists are going to be very glum.”

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

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

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

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

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

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

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16 Responses to 50 Years of Electroweak Unification

  1. Low Math, Meekly Interacting says:

    Weinberg must be aware of his great fortune: He was alive during a period when his theories about fundamental physics could be subjected to rigorous empirical challenge, and either survive or not. I am lucky to have been alive to see “the” Higgs boson discovered. To have been born later may mean to have been born after the end of that era of fundamental discovery.

  2. Art says:

    From Close’s article: 1) “QED is perhaps the simplest example of a general class of “non-abelian gauge theories””. Um, QED is abelian, right? 2) “it shows how it is easier to be Beethoven or Shakespeare than to be Steven Weinberg”. Quite a stupid statement, no?

  3. vmarko says:

    I am a bit surprised by the article of Frank Close. It’s all about Weinberg, mentioning only in passing that Glashow and Salam&Ward had figured out the SU(2)xU(1) symmetry no less than eight years earlier, in 1959. What Weinberg actually did in the 1967 paper was to combine this with the Higgs mechanism in order to break the symmetry spontaneously. And yes, Weinberg does quote one of the Glashow papers (in a slightly dismissive tone), so at least he did know about it, and most probably read it.

    I don’t want to put off Weinberg’s contribution to EW model, but I think Close doesn’t do justice to Glashow and Salam, let alone Ward.

    Best, 🙂

  4. Benson Woo says:

    It was wonderful to read Frank Close’s account of the history of Weinberg’s paper, especially the epiphany Weinberg had while driving his red Camaro to MIT. What if he had been doing something different that Sept 1967 day? These behind the scenes stories of how discoveries get made happen all the time.

  5. physicsphile says:

    Very nice articles. I was surprised to read that Weinberg works with the TV on! I would find that too distracting.

  6. Frog Leg says:

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

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

    I apologize if you’ve covered this before, but how do you think would graduate training be different from today?

  7. Peter Woit says:

    Frog Leg,

    This really is a different and large topic, better for another time, but some obvious ideas are:

    1. the parts of the usual graduate training that traditionally have been devoted to getting students up to speed on the most “advanced” topics (in HEP theory: e.g. GUTS, SUSY extensions of the SM, superstring theory) should be deemphasized, in favor or explaining what problems those ran into, why they haven’t worked.

    2. instead of rushing through the fundamentals of basic tools like QFT, it might be a good idea to devote more time to those and give students a better chance to become familiar with the trickier parts of those fundamentals. This is more likely to make it possible for someone approaching the subject with a fresh perspective to possibly come up with a new and successful fundamental idea.

  8. David Derbes says:


    The CERN Courier article is an edited excerpt from Close’s The Infinity Puzzle. The article focused on Weinberg, but the book doesn’t. Salam, Ward, Glashow, Schwinger and many others (specifically ‘t Hooft and Veltman, and Higgs, Englert, Brout, Guralnik, Hagen and Kibble) are mentioned and receive large credit at various places in the book for work on the electroweak theory. You or I might weigh credit differently from Close, but nothing he wrote struck me as unfair while I was reading the book.

  9. Ilyas says:

    @vmarko and @David Derbes

    David, you make a good point about Close’s book (the source of the excerpt). There is a view that Close is somewhat negative about Salam in the context of the way in which he (Salam) was the third person that the Nobel committee chose. I dont know if you have seen the Noorman Dombey article ( https://arxiv.org/pdf/1109.1972.pdf ) but it is an interesting additional part of that little side-story around electroweak unification and who should (or should not) be credited. There are a few nice pieces written on the overall topic, but regardless of the negativity around Salam I like Close’s book. Its really well written, and it does not cut corners in trying to be “popular”.

  10. Peter Woit says:

    Ilyas and others,
    The Dombey article was discussed extensively here back in 2011
    and the Close book a couple months later:

  11. a reader says:

    Steven Weinberg is a true giant, but his closing remarks, that “the actual work is so, well…it’s so chillingly non-human. I need to feel that I am still part of the human race while I’m doing it,” were a bit of an anticlimax. As Ulysses says in Dante’s Inferno, “considerate la vostra semenza: fatti non foste a viver come bruti ma per seguir virtute e canoscenza.” Rather than being “chillingly non-human,” physicists’ actual work is eminently human, and it is something our species can be proud of.

  12. piscator says:

    a reader: I took exactly the opposite message. Given how technically algebraically oppressive Weinberg’s textbooks are (I know how good he is, but the style just doesn’t work for me) I find more than slightly amusing the fact that they may have been written to a backdrop of old films or cheap TV.

  13. David Brown says:

    In the livestream “Reminiscences of the Standard Model” by Weinberg, he made an interesting comment (around 1:18:15 in the YouTube video) concerning the work of string theorists, “… they haven’t settled down to any particular theory, and we don’t know whether that works anyway. I hope it does.”

  14. Lucimário Custódio says:

    Yesterday Steven Weinberg gave a online lecture, “The Rise of the Standard Models”, invited by the brazilian physics society. Here’s the youtube link:


  15. paddy says:

    Despite his personality, I found (as a student 40+ years ago) Weinberg’s didactic “algebraic” approach informative. Mathematical and example driven texts are helpful for those of us who are not geniuses.

  16. Fiona says:

    Peter, maybe this preprint https://arxiv.org/abs/1710.06149 is of interest and worth a comment? They propose the “conformal standard model”, an extension of the standard model up to Planck scale without susy and without loops.

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