SLAC Physicists Develop Test For String Theory*

The SLAC web-site today has a feature article entitled SLAC Physicists Develop Test For String Theory*. The “*” refers to a footnote to the title saying “Under Certain Conditions”. This is about the 10500th news story making this kind of announcement that has appeared over the past twenty years (like this recent one), and the title is just as incorrect and misleading as all the others.

The story starts with

String theory solves many of the questions wracking the minds of physicists, but until recently it had one major flaw — it could not be tested. SLAC scientists have found a way to test this revolutionary theory, which posits that there are 10 or 11 dimensions in our universe.

and is about a paper by JoAnne Hewett, Ben Lillie and Thomas Rizzo entitled Black holes in many dimensions at the LHC: testing critical string theory. This paper is perfectly reasonable, discussing a proposal for getting information about the number of extra dimensions, assuming Tev-scale gravity (a huge assumption most people think unlikely) and thus production of black holes at the LHC. If the number of extra dimensions is bigger than 6, then 10d superstring theory is ruled out (one can make similar comments about 11d M-theory, whatever that is).

Like all news articles of this kind, this one is misleading in the extreme, since “SLAC Physicists Develop Test For String Theory” is likely to make the unwary think that string theory is now testable. In addition, it’s flat out wrong, since the writer made the critical decision to replace “critical string theory” by “string theory”. Granting the unlikely assumption that the LHC sees extra dimensions and measures their number. if this turns out to be more than 6 or 7, string theorists will likely just point out that it is only “critical” string theory which lives in 10 dimensions. In recent years there has been much talk about string theories outside the critical dimension. For some discussion of this, see the comment thread of a recent Cosmic Variance posting, where string theorists Eva Silverstein and Clifford Johnson maintain that they see reasons to believe in the existence of string theories in dimensions other than 10. For some flavor of the discussion, here’s what Clifford has to say:

…the “person on the street” all too often hears (or implicitly gathers from posts like this) the phrase “string theory requires D=10/11″, and it is simply not true and in some years we may well have to be spending a lot of time undoing yet another uncautious claim when/if after doing phenomenology better we find that we don’t need to start in higher D and then “compactify”. We’ll have to go around telling everyone (on the tv shows and radio shows and magazines) “oh…that thing we said about extra dimensions? We were just kidding”…. Just like we’re doing now with the whole “unique vacuum” and “theory of everything” phrases…

Clifford seems fond of the idea of sub-critical strings, perhaps even strings in four dimensions (another enthusiast of this idea is Warren Siegel), while Stanford string theorist Silverstein advocates the study of super-critical strings, exactly the ones that would get around the “test” promoted today by her colleagues at SLAC.

Update: SLAC has replaced this article on their website with a new, much more accurate version, entitled “SLAC Physicists Develop Framework-Dependant Test For Critical String Theory”. The original version got wide distribution, even appearing on Slashdot.

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20 Responses to SLAC Physicists Develop Test For String Theory*

  1. D R Lunsford says:

    Heh, thanks to you, Peter, they can’t get away with this kind of thing now!


  2. Lubos Motl says:

    The experiments are exactly designed to distinguish between the different scenarios how many dimensions there are and how large they can be, and so on. We won’t get the full information from the very beginning, but we will of course learn something.

    As a conservative who believes a big desert after SUSY followed by a GUT scale near the Planck scale, I of course guess that no one will see mini black holes etc., but many of these scenarios are perfectly plausible and we will see how the experiments decide.

    Of course that only anti-scientific activists think that string theory is permanently untestable. String theory is, using an extremely modest language, the framework that parameterizes the space of reasonable possibilities for new physics potentially connected with quantum gravity, and although we can’t say with certainty which of these scenarios are correct, we can definitely eliminate many other scenarios that would be possible if we did not know the things arising from string theory.

    And on the contrary, we know scenarios that we would never invent if string theory did not guide us.

    Well, I completely understand that you are scared of the experiments more than the radical Muslims are scared of pictures of Mohammed – because you have spent years if not decades by spreading crap about the end of physics. Well, maybe you will survive, Peter.

  3. blank says:

    Peter, why must you be so fact-obsessed?

    Good thing there was a good apparatchuk on hand to put things in proper context.

  4. The Anti-Lubos says:

    We won’t get the full information from the very beginning, but we will of course learn something.

    This was Peter’s entire point. The headline makes it sound like we will get the full information from the very beginning. Surely, a smart boy like you can understand this.

    many of these scenarios are perfectly plausible and we will see how the experiments decide.

    Again, no one said that they’re not; the contention was merely that this does not constitute “a test for string theory.”

    Well, I completely understand that you are scared of the experiments more than the radical Muslims are scared of pictures of Mohammed – because you have spent years if not decades by spreading crap about the end of physics. Well, maybe you will survive, Peter.

    Mmmm, delicious, nutritious ad hominem argumentation! Allow me to participate: Lubos is a jerk.

  5. woit says:

    “radical Muslims are scared of pictures of Mohammed”

    “Maybe I will survive”?

    Is that some kind of bizarre threat? Lubos, you really are getting mad as a hatter and need to seek professional help.

  6. JoAnne says:

    Anybody who has ever spoken to reporters understands that what generally comes out in print basically does not resemble, in any way, your conversation with the reporter. Tom Rizzo and I spent about an hour with the reporter, explaining all the and’s, if’s, and but’s of our analysis. None of which were included in the first draft of the story. We tried hard to clarify the description of our work in the story, and ended up with the simple asterisk “under certain conditions.” And, to be fair, we were told that this story was intended for the general audience at SLAC, including admins, technicians, cafeteria workers, etc, and thus all of the details simply could not be explained. As for the headline that is blazened on the SLAC home page – I saw it for the first time when someone drew my attention to it. I knew it was going to cause headaches….

  7. Chris Oakley says:


    I am happy to listen to reasoned scientific argument from you. Even your polemics are sometimes amusing. But threatening me with the US Marine Corps or Peter with some unspecified hit man is just pathetic.

    I cannot believe that you can be a researcher of any great calibre. Anyone with talent will be used to receiving and, for that matter, dishing out strong criticisms of ideas without taking it personally. This is all part of the process of doing research. If you cannot handle criticism you should not be doing research.

  8. woit says:


    I figured that’s what had happened. Unfortunately there’s an irresistible urge present among journalists who don’t know much about this field to turn everything into this “scientists figure out how to test string theory” story. If only they all read my blog….

  9. Chris W. says:

    I think one can safely regard LM’s behavior as an example of an occasional and fading Central European penchant for abusive pedagogy: “I’ll beat the truth [as defined by me] into you even if it kills us both, you worthless insect!”

    (Peter: I don’t think this is any worse than “mad as a hatter”.)

  10. secret milkshake says:

    to the question of a “fading Central-European pedagogy penchant”:

    You won’t find too many people like this in Prague; we export them

  11. Boaz says:

    Not to say that Lubos statement wasn’t abusive, but I wouldn’t say it was a threat. He was suggesting that Peter is so afraid of experimental results that may support string theory, that they may kill him, but he might survive. As usual he takes a very extreme interpretation. PW says that headlines about interpretations of experiments are overhyped, LM responds by saying that PW must be deathly afraid of said experiments. One does wonder to what extent it is really posturing and trying to win a propaganda battle, and to what extent he really holds these views. I suppose Chris W.’s interpretation as an abusive form of pedagogy may be right.

  12. woit says:


    Thanks for the interpretation of the Lubos rant. I was honestly having trouble figuring out what is was that might kill me, and what the radical Muslims had to do with it (not that I spent much time trying to puzzle this out, I admit). Now I see, it’s those experimental results on black holes at the LHC that Lubos doesn’t believe we’ll get. Makes perfect sense now.

  13. Quantoken says:


    Oh you are so nice! But please do NOT believe a word Joanne said above. Come on, Joanne, don’t insult people’s intelligence by blamning it all on journalists. If it’s just one occasional super string theory hype news story, you can have an excuse on journalists not doing their homework. But when there are “10^500” of such types news stories (in Peter’s word) out there, all those are jouranlists fault and nothing of you string theorists doing? Come on! What about Kakuism we see daily? What about your own words quoted in quotation marks in the news story? Are they not misleading the people? Are they not your own words?

    Journalists LOVE controversial stories. Had you bee a little bit more honest, you could have meantioned to the Journalists that there is a different opinion about string theory, for example from a guy called Peter Woit. The journalist would then love to track Peter down and write up a much more balanced news story.

    And NO, you do NOT need to go to any technical details in order to decribe to the public the honest truth of the current situation in the field of super string theory. It can be said in plain English: it’s a failure so far and there is little hope any meaningful progress can be made in the next few decades. It’s a matter of honesty whether any string theorist is willing to tell that evident truth in plain English.

    All the string theory hype stories are the makes of the string theorists themselves. Journalists simply report what you guys told them and you can’t blamn journalist for telling an untrue story if you don’t tell them the true story in the first place!


  14. Juan R. says:

    I find really interesting that now string theorists as Eva Silverstein and Clifford Johnson maintain in public they see reasons to believe in the existence of string theories in dimensions other than 10 specially the case 4D.

    In my Oct 21 post “String theory is not a TOE” in moderated newsgroup sci.physics.strings i did a joke about the infinite malleaibilty of string theory and how even with a “blanck check” -i.e. you can fix anything in the “theory” (even there are versions of string theory without strings!)- they were not advancing science. In page 2 of my April non-technical work, i cited the history of dimensions on string “theory”:

    4D,… 26D, 10D, 11D, 12D?,…4D again,…

    It looks like researching in circles 🙂

    Juan R.

    Center for CANONICAL |SCIENCE)

  15. A.J. says:


    Joanne is an experimental particle physicist. Get a clue.

  16. woit says:


    No, Joanne isn’t an experimentalist, she a theorist, but of a phenomenological sort, definitely not a string theorist.

    Over the last twenty years it has been interesting to watch the relationship between phenomenologists and string theorists, the two dominant groups within the particle theory community. It began with a certain amount of active hostility (think Glashow, who has stuck to his guns), but with the advent of extra dimensional models, there was a definite rapprochement and cessation of hostilities. The phenomenologists could study models with extra dimensions visible at the TeV scale, and thus at least in principle their work might have something to say about string theory (e.g. Joanne’s work), and the string theorists could announce that string theory had potentially testable experimental applications.

    My personal opinion is that, in this relationship, the phenomenologists have quite often found themselves used as tools in string theory hype. To some extent this story is just one more of a long line of similar examples.

  17. JoAnne says:

    First, as Peter says above I am indeed a phenomenologist – the type of theorist who connects formal theory to experiment. I tend to get irritated when people call me a string theorist. Particle theorists are not all string theorists.

    Second, this news story is now all over the web. The research in this paper is honest and credible and now it is being blown out of proportion and misrepresented all over the web. Nothing could make me more upset.

    I am not having a good day.

  18. A.J. says:

    Whoops. Looks like I need a clue, too. I’m sorry for misidentifying your profession, JoAnne.

    Of course, my mistake does not excuse Quantoken’s misdirected personal attack. It would be unacceptable in person, and it’s unacceptable on the internet.

  19. Tony Smith says:

    As JoAnne says, “this news story is now all over the web”, including slashdot, where you can see:

    a link to Peter’s blog (this entry);

    that JoAnne was at Iowa State in the 1980s;

    that Ben Lillie says that he has “… replaced the arxive version with the published version: …” so that anyone can read the serious physics without the PR hype; and

    that Ben Lillie also says “… The main point is that there are many “ifs”, “ands”, and “buts” in the paper that did not make it into the news release. … It certainly can not rule out string theory. We think it’s an important and interesting piece of work, but it isn’t a definitive “test” of string theory, as the headline suggests. …”.

    Tony Smith

    PS – JoAnne also said “… I am not having a good day. …”.
    The situation reminds me of Dilbert cartoons, with JoAnne/Ben/Tom as Dilbert the Engineer and the SLAC PR creatures as Marketing-Sales-Weasels.
    Don’t let Marketing-Sales-Weasel idiocy get you down. Most people in the real world understand that Dilbert is not the bad guy.

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