Experimentalists 1, Theorists 0

At Fermilab the Tevatron is producing record amounts of luminosity, see here for a story about a celebration of this. Things also appear to be going well at the LHC, as the cooldown remains on schedule, and only a tolerable number (12) of PIMs needed to be replaced in the sector recently warmed back up. See here and here for some discussion of current planning for the next year. The machine should be cool and ready for beam commissioning in late June, and if all goes well, by September an initial physics run with 5 TeV beams at relatively low luminosity may begin. At these luminosities and energies, the stored energy in the LHC beam will be no greater than at the Tevatron (although the important number for physics, the per-particle collision energy, will be 5 times higher). The plan is to run until December, with a heavy-ion run at the end, then shutdown until April 2009. During the shutdown the magnets will be trained, allowing beams at the full energy of 7 TeV during the 2009 run.

Particle theory, especially string theory, is not doing as well. Data recently compiled about top-cited particle physics papers from 2007 shows only one [note added: should specify string theory here, at 27 and 31 are phenomenology papers from 2002 and 2000] theory paper from this century making the list of 51 most heavily cited papers, and that was the KKLT paper which is referenced by all “landscape” and “multiverse” studies. The sad state of string theory has even made it deep into the popular consciousness. Last week’s episode of “The Big Bang” featured a brilliant young prodigy explaining to the particle theorist character that his work on string theory was a “dead-end”, due to the landscape problem. Even economists are dissing the subject:

Modern financial theory as applied ranks with string theory in physics as one of the greatest intellectual frauds of our time. Whereas the vacuous pretensions of string theory have finally been exposed (we now know that the theory never generated a single falsifiable prediction), those of “financial engineering” are just beginning to be exposed both in the press and in lawsuits alike.

At Santa Barbara, Jennifer Ouellette reports on a workshop about “how to come off better during TV appearances”:

Joe Polchinski (inventor of D branes in string theory, and one of the few permanent members at KITP) also agreed to be mock-interviewed, revealing a sly sense of humor in the process. For instance, asked if there was any controversy about string theory, he deadpanned, “Oh no. Everybody agrees that string theory is correct.” It cracked up the room.

This workshop unfortunately didn’t seem to include the advice to just say no when asked by TV producers to participate in a short stupid comedy skit making fun of science and scientists. See here, here and here, for reports on Wednesday’s “Root of All Evil” show from Comedy Central, which featured a mercifully short segment making fun of scientists as incomprehensible geeks. Participating in things like this does about as much to help the image of science and scientists as appearing on a Spike TV segment about the use of physics to determine whether women can crush beer cans with their breasts.

Given that things are going very well with the LHC, and badly with string theory, string theorists are doing the logical thing: advertising their activities with graphics of strings superimposed on a picture of the LHC. See here and here.

Update: Minutes from the LHC Installation and Commissioning Committee April 11 meeting are here. They include the exchange:

L.Evans asked if the cryogenics teams are still on track for having the whole machine at operating temperature in mid-June. S.Claudet replied that taking the figure of 6 weeks from room temperature to 2K, and allowing 2 weeks of cryo tuning, sector 45 would be ready for hardware commissioning in the first half of July.

This indicates that beam commissioning is likely to begin in July, not June.

Also discussed was what to do about possible stray plastic parts in the beam tube:

Any pieces of plastic would be vaporised by the beam so we should not delay start-up to search for these.

Update: Commentary on this posting from Lubos here, including

I am amazed by the people who deliberately keep on opening the pile of manure called Not Even Wrong – it must be due to a really nasty deviation of theirs that dwarves pedophilia.

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140 Responses to Experimentalists 1, Theorists 0

  1. oohay says:

    Summary of the black hole discussion:
    [1] There are very good reasons to believe that the evaporation of a black hole in AdS is a unitary process.
    [2] Exactly how this happens is not understood, but work proceeds.
    [3] We have no clue as to whether the evaporation of a realistic black hole is unitary. All we can say is [a] well, realistic black holes are still *black holes*, and if some black holes evaporate in a unitary way, well, maybe they all do, and [right out on the lunatic fringe now] [b] after all, AdS with small curvature is not so different from de Sitter spacetime; I mean, apart from the different causal structure, the fact that one has a timelike Killing vector and the other does not, and that they have totally different topologies, they are almost the same thing. Just drop the anti. *Therefore* the evaporation of a real black hole must be unitary, right? At least in certain extremely boosted Reference Frames.

  2. woit says:


    Sure, there may be QFT theories of quantum gravity that are just as untestable or unpredictive as string theory. The reason so many physicists got interested in string theory was that it is supposed to explain something observable: particle physics. It is as a unified theory of particle physics that string theory has turned out to be a failure. It is the claims people are making comparing this failed theory of particle physics to the successful QFT approach that are ludicrous sophistry.

  3. Vince Velocci says:

    I’m not sure if this comment is relevant to this discussion, but I will submit it anyway. I’m not really surprised that a proposed unified theory of particle physics and gravity (string theory) isn’t a UNIQUE theory of particle physics, allowing us to derive the masses of particles and the couplings of forces. I mean, why should we believe that a mathematical theory will logically and necessarily imply our universe and all its gory details? It makes sense that this theory can describe many many universes because I don’t see why our universe is a logical necessity, following from some mathematical theory us humans have cooked up. I don’t think pure mathematics will ever lead, uniquely, to our universe. Things have to be put in. Plus, I don’t think our minds our perfect, so whatever kind of model we cook up will always be an approximation to the truth and only observation will enable us to come up with better and better models. But just as our minds are imperfect, so will our models be.
    Maybe I don’t really understand things all too well, but I just don’t see how mathematics can uniquely imply our universe with all its constants.

  4. Eric says:

    “It is the claims people are making this failed theory of particle physics to the successful QFT approach that are ludicrous sophistry.”

    It seems to me that QFT and string theory are actually two sides of the same coin, and are essentially equivalent. Is this not what Ads/CFT teaches us? QFT and string theory are essentially dual descriptions.

    The bottom line is that one can easily construct QFT’s from string theory, so what goes for one also goes from the other. The only thing lacking at present is the particular construction from string theory which gives us the QFT that we observe, the standard model.

  5. Peter Woit says:


    Again, the problem with string theory is not that it can’t predict things uniquely. It’s that it can’t predict anything at all.


    According to your argument, the weakly coupled electroweak theory is a string theory since AdS/CFT says it is dual to strongly coupled string theory. But what is strongly coupled string theory? Well, the only answer to that is to apply AdS/CFT again and you have just shown that weakly coupled QFT is weakly coupled QFT…

  6. Eric says:

    “Again, the problem with string theory is not that it can’t predict things uniquely. It’s that it can’t predict anything at all.”

    One only needs to find the particular string vacuum which describes our universe in detail. Once one has such a construction in hand, and all moduli are stabilized, then one can predict the values of all couplings, such as gauge couplings and Yukawa couplings. Also, it should also be possible to address the issue of supersymmetry breaking within such a construction, and describe any new physics.

    In regards to cosmology, string theory can essentially make a predicton in regards to inflation: no tensor modes.

  7. woit says:


    You’re not keeping up with the latest string cosmology research. See for instance


    where Silverstein and Westphal discuss string cosmology models with observable tensor modes.

    “One only needs to find the particular string vacuum which describes our universe in detail”

    You’re ignoring the minor problem that you don’t know how to calculate in detail the predictions of realistic string vacua, and that there are 10500 of these calculations you don’t know how to do…

  8. Eric says:

    Yes, I’m aware of the Silverstein-Westphal paper. However, this paper is still a little controversial.

    “You’re ignoring the minor problem that you don’t know how to calculate in detail the predictions of realistic string vacua, and that there are 10^500 of these calculations you don’t know how to do..”

    Actually, we do know how to calculate in detail many predictions for a wide class of vacua. This is where the moduli stabilization issue comes into play. As I stated earlier, once this is done, all quantities such as the Kaeler potential and gauge kinetic function can be uniquely calculated. What is still needed is an example of a fully realistic example. Finding such an example might be closer than you realize. To be honest, your knowledge on this is about 20 years out of date.

  9. Peter Woit says:


    Instead of just insulting me as ignorant, please provide me with a reference to a paper which gives a string theory background with fully stabilized moduli and a reliable calculation of Yukawa and gauge couplings, accurate enough to be compared to experiment. One of the easiest things to compute in such a background should be ground state energy, so tell me what the result of that calculation is.

  10. Eric says:

    At present, there are several examples of semi-realistic vacua in the literature where many of these calculations can be performed, which I encourage you to study. As I stated previously, a particular vacuum where it can be claimed to be fully realistic has yet to be found. However, there has been a lot of progress and I don’t think that it will be too long before this happens.

    I should emphasize that the problem is not in calculating couplings. The issue is in finding a particular vacuum which 1) has exactly a three-generation standard model in its low-energy limit and nothing else, 2) satisfies all consistency conditions, 3) all Yukawa couplings are allowed by selection rules, and 4) all moduli may be stabilized, so that the values of all couplings may be calculated. The problem is that perhaps 3 out of 4 of these conditions may be satisfied for a particular construction, but so far not all.

  11. Peter Woit says:


    I’ve looked at many papers of the kind you describe. From what I’ve seen, generically the kind of constructions you describe have vacuum energies that are wrong by a hundred orders of magnitude or more, and no hope of calculating Yukawas in a reliable manner that could be compared to experiment. If you claim otherwise, give a reference, not just over-hyped claims about what can be done, when it really can’t.

  12. piscator says:

    Peter, seriously, if your complaint is really that there is no remotely plausible way of constructing vacua which looks like the Standard Model and where the vacuum energy can be computed to agree with experiment, then it’s not just string theory you’re giving up on but particle theory in its entirety. No-one knows a good solution to the cc problem. The only halfway reasonable `solution’ is anthropica, and that approach (what a climbdown from the high points of particle theory) is nothing to boast about.

  13. Peter Woit says:


    My point is just that the CC is the easiest thing to compute in these vacua, and as far as I can tell, you can’t even calculate that in such a way that you could compare it to experiment. The state of the art seems to be that people are trying to see whether or not they can find an argument that would show existence in principle of a vacuum with small enough CC, even though it couldn’t actually be constructed.

    As for the rest of the continuous parameters of the standard model, e.g. Yukawas, every paper I’ve looked at seems to involve some kind of extremely crude approximation or other, with no reliable calculation of these numbers. I’d really like to get a reference from Eric or anyone else to a reliable calculation of Yukawas in a fully-stabilized string vacuum. People talk as if such things exist, but I haven’t seen such a thing.

    Seriously, I’d like to see references to somewhere such a calculation is done, or at least to somewhere which explains in detail what is needed to do such a calculation, e.g. what technical or conceptual problems still need to be solved before it is possible.

  14. dan says:

    Thanks for the reference, PW,

    quick question — If SUSY is broken at TEV scale, thus stabilizing the EW, and providing a solution to the hierarchy problem, should the Tevatron, with its luminosity and intensity, have the energy to see some of the lighter SUSY-partners/higgs?

  15. Peter Woit says:


    Many people expected evidence for supersymmetry to show up at the Tevatron if it really was at low enough energy to solve the hierarchy problem. The fact that this hasn’t happened is one piece of evidence against supersymmetry. As far as I know, the increases to come in Tevatron luminosity won’t change much the bounds on superpartners, progress on this will have to come from the LHC.

  16. Ethan Siegel says:

    Funny thing; Lubos came to my site a week or two ago and left a comment there when I commented on yours. I have analytic software installed, which tells me where he came from.

    And it was your site. Funny, but I think he might be one of your number one readers!

  17. woit says:


    I’m well aware that Lubos is one of my most loyal and attentive readers. Very often after I write about something here, a long denunciatory post about the issue at hand appears frighteningly quickly at his blog. It’s scary how fast the guy can write huge long postings. One example is the latest one about Connes, which, while containing lots of nonsense, does contain some material worth reading, largely because Lubos is writing about something he actually has some experience of, growing up under the Soviet system as implemented in Eastern Europe.

  18. piscator says:

    Hi Peter,

    Well, I think the cc can be computed quite easily in all the moduli stabilised backgrounds, it just that it tends to be at the natural scale you would expect based on supergravity, which depending on how you break supersymmetry is somewhere between (1 TeV)^4 and (10^7 TeV)^4. And effective field theory suggests that this is the answer you expect whatever high scale theory you are working with, as the Standard Model is valid up to a scale of a TeV. So either you need something very new and very smart, or you run away to anthropica and rely on a massive and uncalculable cancellation.

    As for Yukawas: a full calculation would require knowledge of the Kahler metrics for the matter fields. This is non-holomorphic, and therefore in general very hard to compute. Fully explicit formulae exist on tori, so how to compute Yukawas is in principle something that people know how to do, but there is (IMO) no background where you have controlled moduli stabilisation and a Standard Model sector, so it’s not clear comparing Yukawas with experiment is where progress lies right now.

  19. Peter Woit says:


    Thanks, that’s very helpful. From what I understand, except on tori you don’t have explicit Calabi-Yau metrics, would need to get them numerically and this is very challenging. Can you get fully-stabilized moduli on a torus or do you need some other Calabi-Yau?

  20. piscator says:

    Hi Peter,

    You may be able to get fully stabilised moduli on a torus, but I don’t know of any schemes there that really look plausible for breaking supersymmetry at a hierarchically low scale. Straight flux models with no non-perturbative effects may be able to stabilise everything on a torus, but then there is no obvious small parameter and the flux stabilisation will likely give you a gravitino mass (and thus susy breaking) around the GUT scale or so.

    On a Calabi-Yau, it may be possible to be fully explicit for local models, such as branes at singularities or resolutions thereof. Metrics are in some cases known there, and at the orbifold limit the string can be quantised. That said, I do not believe that full string calculations for the Kahler metrics have been carried out there, but it may be possible.

    For traditional vanilla global compactifications, such as the E_8 x E_8 heterotic string on a Calabi-Yau, then I would have expected that computing the full expression for the Kahler metric of chiral matter fields would be of the same order of difficulty as computing the Calabi-Yau metric itself.

    The superpotential is of course more tractable, and so some progress can be made purely through selection rules – if a Yukawa vanishes, it still vanishes whatever the normalisation is. Likewise if there are gauge symmetries and Froggatt-Nielsen type attempts at flavour are possible, assuming that all normalisation terms are O(1).

  21. Peter Woit says:

    Thanks again piscator, that’s very helpful. I’ve periodically tried to understand a bit about what the problems are in these kinds of calculations, your summary made the situation much clearer.

  22. dan says:

    Dear PW,

    Sticking back to the topic ‘My understanding is that the easiest thing to see is colored superpartners, since they are strongly interacting, and if these exist within the LHC reach, they should be found quickly, even in data from the hoped-for 2008 first physics run.”

    so by the end of this year, 2008, around Nov election time, if there are colored superpartners (superpartners of colored quarks I take it?) the LHC could see evidence of SUSY (which string theorists would take as proof of the correctness of String’s foundation)

    Anything else in the first hoped for 2008 run?

  23. Peter Woit says:


    Even if something like colored superpartners are there in the 2008 data, it may take quite a while for the experiments to properly analyze this data, and have enough confidence that they are seeing something like this to make an announcement.

  24. Dan says:

    Okay, thanks. When you write “and if these exist within the LHC reach, they should be found quickly” is there any reason to suspect that if SUSY does stablize EW scale, the LHC does not have enough energy to produce such strongly interacting colored susy-partners?

    If you don’t believe in SUSY as the explanation for hierarchy (and neither, presumably, does Eva Silverstein, with other string theorists offering LHC-accessible SUSy a 50-50%), how do you (they) propose the EW-higgs is stabilized? curious

  25. David B. says:

    Dear Dan:

    Alternatyive B to a technically natural explanation of the hierarchy problem is that the EW scale is stabilized because it is finely tuned. This means, no real explantion.
    This is a possibility that can not be discarded, although there is quite a bit of theoretical prejudice against it.

    Various people have used landscape-based arguments to say that this is indeed the case, because in the landscape sense, fine tunings can be accidental environmental parameters.

    This will be settled one way or another by the LHC, as it is the first machine that has been built that can reach and explore the EW symmetry breaking scale.

  26. milkshake says:

    I was reading the Lubos rant about Connes and even the part when he supposedly “knows what he is writting about” is full of it, as always, when he explained why soviet physics was not affected.

    Turns out Soviet physic was very nearly wiped out and replaced by “research on ether” the same way the biology and was replaced by teachings of Lysenko. There was actually a congress organised by soviet acad sci establishment, in 1946 I think, to purge soviet science of burgeois theories like relativity and uncertainity, and to put the young generation in line with the Party line on science – all scripted out, all denunciations prepared in advance – and it was called off just few weeks before it was when it became clear this would interfere with soviet bomb effort. “We can always shoot them later” was the Stalins comment on his decision to call it off.

  27. dan says:

    Thanks Dave B.

    I take it we’re looking 2010 at the earliest then for LHC to provide the requisite data & analysis?

  28. innocentbystander says:


    I wish I could share your optimism regarding general predictions
    from string theory. You mention two general
    predictions: 4d SUSY (which you tacitly
    assume in describing the problem in terms of a Kahler potential)
    and absence of tensor modes. Please indicate
    how you would establish either of these predictions.
    Finding *a* vacuum with the right properties obviously
    is not sufficient, since there may be many more
    which match current data but differ in other ways.
    And as Peter said, on tensor modes there is now a class
    of inflation models, which is at least as concrete as any
    other known class, in which a specific
    chaotic inflation type potential and prediction of of tensor modes drops out. How can you possibly exclude this possibility on general grounds?

  29. Eric says:

    Dear Innocentbystander,
    First, 4D supersymmetry may be established by the detection of superpartners at LHC. Second, finding a vacuum which reproduces the SM plus new physics that is later observed would establish the model.

    Examples of new physics might include the superpartner spectrum and extra matter which may arise from a hidden sector. Once a fully realistic model is constructed, the issue of supersymmetry breaking should be able to be addressed and it should be possible to calculate the soft-terms and therefore the low-energy superpartner spectrum.

    As far as your question regarding the uniqueness of such a vacuum, nobody knows at this point. At present, there is not even one such model which can be claimed to be fully realistic, so the claim that there will be multiple vacua which reproduce the SM in detail is

    Regarding the tensor modes, all I can say is that the paper which Peter referred to is currently being studied. It has not yet been accepted as valid. Many people who work on this topic are presently trying to find a problem with it, which is how the scientific process works.

  30. innocentbystander says:

    Dear Eric,

    Sure, what you say makes sense, and applies
    to all string cosmology models. As such, at
    present there
    is not a general prediction from theory regarding tensor modes.
    (This would be the case even
    if there were not a candidate mechanism for
    tensor modes in the literature.)
    Different mechanisms make different predictions, and
    those which appear in advance of the next round of
    observations in fact provide cosmological
    examples along the lines you suggest for
    particle physics (that is, examples of models
    which are currently viable, and can be observationally tested in
    the foreseeable future).
    As with SUSY, the experiments will decide this question.

  31. dan says:

    Dear Eric,
    “First, 4D supersymmetry may be established by the detection of superpartners at LHC.”

    As string theorist Eva Silverstein pointed out, she and other string theorists think there’s a good chance LHC won’t find any evidence of SUSY. While it’s understandable that Tevatron may not have enough energies to explore EW scale, what will become of string theory/M-theory in the event of an LHC SUSY-null result? (i.e finding a single higgs and nothing else). Does Eva and other statements reflect this possibility, and hedging the bets of the future of string community?

  32. Eric says:

    Hi Dan,
    I don’t think that most string theorists believe that LHC won’t find any evidence for SUSY. Only those who’ve become enamored of fine-tuning think this way. For the most part, Silverstein, Kachru, etc., I think prefer this over supersymmetry because they didn’t invent supersymmetry. On the contrary, they invented fine-tuned models such as KKLT, and because they have so much confidence in themselves, believe these ideas must be right.

  33. dan says:

    Hi Eric,

    well NIMA ARKANI-HAMED “My hunch is that there’s a better than evens chance that supersymmetry will show up at the LHC”

    I’ve heard quotes from some Tevatron experimentalist the odds of finding SUSY are more like 5%. Could it be Eva invented such models to provide string theorists a way out should LHC provide a null SUSY result?

    If LHC does provide a null SUSY result, and finds only a single higgs plus SM only, how will affect the future prospects of string theory research program? What would it mean to both education and string theory research to say that for every fermion in the SM, there is a SUSYpartner boson, not seen even by LHC energies. What does string theory community have as an alternative in the event of this experimental result?

  34. Eric says:

    Arkani-Hamed has his own favorite alternative to low-energy supersymetry, namely split supersymmetry with large extra dimensions. It’s not surprising that he wants his own model to be true rather than low-energy supersymmetry.

    As far as the 5% figure you are quoting, I believe that may be the odds for discovery at the Tevatron. At LHC,I would put the odds at at least 50%. If low-energy supersymmetry is not discovered at LHC, then it is not the solution to the hierarchy problem. In this case, one may expect one of the alternatives to show up, either large extra dimensions or technicolor. A very, very small chance that only the SM Higgs and nothing else is found.

    At this point, all signs point towards low-energy SUSY.

  35. anon. says:

    Eric said:

    split supersymmetry with large extra dimensions.

    Huh? Those are two completely different and unrelated things, and there’s no good reason to put them together. Are you referring to an actual paper, or just combining buzzwords?

    Also, KKLT isn’t inconsistent with TeV-scale supersymmetry. The fine-tuning is in the cosmological constant; no one has yet figured out an alternative solution to that one….

    You seem strangely eager to assign suspect motivations to perfectly respectable physicists.

  36. Eric says:

    Sorry, I meant to say split susy or large extra dimensions, both ideas of which AH has contributed. Regarding KKLT, the point I was trying to make is that KKLT is a fine-tuned solution to the cc problem, and if you believe this is how nature works, then you are free to believe that the electroweak scale is fine-tuned.

    As far as my eagerness to assign suspect motivations, please calm down. We know how people are and how the real world works. As far as the public statements of the aforementioned persons regarding supersymmetry, my opinion is that they are simply pushing their own ideas and dissing the main competition.

  37. dan says:

    “At this point, all signs point towards low-energy SUSY.”

    What signs do you refer to? g2 muon magnetic dipole moment, or something else (or more)

  38. anonymous says:

    Regarding the public statements on SUSY: this part of
    the discussion
    started with a quote that Silverstein “would not be
    devastated if SUSY is not found”. The end of her quote
    in the telegraph article is something like “On the other hand, supersymmetry fits well with some existing
    observations, and it will be
    spectacular to finally learn whether it arises.” How do you
    go from this “not devastated” statement
    to claiming she (or anyone else) is making
    a prediction of no SUSY, based on ill motivations to boot?
    I have heard Eva
    emphasize in talks that SUSY requires rather special choices of
    compactification manifold, etc., and that there are
    arguments going both ways in terms of which is
    easier to construct from string theory and so on;
    she also writes papers on
    SUSY model building some of the time, citing the usual
    motivations. Anyway we need the LHC to tell us.

  39. Eric says:

    I don’t assign any ill motivations to Eva or Nima, only that they, like most people, have a built-in bias towards their own favorite ideas. It’s obvious to anyone who reads between the lines that they prefer one of the alternatives to low-energy supersymmetry to be discovered at LHC. This is not to say that they are trying to mislead anyone. It is in fact possible that one of these alternatives will turn out to be right. However, one shouldn’t read these statements as if they know something about the prospects for finding supersymmetry that the rest of us don’t.

    In any case, their ‘insight’ is most likely based on their current knowledge of the landscape of flux compactifications, where it’s quite easy to find vacua with a low string scale (the large volume models) or where supersymmetry is broken at a very high scale. However, there are no fully realistic models where this occurs, so noone should take these ideas too seriously. Indeed, until there is a completely worked out example or examples of the low-energy physics we observe, it’s simply impossible to make any judgments at all. To do so puts too much faith in our current understanding of string theory, which is far from complete.

    There are lots of hints that low-energy supersymettry exist. Gauge coupling unification, g-2 for the muon, and so on are some of these hints. However, I think the indications from experiment of where to expect the Higgs mass are the biggest hints that the MSSM is the correct model.

  40. g-2 for the muon

    What is the latest state of affairs concerning this? In


    I see that a deviation of by now 3.2 sigma has been reached. At the time of the writing of the review


    of Muon g-2 implications on susy physics just a few months earlier, it was still reported as being 2 sigma.

    So I suppose it is clear by now that there is a real beyond-SM effect seen in Brookhaven?

    What’s the implication for the susy parameter space as searchable by LHC?

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