Hype or Not Hype?

The high point of my expertise in condensed matter physics was about thirty years ago, when I studied the subject in order to pass one of the general exams at Princeton. At the party after the test was graded, Phil Anderson came up to (after a fashion…) compliment me, noting that he was glad to see that even though I hadn’t been able to solve one of the condensed matter problems, I had known enough to realize that the calculation I was trying to do was giving a result that couldn’t be right and had written that on the test.

Since then, my little understanding of the subject has slowly decayed over the years, so I’m in no position at all to evaluate claims made about new advances. Recently there has been a lot of interest in applications of gauge/gravity duality to certain condensed matter systems, and this week there’s a new article out in Science (not available on the arXiv itself, but based on this arxiv preprint), together with a press release from MIT. This has led to news stories headlined String Theory Explains Superconductors, and String theory and black holes show a possible path to practical superconductors. This latest story starts off:

A leading candidate for room temperature superconductors is the copper compound cuprate, but no one knew how cuprates facilitated superconductivity…until some brave souls looked inside a black hole and broke out the string theory to explain how they work.

So, hoping that there might be someone expert on this out there and willing to comment, what’s the verdict: hype or not hype?

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65 Responses to Hype or Not Hype?

  1. nbutsomebody says:

    Somebody,

    “About your other comments like p-wave etc.: the real high-Tc superconductors are d-wave, so I would say it is encouraging that a hard gap can be found by going from s to p.”

    Not a bad point ! I think one should write it up and I more or less know how to calculate it. Any interest of doing a “less fundamental” work?

  2. nbutsomebody says:

    onymous,

    Very nice description. This is also my realization although I am not a CM expert. However as you have pointed out it would be nice to have model which produces all the feature of cuprates phase diagram in one place. It would be nice if some CM expert correct those speculations.

  3. Seth Thatcher says:

    Peter, I just discovered your blog tonight, or rather this morning and find it extremely helpful both in posts and comments to understanding the ongoing temporal battles in theoretical physics. I am a layman and must admit that I have been taken in by all the Michio Kaku’s of the world and their seeming confidence in the truth of string theory. It is only upon reading this blog that I come to realize that there is a sizable contingent of physicists who regard string theory as bunk. So now I must ask the question-What, if any, theories are there that take the place of string theory in whole or in part? That question is not meant insult. I understand that many physicists may think string theory is incorrect while not having any ideas to what might be correct given the fascinating and elusive nature of our universe. Are there competing theories? Where can I read about them? Thanks in advance and I will be visiting often even if I only understand about 1/100th of what is discussed here.

  4. Yatima says:

    >>What, if any, theories are there that take the place of string theory in whole or in part?

    No-one knows. Indeed, is is not at all certain that we already have the mathematical tools to do it yet.

    I recommend Roger Penrose’s “The Road to Reality” as pretty good math-based “introduction”. He doesn’t refrain from proposing his own ideas in that Phone-Directory-Sized Wonder, but that’s ok. One of the books that take a few years to read.

  5. SteveB says:

    Seth,

    I recommend reading Peter’s book: Not Even Wrong. Very good reading. The standard model description is good and especially how mathematicians have contributed to the physics. Peter is very reasonable about asking for some verifiable predictions from a theory. I have read Peter’s book twice (so far). Also, I recommend Lee Smolin’s book, The Trouble With Physics. I just finished it and it is also very good.

  6. Peter Woit says:

    Seth,

    There are various competing ideas about how to get a quantum theory of gravity. Lee Smolin has written about some of them. There’s an interesting more recent idea that a certain standard supersymmetric version of general relativity may avoid the usual arguments that standard quantum field theory can’t give quantum gravity, but I haven’t seen a popular exposition of that.

    It remains true that there aren’t any good competing ideas about unification: how to put the Standard Model and quantum gravity together. The excitement over string theory was mainly due to its promise to achieve this, a promise which hasn’t worked out. So, right now we’re in a situation where every known proposal for a unified theory has very serious problems. My own point of view is that this means that people should be casting a wide net to look for new ideas, and not spending more time on failed ones. But in no way do I claim that the problem is that there is some great idea about unification that is being ignored in favor of string theory.

  7. stan says:

    … how to put the Standard Model and quantum gravity together. The excitement over string theory was mainly due to its promise to achieve this, a promise which hasn’t worked out.

    Oh dear, here we go again. String theory does of course provide fully explicit and calculable solutions that unite the Standard Model and Quantum Gravity (there is admittedly some fine print here, which we can discuss if need be), and I’m sure Peter knows this. The hope was that this problem was sufficiently constrained as to admit a more or less unique solution, hence being predictive — a hope that seems not to be realized. So string theory succeeded in unifying the Standard Model and Quantum Gravity. What failed was the dream that this would be enough to make experimental predictions. Any attempt to go beyond the Standard Model has to face up to this fact. The truth is that only String Theory has been pushed sufficiently far to encounter this fact of Nature.

  8. nbutsomebody says:

    Stan,

    It would be nice to know more detail about the string theory compactification you are talking about.

  9. Peter Woit says:

    nbutsomebody,

    I suppose one could point out again to “stan” that the statement that string theory unification hasn’t worked out is an uncontroversial one that even most string theorists agree with. But I fear that would be a waste of time…

    Enough about string theory unification hype, unless someone has something new to say. Otherwise, please return to the topic of this posting, whether claims that AdS/CFT explains high Tc superconductivity are hype or not.

  10. Shawn Halayka says:

    “There’s an interesting more recent idea that a certain standard supersymmetric version of general relativity may avoid the usual arguments that standard quantum field theory can’t give quantum gravity, but I haven’t seen a popular exposition of that.”

    That does sound interesting. I wonder if it would mean that hidden dimensions are effectively fictitious.

    Do you know where to find documentation on this idea?

  11. martibal says:

    Well, this comment is off topic regarding AdS/CFT and high Tc superconductivity, but totally in the topic regarding “Hype or not Hype”. Here is an article (in french)

    http://www.rue89.com/2010/08/23/les-freres-bogdanov-exagerent-le-succes-de-leur-dernier-livre-163583

    explaining how the Bogdanoff are exaggerating the success of the their new book (taking into account what they claim, they should have sold 50 000 copies in one single night !).

    What could be interesting for the readers of this blog, or at least funny, is the photo at the top of the article. It is amusing to see who-you-know on one of the most renown online-newspaper in France.

  12. Chris Oakley says:

    Re: the photo of the Bogdanov bros. with a former Harvard Assistant Professor – who is destroying who’s credibility?

  13. martibal says:

    Chris: good question ! It is fair to say that the photo is from 2008, and the former Harvard Assistant Professor has probably not been asked by the online-newspaper the authorization to publish the photo.

  14. Thomas Larsson says:

    I spent a week in Paris on vacation this summer, and noticed that the Bogdanoff’s new book was among the most exposed science books.

  15. martibal says:

    They are pretty popular in France (mostly because of their science/ science fiction show on TV 25 years ago) and their are still very present in the medias. Some people claim this is because they are quite close to one of the son of Sarkozy (at least they pretend to have worked with him on one of their TV program). It is just completely frightening to imagine they could be some scientific counselor of the president…

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