2008 Physics Nobel Prize

Half of this year’s Nobel Prize in physics has been awarded to Yoichiro Nambu for his work on spontaneous symmetry breaking, the other half to Kobayashi and Maskawa for the CKM matrix as an explanation of CP breaking. A detailed explanation of the scientific context of the prizes is here.

The prize for Nambu is well-deserved and rewards one of the deepest, surprising, and most important ideas in particle theory, that of spontaneous symmetry breaking. In 1960 Nambu realized that non-invariance of the vacuum state under an axial symmetry could explain the existence of pions and determine many of their properties. He also realized that this phenomenon is closely related to what happens in various condensed matter models (including the BCS model of superconductivity), where the ground state is not invariant under a symmetry of the theory. Nambu has often been mentioned as a candidate for the award, and it’s surprising that it has taken nearly 50 years for it to come about. I’m a bit curious about how often Nobel Prizes in other fields are awarded for work done a half-century ago. Unfortunately the rather difficult times particle physics has found itself in the last few decades may mean that the best way for a particle theorist to get the prize is to have been around during the field’s heyday, and to remain in good health.

The Kobayashi-Maskawa award is a somewhat less obvious one, since it didn’t involve a surprising breakthrough, and it is about something completely different than Nambu’s work. In the early-mid 60s, starting with work by Nicola Cabibbo, it had been shown that (in modern language…) flavor mixing matrix for two generation models of the weak interactions is governed by a single angle, now known as the Cabibbo angle. In 1972, Kobayashi and Maskawa pointed out that for three generations the matrix is determined by three angles and a complex phase. The complex phase makes this a possible source of CP violation, and it seems to be the main if not only source of observed CP violation. The Nobel committee text makes the claim that:

This is in fact a result known in mathematics since around 1950, but the contacts between mathematics and physics were not great around 1970.

This is a rather odd description of the situation, since the mathematical facts involved here are quite simple ones about which 3×3 unitary matrices satisfy certain conditions, and presumably could have been derived by mathematicians who first worked with such matrices in the 19th century if this particular condition had come up. I can’t think of anything mathematicians learned around 1950 that is needed to solve the problem, and, once stated physicists could easily solve it without help from mathematicians (who perhaps would have been more likely to just have been a hindrance in this case…)

The quark mixing matrix embodies most of the unknown parameters of the Standard Model, and as such is a crucial object for experimental studies of particle physics. Because of this, the KM paper is the second most highly cited paper in particle physics (after Weinberg’s “A Model of Leptons”), but this ranking doesn’t reflect the depth or importance of the ideas.

Lots of other blogs are also covering this. Tommaso Dorigo points out that it’s a bit anomalous that a Nobel Prize for the CKM (Cabibbo-Kobayashi-Maskawa) matrix doesn’t include Cabibbo, who is still around. Lubos Motl thinks that what is important here is that Nambu is also a string theorist, and that one of the people on the committee making this choice was a string theorist, Lars Brink.

Update: Lots of coverage of this in the press. Michio Kaku has an editorial in Forbes, where, like Lubos, he sees the real significance as being that Nambu is a string theorist:

And there may even be a theory beyond the Standard Model, a true theory of everything that can unify all forces. It’s called string theory.

Not surprisingly, one of the founders of string theory is Professor Nambu, a newly minted Nobel Laureate who has years of research ahead of him. The best is yet to come.

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32 Responses to 2008 Physics Nobel Prize

  1. Warren says:

    it’s surprising that it has taken nearly 50 years for it to come about. I’m a bit curious about how often Nobel Prizes in other fields are awarded for work done a half-century ago.

    van Vleck

  2. Peter Woit says:

    Thanks Warren,

    That’s also physics, but it’s true it was awarded at a time (1977) when particle physics was a lot healthier, and there were a lot of recent advances that could have been awarded prizes.

    I was a student at Harvard at the time, and from what I remember, the conventional department celebration was a bit impeded by the fact that van Vleck was long retired and gone, I heard rumors that no one even knew how to locate him and contact him….

  3. Pablo says:

    On his blog Lubos says: “Nambu, a Japanese-born American, is often described as one of the “fathers of string theory . . But the Nobel prize is formally given to him for a comparably famous discovery “, which implies that the REAL reason for the Nobel is not that discovery, BUT his work on string theory . . . interesting lecture of the events.

  4. helvio says:

    I don’t agree with your opinion that the work of Kobayashi and Maskawa (KM) is not a breakthrough. As I see it, their suggestion was: 3 families => CP-violating phase => matter/antimatter asymmetry. Only 2 families were known by then, so adding a 3rd family is for me a very bold working hypothesis, albeit a very simple one. And this is because its consequences are not only physically relevant but also philosophically profound. I put this breakthrough in par with the proposal of strangeness (2nd family) to explain the pattern of particles in the 60’s. It was also a very simple working hypothesis, but which makes a lot of sense theoretically when you see its consequences, and it fits the data when you later test it.

  5. Peter Woit says:


    Sorry, I agree that postulating a strange quark (2nd generation) may have been a bold hypothesis, but once you have two generations, postulating a third just doesn’t seem that bold.

  6. JC says:

    Didn’t Chandrasekhar get his Nobel Prize (in 1983) for work he did in the 1930’s?

  7. helvio says:

    What I mean is that the boldness is not just in the hypothesis, which is pretty easy to make, but in suggesting it and showing explicitly that it leads to a profound conclusion, like CP-violation. The mathematics of 3×3 matrices is very simple, indeed, but it’s the chain of arguments in their paper that matter, and the insight of recognizing that it’s a very important discovery and not a triviality. Even though Lorenz wrote down his transformations, it was Einstein who established the logical sequence of arguments that make them a consequence of a small number of very basic but profound principles. Even though ‘t Hooft claims to be the first to have calculated the beta function of QCD, he thought it was a triviality; but for Gross, Wilczek, Politzer it wasn’t trivial, they recognized its physical relevance. Every first-year grad student is able to do the same calculation, it’s a simple one, but the real physics is in the interpretation, and that even the best can miss. Kobayashi and Maskawa interpreted rightly the relevant physics behind such a simple hypothesis, that’s why I think they fully deserve the prize!

  8. Steve Myers says:

    Isn’t the problem for Cabibbo is that they won’t give the prize to 4? Same with Dyson.

  9. I absolutely agree – while a couple of colleagues are suspicious of a particle physics prize in an area that seems obscure to them, given the year that’s in it (LHC), I think the prize for Nambu is well-deserved and decades overdue (compare with Saalam and Glashow for example).

  10. P.S.
    I mean I absolutely agree with the post above, not the comments. That said, I too think it’s most unfair that the third musketeer of the CKM mechanism was left out – that damn rule

  11. JC says:

    By a similar argument, should Ludwig Faddeev have received the 1999 Nobel Prize (with ‘t Hooft and Veltman) in analogy with Cabibbo vs. K + M ?

  12. spear mark says:

    Well, the value of KM is related to the value you place on getting a better handle on why we are made of matter, and not some sort of thin gruel of photons, electrons, and positrons that would have resulted if matter and antimatter were completely symmetric.

    Cronin and Fitch got the price in 1980 or so for the experimental discovery of CP violation, and it is very appropriate that KM get a piece of the prize for the phenomenology that most closely describes the experimental result. Their phenomenology led to more experimental work… the Fermilab and CERN experiments on direct CP violation and the Babar/Belle experiments. That pretty much proved that KM were right, and so the timing of the prize to them is just about right.

    Of course, from a theoretical perspective, KM’s math is trivial and so their work is not so impressive. But in contrast to string theory, KM’s work is closely tied to the physical world, which in some people’s mind is more important than impressive mathematics.

    Cabibbo’s work, I thought, was not easy to separate from other similar contributions, although he got the name on the parameter.

    To me the surprise was Nambu. I’m sure he’s a great guy, but there have already been prizes to Glashow, Weinberg, Salam, t’Hooft, and Veltman for similar work. Actually, there are way too many prizes to theorists for the Standard Model, and too few to experimentalists.

    How about Prescott for polarized electron scattering? Or a group for 3 jet events? The long b lifetime? Unfortunately, in the current climate, there is a theology that nothing happened in experimental particle physics since 1974 or so. That is merely theology, however. The actual experimental work of the last 35 years is crucial and innovative, just undervalued.

  13. A says:

    The “Nobel prize that Kobayashi-Maskawa will get within 3 years” was announced in a my comment on NEW 2 years ago, see href=”http://www.math.columbia.edu/~woit/wordpress/?p=465#comment-16690.

    The reason why Cabibbo is excluded is that two-generation mixing was already mentioned in a footnote in an earlier paper by other authors (unfortunately I forgot which paper).

  14. Meow says:

    Clicking on the Motl link displays a Woit-bashing page

  15. cyd says:

    Weird. Why were Goldstone and Cabibo left out? If it’s due to the only-three-per-year rule, surely they can give it to, say, Nambu and Goldstone this year, and to Cabibo, Kobayashi, and Maskawa next year.

  16. cyd says:

    > I’m a bit curious about how often Nobel Prizes in other fields are awarded for work done a half-century ago.

    Abrikosov and Ginzburg finally received their prizes only in 2003, for the profound work they did in the 1950s.

    Incidentally, the 2003 prize would have been Landau’s second Nobel prize—Ginzburg’s prize was for the Ginzburg-Landau theory—if the committee had been a little more timely, and if he had live longer. As it turned out, Landau had his famous and tragic car accident 1962; the Prize was quickly given to him in that year, for his work on superfluidity, for fear that he would die without being honored.

  17. Coin says:

    Isn’t the problem for Cabibbo is that they won’t give the prize to 4? Same with Dyson.

    I’m told that this was also a problem in medicine this year, with the Nobel Prize going to two members of the team that discovered HIV causes AIDS, and also the guy who discovered HPV causes cervical cancer; with some third guy who ran a separate team with a claim to have codiscovered HIV being left out. It’s not entirely clear whether this choice was actually a determination that the third guy’s claim to HIV priority was illegitimate, or whether they just ran out of slots.

  18. An italian says:


  19. dir says:

    the point of km’s work is cp violation mechanism, they predicted the third generation fermions. this work is very important, but also a kind of easy, and km themselves are not comparable with nambu who is really great.

    as for the work of quark mixing, not only cabibbo, gell-mann and levy had a similar work in 1960, their paper should be the following one, nuovo cimento 16 (1960) 705.

  20. Anonymous says:

    Increasingly these days I’m more and more skeptical of the Nobel prize’s worth… I mean, if you do phenomenal work why shouldn’t you be recognized for it (i.e. case of Cabibo)? what exactly does a (rule on) limitation on number of recipients have anything to do with the scientific value of the research?

    And furthermore, the Nobel Committee seems to think the universe of academic research – perhaps less so literary – revolves around their validation… does it actually?! The Committee/s awarding the prizes have had a (seemingly unending) streak of pompousness on how they perceive themselves as ‘judges of value’ when they assign credit / value to other people’s research.

    Bottom line: A number of their decisions over the years haven’t been as objective as one would hope to believe for so prestigious a prize; and some of their awards have been based on factor/s not directly associated with strictly intellectual / academic merit.

    (I won’t mention specific cases because would start a controversy which I don’t particularly want to get into).

  21. anonymous fool says:

    The most rescent Bulletin of the AMS contains an interview with Atle Selberg, in which he comments about prizes.


    Here are some excerpts:

    “Question. You have received the Fields Medal in 1950. You also have received the
    Wolf Prize in 1986. Three years ago the Abel Prize in mathematics was established. What are your thoughts on these types of prizes in general—do you think they have a positive effect?
    It does not advance science. No one does scientific work because there exist
    prizes—I cannot imagine that. A prize will make one or more persons happy, but
    it also gives rise to disappointment among many people, I would imagine.
    Question. But do you believe it serves mathematics in the sense that it creates
    publicity and thus raises the awareness of the public?
    Whether it serves mathematics to get publicity is an open question.
    Question. Coming back to the Abel Prize: what are your thoughts on the awards
    so far?
    I proposed Serre and Grothendieck as candidates for the first award in 2003, as
    some people I would have preferred. I thought that Serre would get it, and that
    also happened. Since then I have not made any proposals. Concerning the Abel
    Prize, I have a somewhat ambivalent attitude. Let us consider the Nobel Prize:
    I think it has caused some unintended harm by creating a strong distinction inprestige between those that get the prize and others, who certainly deserve it, but do not get it. There are, of course, some people that so clearly outshine others that the award is uncontroversial; in physics, for example, you have Einstein, Bohr,Heisenberg, Dirac, and a few others. However, since the prize is awarded yearly, it is inevitable that the distinction will not be so clear. . .”

  22. Thomas Larsson says:


    – When it comes to figuring out who made seminal medical discoveries, we in the Nobel committee are the world experts, not a bunch of laywers, says Bertil Fredholm, chairman of the Nobel committee at the Karolinska institute.

  23. DB says:

    “It’s not entirely clear whether this choice was actually a determination that the third guy’s claim to HIV priority was illegitimate, or whether they just ran out of slots.”

    You’re referring to Robert Gallo whose role in the discovery of the Aids virus was long the subject of major controversy. Anyway, not a very good day for Italians (Cabibbo) or Americans of Italian descent (Gallo).

  24. Christine says:

    At least two Brazilians physicists also “missed” receiving the Nobel prize:

    -Mario Norberto Baibich in 2007 for the Giant Magnetoresistance effect, see here (he was the first author of the paper describing the effect).

    -César Lattes: although he was the main researcher and the first author of the Nature paper on the meson pi, Cecil Powell was awarded the Nobel for it in 1950; see here.

    According to an interview with Lattes:

    Question: Do you think that the fact of being Brazilian contributed so that another researcher gained the Physics Nobel in the research where you have participated?

    CL: Although the judge commission was formed by Englishmen, I believe that it was not my nationality that weighted in the decision of the winner. As much in the discovery of pion, in 1946, as in its artificial creation, in 1948, I had the contribution of the Giuseppe Occhialini. He was the one who should have received the prize. And, in 1950, who took the prize was the Cecil Powell, who also participated in the work. But forget about this. These huge prizes do not help science.

  25. Shantanu says:

    BTW this is the first time IIRC, that the names of the nobel committee
    (at least in Physics) has been made public. Is that right? (or in previous years also the committee has been public?)

  26. Pankaj says:

    One could perhaps argue that KM deserved Nobel prize more than Nambu. KM showed how CP-violation could be explained. They gave a theoretical
    idea for an experimental fact. This idea could have been proposed by some else, but they were the first. This happens quite often in science. Even the experimental discovery of CP-violation could have been done by someone else. Their case is more like Glashow whose ideas have experimental support; while perhaps there is no experimental support for the ideas of Weinberg and Salam for which they got the Nobel Pize. Nambu’s case might be more like Weinberg and Salam. However, it is also true that Nambu, Weinberg and Salam are held in higher regard generally for their multifaceted contribution to physics and perhaps because their contributions have been more mathematical. But in the end,
    what may count is the discovery of the
    secrets of nature rather than how
    mathematically inclined your work is.

  27. Thomas Larsson says:

    Shantanu, the members of the Nobel committees have AFAIK always been public. That would be difficult to keep secret, given that the committee members can attend the Nobel ceremony and banquet, with TV survey and everything. However, the protocols from the committee meetings are kept secret for at least 50 years, so you have to wait to see who voted for whom.

  28. MathPhys says:

    So why not J Goldstone precisely? I thought it was always known as the Nambu-Goldstone mechanism. Maybe Goldstone didn’t publish?

  29. Shantanu says:

    Thanks, Thomas. Do you or anyone else knows why S.N. Bose (of Bose-Einstein statistics ) was not awarded the Nobel prize and if
    he was voted ? (as I presume he would have been shortlisted more than
    50 years ago that the protocols must have been made public)

  30. Thomas Larsson says:

    I don’t know specifically about Bose, but an interesting account of the politics surrounding the early Nobel prizes for QM can be found here.

  31. Travis says:

    Just a nit to pick a few days late:

    From SPIRES current citation counts, KM is the 3rd most cited paper in HEP, after Weinberg and then Maldacena. And of course the PDG’s Review of Particle Physics dwarfs everyone with well over 20,000 to all versions.

    I suppose this error is my fault, since we haven’t posted new all time lists recently, and the “pass” happened recently. However, note that you can, for the most part, do this yourself live:

    Find topcite 3000+ and sequence by citation count [SPIRES]

    Which will give you _current_ papers over 3000 citations in order.

    Mind you, this has nothing to do with the Nobel. Clearly the order of these papers, and the exact number of citations at this point, is more of a reflection of the community than saying anything too important about the papers. This high on the list there are, I hope, better ways of assessing the impact of a paper [this is probably true in general, but that’s another story…].

  32. MathPhys says:

    There is some serious science fiction in the 3000+ list.

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