On Status of KKLT

(Warning, this is just more about the topic of the last posting, which for most people will be a good reason to stop reading now. On the other hand, if you’re obsessed with the controversy over string theory, you might find this interesting).

I finally got around to watching some more of the Simons Center Workshop on the Swampland talks, and noticed a remarkable exchange at the end of Thomas Van Riet’s talk On Status of KKLT (starting at 1:30). The first commenter (a German, Arthur Hebecker?) starts off saying “I think you are doing something that is very dangerous”, with the danger being that KKLT will get thrown out and people will think that it is a “theorem” that string theory has no dS vacua. He is interrupted by Vafa who tells him that “your statement is defamatory, let’s calm down”. The German goes on to explain to Vafa the significance of the danger he is concerned about:

Maybe for you in the US it’s fine at Harvard, for me it will be a pain because people will turn against me. The little standing that string theory and new physics at all has in Germany will be harmed by a backlash on us that we have been talking nonsense all the time, which is not true.

Van Riet after a while interjects that there is an even worse danger:

The opposite happened and actually back-reacted very badly. We had the books by Woit and Smolin and it was based on the existence of the multiverse as a correct statement, right? And that’s when the criticism of string theory took off, right?

Someone else in the audience (Iosif Bena?) comes in on the Vafa/Van Riet side of the argument, criticizing multiverse mania:

I think the main problem was that at the beginning people in the KKLT camp, they came up with, “OK string theory has the multiverse, we’re not going to do physics anymore, the anthropic principle…” They came up with all these ideas that hurt string theory much much worse, at least in Europe, at least in my part of Europe. And you know, essentially hurt us heavily… Then there were these books by Woit and Smolin that were very popular…

It’s remarkable to see publicly acknowledged by string theorists just how damaging to their subject multiverse mania has been, and rather bizarre to see that they attribute the problem to my book and Lee Smolin’s. The source of the damage is actually different books, the ones promoting the multiverse, for example this one. A large group of prominent theorists, especially many from the West Coast, including the group at Stanford and the late Joe Polchinski at Santa Barbara, used the existence of the KKLT construction to push very hard a pseudo-scientific excuse for why string theory wasn’t working out. I’ve often point this out, and I do think this has been very damaging to the public perception of string theory. But the underlying problem is the takeover of string theory by multiverse pseudo-science, not that I and Lee Smolin criticized it.

A striking fact about the Stony Brook workshop is that none of the participants were from Stanford, and none of the many prominent figures responsible for promoting KKLT were there. It looks like there is now a dramatic split going on, with Vafa leading the charge to try and fight back against what in recent years has been a seeming dominance of string theory by the pro-multiverse faction. I think such a split is long overdue, that most string theorists for years now have been making a terrible mistake by going along with multiverse pseudo-science. As Hebecker(?) explained though, fighting back publicly at this point carries its own dangers. In particular, many observers will be asking: “for years you told us about the 10500 vacua”, now you say that maybe there aren’t any. Which is it? Why can’t you tell? And do you really have a serious alternative for how to connect string theory to the real world?

Vafa tries to not take sides, to portray this as a simple technical question that will yield to further calculations by theorists. Where I disagree with him is that I’m very skeptical that this is a technical question with a well-defined answer. This is not a new controversy: theorists have been arguing about moduli stabilization and this de Sitter/no de Sitter issue for twenty years or so, without coming to any firm conclusions. If you watch the technical talks at the Stony Brook workshop, the degree of technical complexity of the arguments is striking, as is their often rather vague nature. What you don’t see is a specific set of equations that everyone agrees on. We’ll see what happens in coming months and years, there are likely to be a large number of papers written on this subject. Also to look out for, likely the efforts of Vafa and others to throw doubt on KKLT will not be taken lying down. The West Coast Empire will strike back…

Update: At CNN, Don Lincoln has an article about this, which ends with:

It’s not quite a WWE cage match, but it’s going to be fun to watch these theories fight it out.

Update: Tonight the West Coast Empire has struck back, defending here and here their dS vacua against the Swampland attack, and going on the offensive, accusing the conjecture of their attackers as being “ruled out by cosmological observations, at least at the 3 sigma level”.

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15 Responses to On Status of KKLT

  1. Sabine says:

    (Yes, that’s Hebecker.)

  2. Bai says:

    As a complete outsider to HEP (I am a condensed matter physicist though), I find appalling that issues like the damage being made to a community (in certain parts of the World..) are openly discussed and considered at Scientific events. It makes it so explicit that some of these fellows (I suspect the vast majority..) give a lot of importance to avoiding their University chairs being shaken, their funding being cut, etc, than seeking the ultimate truth in their research. It is very sad to see the kind of game (hard) Science is becoming, and it all sets a terrible example for future generations…

  3. Peter Woit says:

    Bai,
    This exchange was interesting precisely because these issues, while important to people, are virtually never publicly discussed. This is not something that regularly happens. Also note that, in response to Hebecker bringing up the issue, Vafa and the others, while acknowledging the political problem, properly responded that such issues should not be relevant, that what was important was finding the scientific truth of the matter, whatever the political ramifications.

  4. Jesse O. says:

    “The West Coast Empire will fight back…”

    It is wholly irresponsible to come so tantalizingly close to an “Empire Strikes Back” pun.

  5. Peter Woit says:

    Jesse O.,
    Irresponsibility fixed.

  6. Joelson F. Silva says:

    In condensed matter theory theoretical physicists have your own “Vietnam War”, called high critical temperature superconductors, and for those thet believe in AdS/CFT approach to the problem, this method can “describe” only few properties of the problem as the pseudogap
    region and fails to most others real problems in condensed matter, for exemple, universal viscosity prediction for bad metals. However, is not about that I wanna talk here, seens to me that the string theory is the “Vietnam War” for high-energy physicists, but in condensed matter we recognize our “defeat”, even P.W. Anderson recognized your mistakes in the first approach to the problem. Many important things came from the High Tc superconductors search, as new numerical techniques, but we don’t find the answer to the problem, until today. We don’t give up of the High Tc supercondutors, we move on to new approachs and ideas, this was not easy, due the “fights” beetwen the Popes of the area and the intimidation over the new
    researchers and your ideas. I think that HEP physicicts must do the same, move on to new ideas outside string theory, in this sense, the Woit work and others are fundamental. The first step to the string theorists is recognize the “defeat” in this “Vietam War”.

  7. Lee Smolin says:

    Dear Peter,

    I have usually stayed silent in the last 12 years since my The Trouble with Physics was published, but given the remarks you quote, I think its important to remember some key points:

    -Leonard Susskind’s paper, “The Anthropic Landscape of String Theory (0302219)” was posted in February of 2003. This immediately ignited the controversy over KKLT and the landscape; Susskind’s book The Cosmic Landscape, written to bring his polemic to a large public audience was published in December 2005. By the time my book appeared in September 2006, the controversy had been going for 3 and a half years. Several prominent science journalists told me my discussions of the landscape were already old news.

    -Indeed, the issue of there being a vast landscape of string theory vacua, and hence a problem of predctability, was widely know back to papers of Strominger and others back to 1987. It was the motivation for my 1992 paper on cosmological natural selection; indeed I introduced the term “landscape” in the context of that work, borrowed from population biology. What was new in 2003 was only that KKLT addressed the issue of whether there are any string vacua for positive cosmological constant.

    -Many people criticized my book without reading it, quoting others who also had not read it. Many who did read it commented, publicly or to me, including several string theorists, that the book had been mischaracterized and was not a simple “attack on string theory”. Several praised the book for its fair and balanced treatment of the successes and failures of string theory, that was in detail, little different than that given in Brian Greene’s book of the same year.

    -The subject of the book was very different, it was the role of controversy and disagreement, and how they are resolved, as engines which drive progress in science. String theory was there as a case study.

    -Nonetheless, I would claim the critique of string theory’s strengths and weaknesses has largely held up over the 12 years since. The successes are still reasons to consider it one of the candidate approaches to QG. The big open problems I elaborated there: the lack of a background independent formulation, the absence of a proof of uv finiteness to all genus, and the problem of testibilty, are all still unresolved. In the time since a great deal of good work has been done on related topics such as AdS/CFT, little of which, however, addresses these key open issues.

    -The book advised that string theory be studied as one of several approaches to QG, which have complementary strengths and weaknesses. Each is interesting, none is problem-free. Indeed my previous book Three Roads had suggested a route to unification of string theory with LQG. These remain valid, reasonable views.

    -Of course, others will disagree. As TTWP argued, this kind of friendly, respectful, disagreement is necessary for science to progress. Given that, we should all welcome a diverse scientific landscape, especially to leave room for young scientists to discover better theories, for this is how science progresses. That remains the message of the book I wrote.

    Thanks,

    Lee

  8. Peter Woit says:

    Hi Lee,

    Thanks providing some valuable perspective on your book.

    As for my book, I can’t help but mention that the original version was mostly written in 2002, pre-Susskind/landscape. There is nothing in the version of the manuscript submitted to Cambridge University Press in early 2003 about the landscape/multiverse/anthropics issue (basically because I was unaware of it). If string theorists hadn’t managed to stop CUP from publishing that version, mine might have appeared with nothing about this topic in it. The chapter on this topic was added in 2004, in the version that Jonathan Cape later published.

    Personally, I think the arguments of both books have held up very well over the years since they were written, much better than those of contemporaneous books enthusiastic about the prospects for string theory, supersymmetry, extra dimensions. But I think string theorists are wrong to attribute their problems to the books. Their problems are with the science, not with the fact that some people pointed out the scientific (and sociological) problems.

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  10. Shantanu says:

    Peter, was Strominger at this meeting? IIRC he is not a fan of landscape or anthropics. (see his colloquium at Harvard which you had blogged about) Does he side with Vafa on this issue?

  11. Peter Woit says:

    Shantanu,
    No Strominger, and I assume his point of view on this is probably the same as that of most people’s, string theorists and non-string theorists: landscape/anthropics is a dead end, and no point in wasting time on arguing about the complex details of whether Rube Goldberg machines like KKLT really work or not.
    .

  12. Hello Dr. Woit, in your posting you write: “[Various key theorists] … used the existence of the KKLT construction to push very hard a pseudo-scientific excuse for why string theory wasn’t working out.”

    I want to make sure I understand this comment. You are saying that due to the existence of the KKLT paper, the community of theorists–or at least a faction of the community–was able to “fend off” the “dark energy versus aDS” issue for a long time without being “called to account” for the conjectural nature of KKLT. Is this correct?

  13. Peter Woit says:

    Jeff Berkowitz,
    No. The significance of the KKLT paper is that their mechanism produces not just one “solution” with positive CC, but an exponentially large number of them. It is this huge number of solutions that has been used as basis of the claims by a group of theorists that string theory implies both an (anthropic) solution to the CC problem, and suggests that what we think of as fundamental constants that should be calculable, instead are environmental. It is this aspect of KKLT that I think motivates Vafa and others to try to find an argument against it, hoping to kill off the “landscape” pseudo-science this way.

  14. Narad says:

    >If string theorists hadn’t managed to stop CUP from publishing that version

    I seem to have missed this story. Could you elaborate or provide a pointer, please? I was in journals publishing, but we were close with (supporting, actually) the books division at the university press I worked at, and although CUP is much larger organization, acquisitions editors are practically on a quota basis.

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