Quick Links

The speakers for Strings 2008 have been announced. One anomaly is that someone from the LQG camp has finally been invited, Carlo Rovelli. Another anomaly is that Witten won’t be speaking.

Remember last November’s “unmistakable imprint of another universe” which vindicated string theory? False alarm.

There’s a new X-files movie coming out this summer, The X-Files: I Want to Believe, with a plot that revolves around string theory and features Amanda Peet (no, not the string theorist).

Outside magazine has a profile this month of Garrett Lisi, and quotes from various physicists about last year’s media storm. I’m pretty much with Frank Wilczek on this, who says:

To my perception, Lisi hasn’t advanced the story. That said, I admire people who think for themselves and dare to take on reality directly rather than writing footnotes to fashionable literature. So I hope he keeps trying and inspires others.

I also hear that the New Yorker will have an article about this, to appear sometime during the next couple weeks.

Bert Schroer has a new version of his paper about String theory and the crisis in particle physics. It contains both sociological observations on the string theory phenomenon, as well as more technical arguments about how to think about a quantum theory of strings. Schroer was involved in endless battles on this blog a couple years ago over an earlier version of this paper. People who want to argue this again are encouraged to first read through the old discussion, and then see if there’s something new and interesting to contribute, rather than a rehash of the previous arguments.

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28 Responses to Quick Links

  1. Sara says:

    I’m very very happy they have choosen Carlo Rovelli as speaker, but I asked myself why they don’t have called Lee Smolin, for example, or somebody else.

  2. Coin says:

    Is it known what Rovelli might be talking about?

  3. Sulfur Surfer says:

    Schroer’s new paper claims that there are technical flaws in the understanding of string theory. However, the entire basis of his argument is incorrect. He begins by asserting that “string theory has no vacuum polarization.” He appears to draw this conclusion from the ultraviolet finiteness of the theory, and its S-matrix character, but this is a non sequitur and false besides. For example, the most notable physical consequence of vacuum polarization is the running of couplings; such running is observable in the S-matrix (and this is actually done in accelerator observations). The couplings do indeed run below the string scale in string theory, and exactly as they would in the corresponding effective low energy QFT.

  4. Jean-Paul says:

    Surfer — if you are so sure about running couplings, why don’t you compute just one on-shell S-matrix element that has “observable” running. You will see that all on-shell S-matrix elements are infrared divergent in D=4, already at the one loop level.

  5. Sulfur Surfer says:

    Jean-Paul — Sure, but the meaning of these divergences is taught in every QFT course, as is the cure – what particle physicists actually observe, and calculate, are IR finite cross sections with the detector resolution taken into account. You can substitute that long phrase for `S matrix’, but I don’t think that this was Schroer’s point.

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  7. Trent says:

    Peter,

    “….. see if there‚Äôs something new and interesting to contribute, rather than a rehash of the previous arguments.”

    Do you ever come up with new arguments? It seems to me you constantly are rehashing your old arguments. Or did I miss something? Do you actually have new arguments?

    Best,
    Trent

  8. Professor R says:

    Hi Peter, thanks for the reference to the Garrett Lisi article in Outside Magazine, it’s a good article once you get past the initial bombast. Given his lifestyle, I imagine Garret probably enjoyed this article more than any of the others!

    I didn’t know what to think about the Lisi story when it broke, but I’m glad this story is resurfacing, it’s a bit of light relief in our dull lives. ..

    While the Wilczek quote probably summs it up for most of us, there are a few points I’d like to make

    1. Every time journos draw a comparison with Einstein, Lisi patiently points out that the tenure issue is the only similarity – so it’s not his fault they keep making this comparison

    2. I don’t see the problem with the surfer angle – surely it makes a welcome change from the usual media view of scientists

    3. I’m delighted to see group theory get some attention – few outside the particle physics field have the slightest idea of the importance of group theory in this field…and even if the whole E8xE8 thing turns out to be a fairly trivial classification, so what? It’s very nice to be reminded of the eigthfold way, no harm at all

    I think we physicists are inclined to react strongly against media attention, especially if we feel there are more deserving cases. It’s a pity, because such stories probably do far more for the public perception of physics than any number of well-intentioned school visits! Cormac

  9. D R Lunsford says:

    Schroer makes a chilling point in his paper, one that I’ve often worried about – apart from derailing progress in science, the current environment is utterly corrosive of the collective understanding of known results – so the old theorists are something like stone masons without apprentices and with no more cathedrals to build, and as they pass on, they take their hard won knowledge and experience with them. I know in my own area, completely separate from QFT, I find a shocking ignorance of basic things among my juniors. Of course the knowledge is still there, on the books that no one reads, in the history that is ignored. It does no good if someone does not own it. This to me is a tragedy beyond expression.

    -drl

  10. David Nataf says:

    Am I the only one who found the profile of Garrett Lisi offensive? The article refers to him as a “hobo” and a “surfer bum”.

  11. MIchael says:

    Trent wrote:

    “Peter, … Do you ever come up with new arguments? It seems to me you constantly are rehashing your old arguments. Or did I miss something?”

    The argument “String theory does not make predictions” is so strong that it does not need new ones. String theorists should take it as a challenge. The fact that they don’t is telling.

  12. Mitch Miller says:

    David,

    Do you find it offensive to Lisi or Bums?

    (Not a dig at Lisi, as I think he used those terms to refer to himself so I don’t see how it could be offensive to the former)

  13. David Nataf says:

    I think the term “hobo” is very derogatory of the homeless and should not appear in a respectable publication, with the exception of paraphrasing. Language is very important.

  14. Professor R says:

    P.S. Thanks for the listing on the website Peter, I hadn’t noticed it!

    Re Schroer paper, I’m still wading through it. Broadly speaking, I find myself in agreement with most of his points. However, it seems to me that one big point is conspicuous in its absence (so far). ..

    Nobody asked nature to get more complicated mathematically, the more we probe the world of the sub-atomic, and attempt to describe it. That just seems to be the way the cookie crumbles, so far. Of course, this may well be an indication that the entire ST program is simply barking up the wrong tree… but isn’t there another possibility?

    Namely, that we simply haven’t developed the appropriate mathematical framework yet..perhaps the breakthrough is just around the corner..

    After all, E. was lucky Riemann had already deveopled non-Euclidean geometry, when general relativity came along. If Riemann hadn’t, and GR involved harder maths, it’s possible physicists might have missed the whole GR thing for quite a while, instead starting with something vague and ambiguous before we narrowing it down…

    or is that simply a naive view of the experimentalist?
    Regards, Cormac

  15. D R Lunsford says:

    Prof R,

    Your point about the mathematical description being more complex is, I think, a little off. In fact most theories become more coherent as they get closer to nature – and this shows up in the mathematical expression. A sure way to know that something is probably on the wrong track is that is lacks tightness and economy of expression. Compare, for instance, the Lorentz deformable electron with Maxwell-Lorentz relativistic dynamics.

    -drl

  16. Walt says:

    Trent, I suggest you scroll up to the masthead, and look where you’re commenting. This is Peter’s blog. If you find his posts repetitive, I suggest you look for something more appealing to you. There are many recipe blogs, for example.

  17. Jason says:

    Hobo is not an offensive term. Hobos call themselves hobos. Hobos are often homeless, but hobo is not synonymous with homeless person. A hobo is simply one who adopts a wandering way of life, traveling by hitching rides on freight trains. There is a hobo convention every August in Britt, Iowa; and a hobo king and queen are cononated there.

  18. AnonLQG says:

    Sara, because Carlo Rovelli rather then Lee Smolin is at the heart of the current developments in Spinfoams/Lattice Gravity/LQG. Smolins latest works are viewed with tremendous skepticism in the community and the general feeling is that he has vastly oversold them. Many are quite unhappy with the fact that he is seen as representing the community.

  19. Professor R says:

    DR, of course I agree with your point ” most theories become more coherent as they get closer to nature – and this shows up in the mathematical expression”.

    But my point is, could it not be that ST simply hasn’t reached this stage yet? Many theories are far too general, and non-specific, in the early stages of development. Perhaps, if the math is difficult enough, a theory could get stuck in this phase for decades before the key breakthroughs occur (if ever)? Just a thought…Cormac

  20. Sara says:

    AnonLQG,
    can you indicate me any papers in which Carlo Rovelli discuss this subject?
    Thank you.

  21. AnonLQG says:

    Which subject?

  22. Arun says:

    One anomaly is that someone from the LQG camp has finally been invited, Carlo Rovelli.

    Don’t worry, string anomaly cancellation will be found in dimensions that do not admit Rovelli.

  23. AnonLQG says:

    is that in and only in? Because as Rovelli is an empirical fact that would mean that anomaly cancellation can not occur for physical systems….

  24. Clark says:

    For a persuasive account of the seminal opposition between Planck and Mach on the core of scientific understanding :

    SEP_on_Ernst_Mach

    One side of the dialectic, in the span of a few generations detached from its founder’s restrained values and amplified to an extreme, inevitably spawns nonsense such as theories of everything.

  25. Yok says:

    > can you indicate me any papers in which Carlo Rovelli discuss this subject?

    “Flipped spinfoam vertex and loop gravity.” Nucl.Phys.B798:251-290,2008. arXiv:0708.1236

    “LQG vertex with finite Immirzi parameter.” Nucl.Phys.B799:136-149,2008. arXiv:0711.0146

  26. Sara says:

    Thank you very much Yok, I’m going to read them with great interest.

  27. Ervin Goldfain says:

    A recent paper by Hashimoto et al. published in Phys Rev D 77, 086001 (2008) claims (what appears to be) the first experimental evidence for brane theory. Here is the abstract:

    “Using holographic QCD based on D4-branes and 8-anti-D8-branes, we have computed couplings of glueballs to light mesons. We describe glueball decay by explicitly calculating its decay widths and branching ratios. Interestingly, while glueballs remain less well understood both theoretically and experimentally, our results are found to be consistent with the experimental data for the scalar glueball candidate f01500. More generally, holographic QCD predicts that decay of any glueball to 40 i is suppressed, and that mixing of the lightest glueball with q  q mesons is small.
    DOI: 10.1103/PhysRevD.77.086001 PACS numbers: 11.25.Tq, 12.39.Mk”

    I invite comments on the validity of these claims.

  28. Peter Woit says:

    Ervin,

    This has nothing at all to do with the debate over the testability of string theory, which is about whether one can test the idea of string theory as a fundamental theory.

    We have very good evidence for what the theory governing strongly interacting particles is: QCD. Many people are working on trying to find string theories that would give approximate calculational methods in QCD valid at strong coupling, and this is one such attempt. If the “predictions” come out right, all that is being tested is the validity of the approximation method.

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