Arkani-Hamed on Naturalness

For the latest SUSY enthusiast take on the implications of what the LHC has been (not) seeing, your best bet might be yesterday’s talk at the KITP by Nima Arkani-Hamed on Naturalness. An hour and 40 minutes, no slides, nothing much on the blackboard, just him talking about how he now sees things. Some high points:

  • If the Higgs turns out to have spin two, he’ll quit physics.
  • If the Higgs turns out to be a techni-dilaton, he’ll kill himself.
  • At this point, a natural theory would have to be rather baroque, so he favors abandoning naturalness in favor of simplicity.
  • The simplest thing is the Standard Model, but that requires too much fine-tuning. He won’t completely abandon naturalness: one part in a million fine-tuning is fine, but the SM fine-tuning problem isn’t. This is the point where he loses me (going from the SM to the vastly more complicated SUSY theories with the needed SUSY breaking seems to me not close to being worth the supposed improvement in the fine-tuning).
  • He complains that “Some BSM theorists are giving our field a bad name” by repeatedly making SUSY predictions that turn out to be wrong and changing their story.
  • He’s not one of those: he still favors split SUSY, and has since 2004.
  • Split SUSY makes a falsifiable prediction: no Higgs gamma-gamma excess. This is of course the same prediction as the Standard Model.
  • In his favored version of split SUSY, all SUSY partners are much too heavy to ever be observable except the wino, bino and gluino. He had a lot to say about what observing these would tell us, but not much about what the implications are of not seeing them in the LHC 8 TeV run. Would this just mean “surely they’ll show up at 13 TeV”? Is seeing nothing at 8 TeV consistent with split SUSY? What about seeing nothing at 13 TeV?

In any case, giving up on SUSY is definitely not on the agenda as far as he’s concerned.

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23 Responses to Arkani-Hamed on Naturalness

  1. BrianW says:

    Hmm, I thought much of the talk was merely politics. I’m not sure he really believes the old susy stuff anymore. At the end, he does consider the possibility that all these favoured susy ideas are ruled out for good, which sounds to me like he’s betting on a new top down twistor picture, but of course not willing to say so.

  2. lun says:

    :If the Higgs turns out to be a techni-dilaton, he’ll kill himself.

    Unlike _any_ scalar field theory, “technicolor” (Asymptotically free theories with a Gauge group) is known rigorously to be non-trivial and stable (in a Renormalization Group sense). What exactly is the problem?

  3. Hmunu says:

    Are these long rambling talks the norm for theoretical particle physics or is this specific to Arkani-Hamed? You have posted links to a few talks of his here and each time, I am amazed at the sophomoric quality of the presentation. I realize that the primary focus of a particle theorist isn’t to give PowerPoint presentations that would make a marketing firm jealous, but I feel like this talk suggests a lack of seriousness about communicating one’s ideas to the unconverted.

  4. MathPhys says:

    I think it was Feynman who said that one doesn’t need more than one argument if one has a single good argument.

    There is an element of using the audience as sounding boards in these talks. On the other hand, I’m sure people at KITP and elsewhere are more than happy to help him articulate his thoughts, no matter how long that takes.

  5. Mark says:

    Hi Peter,

    I wonder what you think people should work on if they give up on SUSY? What I wonder is if there is anything else that already hints at another way forward for BSM@TeV type scales (not including the usual things people work on like large extra dimensions, ZPrimes and so on – all of which of course have also not been observed so far) that we can look for at the LHC, or if SUSY is not there we really need some idea that has not been thought of at all (given most of the mainstream ideas I know of are also heavily constrained by LHC searches).

  6. not a fun of big names says:

    All Nima’s models are wrong, how dare he blames the rest of the BSM community??? Enlarging (the energy level) of new particles/predictions is the way of doing physics (of course one reason for this is we need to ask funding from government), think about the time before people discovered top quark. By the way, 10^-6 is UN-Naturalness, everyone knows that!

  7. chris says:

    “a natural theory would have to be rather baroque”

    i wonder how many people can truly appreciate the subtle irony of this sentence.

  8. JR says:

    Hmunu, Good questions. NAH seems to be one of few people who can ramble and still remain riveting! As for power point, I have never seen him use that, he makes nice carton drawings with a real actual felt pen! Makes me feel like I am back in 1985!. Somewhat refreshing really. Regarding talks with no prepared material, this is mostly the domain of the rich and famous, not recommended for job talk! Also it is not reserved for particle physics, Bob Laughlin used to give wonderful talks on condensed matter theory. He might scribble something like H*Psi=E*Psi on the board but that was it!


  9. Tienzen (Jeh-Tween) Gong says:

    Thanks for the link.
    I am a linguist. Thus, I will not comment on the physics. But, I can decode messages. Seemingly, Nima tried to convey two points in his 100 minutes long talk.
    a. He just delivered a great eulogy for his pet SUSY.
    b. He is making an announcement for joining the Technicolor camp.

  10. Eric says:

    Regarding naturalness, how do we know that supersymmetry doesn’t naturally solve a different hierarchy problem in a hidden sector, and electroweak symmetry breaking is simply a secondary effect ? From this perspective, there would be no naturalness problem as the electroweak scale would be only weakly correlated with the mass of the superpartners. However, there would be a different scale, perhaps associated with dark matter, which is strongly correlated with supersymmetry. Presumably this other scale would then somehow trigger EWSB. It really make no sense to be overly concerned with naturalness until we have a complete picture of all physics rather than just the small SM sector which makes up only 3% of the universe.

  11. tt says:

    a different problem in a hidden sector ?
    so its a solution looking for a problem ?

  12. Eric says:


    No, that is not what I am saying. Supersymmetry still provides the explanation for why the Higgs mass is light and thus solves the hierarchy problem. My point is that the scale of the superpartners does not have to necessarily be strongly correlated with the electroweak scale as there could be lots of other physics happening that is not apparent at the present time. So what may appear to require a small amount of fine-tuning, the so-called little hierarchy problem, may appear completely natural when the full picture is in view.

  13. Bernhard says:


    “Lots of other physics” (whatever that is) could also show SUSY is unnecessary and by itself solve all problems, including the hierarchy problem, wouldn’t you agree? Not that I want to discuss about nothing, but if the game is to claim some vague undiscovered physics to rescue SUSY one my well take a shortcut and use it to solve whatever problems the Standard Model might have.

  14. Bernhard says:

    sorry, *might well take*

  15. Hmunu says:

    @ JR – As a graduate student born in the mid 1980s, talks with transparencies conjure up professors giving the same physics lectures that they gave when first granted tenure in the 70s. And I have never found a rambling technical talk riveting, even in my own sub-field, because all I end up thinking is “get to the point!” I wasn’t saying that this issue is exclusive to particle theorists, but I am always amazed that high profile people in this field just fly by the seat of their pants when giving a talk.

    I sort of understand the appeal of nostalgia, but I must wonder if Professor Arkani-Hamed would find this type of talk acceptable by one of his graduate students. If the answer is yes, then that explains many other theory talks I have read and witnessed that lack a coherent structure. They just have been taught that this presentation style is right way to give a talk. That is pathetic and sad.

    @ MathPhys – While presentations during workshops will naturally have less structure then an APS plenary, usually they aren’t this free-form. Trying to start a discussion doesn’t mean you don’t prepare slides to keep the discussion on track. If someone needs assistance to work out the details of a model, do it with colleagues while relaxing on the beach or in the local pub. Maybe I just don’t like theory talks that amount to “My Thoughts About the Universe.”

  16. Peter Woit says:


    This was a weird and unusual format for a talk. Then again, he’s in a pretty weird and unusual situation right now: he just got a $3 million check for ideas that don’t work and that are in the middle of getting clobbered by experiment. So, he’s got some explaining to do…

  17. Tienzen (Jeh-Tween) Gong says:

    American President seldom use slides for his policy arguments. There is no need of using slides for some important announcement. Nima’s Susy was well-known, and he was not trying to promote it anymore. His points were very clear, no slide is needed.
    a. Although we can arbitrary push the susy scale to 1000 Tev or higher, it (susy) always has a “tail” trapped at or below one Tev region. That is, no tail at LHC, no susy.
    b. If the LHC data shows b or c (which are now the hints in the data), then not only is Nima’s pet a goner but also are all its variants.
    c. Seemingly, Nima did not like Technicolor before. But, in this talk, he mentioned that the techni-type solutions rescued physics three times in the past. He also admitted that Technicolor “should” be correct although … . He mentioned Technicolor almost 10 times in this talk.

    Nima is the first one openly announcing the beginning of the end of a long susy era (over 40 years long). I congratulate him.

  18. rrtucci says:

    This reminds me of the film “The Caine Mutiny”

  19. Jim Akerlund says:

    I just saw the video and at the 88 minute mark a women in the audience is reading “Not Even Wrong” on her computer. The camera operator seems to be trying to show this by the long screen time spent with her computer centered. I recognized your page by the “First Results from the Large Hardon Collider” picture she has on the computer.

  20. Chris Oakley says:

    Yes – I am sure that if they had spelled “hadron” correctly, it would not have attracted all this prurient interest.

  21. Peter Woit says:


    Yes, took a look and that’s definitely NEW she’s paying attention to, not Nima. Very funny…

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  23. plm says:

    Jim and Peter:
    It would have been funny if you had put an embedded link to the video and the woman had been seeing herself on NEW seeing herself on NEW seeing herself on NEW… in real time. She could have eventually discerned “Not Even Wrong” written with composite Higgs in a tiny video.

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