String Theory’s Next Top Model

I’ll write soon about the conference I spoke at today in Lisbon. A few hours ago I participated in an interesting discussion about some of the issues around string theory with two string theorists. One of them was quite vehement that a big part of the problem is things being hyped to the media, and that this is an American disease, something that doesn’t happen to the same degree in Europe.

I think he may be right, since I certainly haven’t noticed as much media hype (either pro or anti-string) from European sources, although I follow US ones more closely. When I got back to the hotel this evening, I noticed that SLAC is promoting on its web-site a news story about String Theory’s Next Top Model. The story appears to be about this paper that was just published in Physical Review D. In it, the authors consider three toy models of inflation in string theory and find that they don’t work. Their conclusion:

This may be an artifact of the simplicity of the models that we study. Instead, more complicated string theory models appear to be required, suggesting that explicitly identifying the inflating subset of the string landscape will be challenging.

So, the gist seems to be that they went looking for toy models of string inflation, didn’t find a workable one, but decided that this was worth a SLAC press release, presumably because “string theory is currently the most popular candidate for a unified theory of the fundamental forces”, so one should go to the press with any result one gets, even if negative. I think the Europeans may be right that this sort of thing doesn’t happen here….

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11 Responses to String Theory’s Next Top Model

  1. Who says:

    This is how the New Scientist handled that same paper on 11 September.

    They quoted Mark Hertzberg (I gather the lead author), Max Tegmark (a co-author), and Andrei Linde (who criticized the paper.) Fairly balanced job, to NewSci’s credit. Interesting paper raising interesting question.

    Also quoted Paul Steinhardt:

    Paul Steinhardt of Princeton University in New Jersey, US, who helped to pioneer the theory of inflation, says the findings are in agreement with work that he and others have done using other versions of string theory.

    “I think the fact that it is difficult to combine inflation and string theory is very interesting,” he told New Scientist. “It could mean they are completely incompatible, which would force us to abandon at least one of them.”

    This time David Shiga at NewSci comes out looking better than whoever it was at SLAC public relations that talked to Kachru.

  2. DB says:

    String Theory Hype is not just an American disease, though clearly that’s where it started and reached epidemic proportions. Britain has also been infected, for years they have been “treated” to breathless expositions from the likes of Kaku and Greene, specially imported to create programs on the subject for BBC’s Horizon series, for example.
    Recall also that New Scientist is a British based publication.
    I don’t believe Continental Europe has succumbed to the same degree.

  3. moron says:

    A similar promotion of complexity as advancement happened with the theory of epicycles in about 150 AD. Everytime Ptolemy tried to predict something new with his model, it turned out wrong so more epicycles and more complexity was added to make it work.

    His reaction was always, “Great! I’m discovering more exciting knowledge about how complex nature really is!”

    Ptolemy would then announce the great news about his “Exciting Discovery of Complex New Epicycles” by a press release to the geeky Novus Scientist in Londinium.

    My Latin is a little rusty, but the gist of his final press release was: “Ptolemy’s mainstream earth-centred universe theory is obviously true. It’s led to some fantastic maths for working with epicycles, and it’s also the most popular idea around. It’s the only game in town. Aristarchus’s simplistic solar system is crackpotism.”

  4. Who says:

    To focus on what we’re looking at, the key paragraph in NewSci was

    The study was carried out by a team of researchers led by Mark Hertzberg of MIT in Cambridge, US. The team tried to produce inflation in three versions of string theory in which the extra dimensions are shaped like a doughnut – the simplest possibility. But they found that the conditions needed for inflation appear to be impossible to achieve in these simple versions.

    In the cases studied, the space required by strings cannot inflate. Which is serious because prevailing cosmology needs inflation to have occurred. What follows in the article are quotes taking various sides on the issue (from Andrei Linde, Max Tegmark, Paul Steinhardt…)

    Nothing as clear and forthcoming as this paragraph occurs in the Stanford press release. My guess would be that issuing the Stanford press release was the idea of Shamit Kachru, who may have chosen not to be quoted in the September article, but who may later have wished an opportunity to put his own interpretation on the group’s findings (without the inclusion of quotes from other authors of the paper).

  5. blogguy says:

    It doesn’t appear to be a press release at all. I think it is just an article in the daily SLAC paper, which Peter has decided to call a press release. (I say this because there are profiles of recent work by other SLAC physicists regularly appearing on that site). It would be an odd press release, since it doesn’t claim to have discovered something, only to concern a direction of work in progress.

  6. Peter Woit says:


    I actually first saw this at

    a news site where most of the content is items put out by press offices of universities and labs. This article was put out by the SLAC press office, written by one of their staff. You are right though that it is not something they officially call a press release.


    Having two press stories about a paper which quote different authors with opposite spin on the paper’s results is kind of odd. It’s also odd to have one, much less two press articles about a paper dealing inconclusively with toy models. But then again, the press coverage of string theory has often been odd.

    My impression of how these things get written is that it is unlikely that Kachru contacted the SLAC press people asking them to write about this. More likely, what they do as part of their job is to call people at their institution up and ask them if they know of any work going on at their institution that they could write a story about. If a press person calls one up expressing an interest in writing about something one has done, most people won’t turn them down.

  7. Stanford grad student says:

    More likely, what they do as part of their job is to call people at their institution up and ask them if they know of any work going on at their institution that they could write a story about. If a press person calls one up expressing an interest in writing about something one has done, most people won’t turn them down.

    I can personally attest to the fact that this is essentially exactly how many SLAC Today articles work. But SLAC Today is little more than a daily site-wide newsletter. It’s handled by the press office, but it’s not meant to be cutting-edge, breaking-news, press-release kind of science material.

  8. Coin says:

    “I think the fact that it is difficult to combine inflation and string theory is very interesting,” he told New Scientist. “It could mean they are completely incompatible, which would force us to abandon at least one of them.”

    So, I was going to ask if this could eventually somewhere bring us within striking distance of a “falsifiable prediction” for string theory (i.e., no inflation), but the same article seems to scuttle that hope:

    Andrei Linde of Stanford University in California, US… says the results only apply to a class of string theory versions called type 2a, which are irrelevant to the real universe because they have been shown to be incompatible with dark energy, the mysterious force causing the universe’s expansion to accelerate.

    So it looks like more than anything this is turning into another case where String Theory tells us you can have things one way if you choose one model, or another way if you choose a different model, and then there’s some other classes of models where we aren’t quite sure which way it goes…

    On the other hand, if we conclude inflation is too precious to give up, could a serious program of trying to get toy-inflation out of other topologies besides the “doughnut” one finally allow us to “drain” some of that “swampland” I keep hearing about in the string theory landscape? It seems like I was hearing a bunch at one time about how the next step in the landscape program would be to get some of that swampland drained, but if there’s been any progress in that regard I’ve somehow not managed to hear about it.

    Does ruling out type IIA string theory, or one particular simple background geometry, rule out any quantifiable proportion of the string theory landscape (if we’re assuming inflation)? (Or have we really not gotten anywhere at all, since it’s possible that we were just not using a sufficiently complex variant of IIA string theory– as Tegmark suggests in the article to free type IIA from being ruled out on Dark Energy grounds– or possible we were using the wrong type of inflation? (Or for that matter, is it possible I’m just confused here and IIA is a different kind of string theory altogether than the one that produces the oft-discussed “landscape”?))

  9. Eric says:

    Usually when talking about the landscape, people are talking about Type IIB flux compactifications, which are T-dual to Type IIA string theories. It’s doubtful that they’ve ruled out inflation for all such possible compactifications. More likely, just for the simplest type of model. In any case, eternal inflation is a principle idea needed to populate the landscape. If most string compactifications cannot inflate, the one might expect the landscape to be lightly populated. In fact, inflation may be ‘vacuum selection principle’. If we’re lucky, there will be one and only one string vacuum where inflation can work, and this vacuum will contain the Standard Model. But this is just speculation…

  10. Coin says:

    Eric, thanks.

    One question, would T-duality be enough to conclude that the Physical Review D results do apply to IIB flux compactifications? (Or at least whichever flux compactifications correspond under IIB to the one particular kind of calibi-yau manifold they considered in their IIA analysis).

  11. Annie says:

    I think the New Scientist article did a poor job. They spun the article unfairly, indicating that just because Hertzberg et al couldn’t inflate those simplified models, string theory was in trouble. This isn’t the case at all. The SLAC article points out their real goal–to find a simplified model for the purposes of understanding string theory and inflation. And as Stanford grad student says, the SLAC Today articles aren’t press releases; they’re intended for the SLAC community to let them (astrophysicists, particle theorists, engineers, students, construction workers, etc) know what’s going on. PhysOrg takes any science article from SLAC Today and puts it on their page, without any prompting from SLAC.

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