This Week’s Hype

This week’s string theory hype is brought to you by a press release headlined Dark Matter and String Theory? from the Institut Laue-Langevin in Grenoble, and another one from the Vienna University of Technology. These have led to a BBC News report which is getting wide distribution, claiming that Neutrons could test Newton’s gravity and string theory. According to the BBC, this is going to allow a search for:

supersymmetric particles, part of some formulations of string theory that suggest that many extra dimensions exist over tiny length scales, which would require the precision that is only now possible with the team’s approach.

The actual physics here is described in this paper. You’ll need to find an atomic physicist to explain exactly what this is about, but the claim is that the author’s new techniques in resonance spectroscopy can potentially be applied to measuring the gravitational potential at micrometer distance scales. This hasn’t actually been done yet. As for what string theory predicts about how the gravitational potential will deviate from the Newtonian value at these distances, the story is the usual: no predictions at all one way or another. Such violations would be very interesting, but say nothing one way or another about string theory.

Update: The folks at Slashdot have started to get a clue, stripping the nonsense about string theory from this story before posting about it here.

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34 Responses to This Week’s Hype

  1. ucn says:

    Experiments with UCN (ultracold neutrons) have already reached the point where the change in gravitational potential energy of the neutrons makes a detectable change to the de Broglie wavelength of the neutrons. Yes, the neutrons are going so slow that they really do fall down measurably as they traverse a detector! I believe some Berry’s phase experiments have been done but I am not sure of that. So now they can probe gravity down to micrometer length scales? Well done, I say. If the motivation to do this is to test dark matter and string theory, well that’s too bad, but it is good physics in its own right.

  2. Peter Woit says:

    Thanks ucn,

    I am curious if anyone expert in this area can tell whether this really is likely to lead to a method for measuring the gravitational potential at short distance scales, and if so, what the limits on this technique would ultimately be. I don’t see anything in the paper addressing this.

  3. Giotis says:

    When they say:

    “part of some formulations of string theory that suggest that many extra dimensions exist over tiny length scales…”

    they mean most probably the ADD paradigm of large extra dimensions which is not considered part of String theory per se.

    The title is misleading of course but such titles are common practice for the vast majority of journalists; so no surprise there.

  4. Peter Woit says:

    Giotis,

    As I keep pointing out in these cases, the misleading nonsense is not something the journalists came up with. It’s in the press releases given to them, and in the actual Nature paper:

    “The experiments are linked to current ideas in string theories…”

    This can’t be blamed on inept journalists, it’s physicists who are putting this out since they think it will draw more attention to their research.

  5. Giotis says:

    Even so Peter don’t you think there is a big difference between the above excerpt and BBC’s title?

  6. Peter Woit says:

    Giotis,

    If you’re a physicist who decides to participate in issuing a press release with a title making a misleading claim about the relation of your research to string theory, I don’t see how you can complain when a journalist writes a story based on the press release and uses a misleading title involving string theory.

  7. Pawl says:

    I wonder if the physicists approved the title of the press release. (I know journalists don’t generally get to choose their stories’ titles.)

    It might be good for scientists, university and institute press/publicity offices, and media covering science stories to adopt some standards in these matters.

  8. Pingback: La espectroscopía con neutrones ultrafríos permitirá verificar la ley de la gravedad a distancias inferiores a un micrómetro « Francis (th)E mule Science's News

  9. tittle says:

    Curious isn’t it, that everyone can only comment on the title, and nobody can find anything to say about the physics? Has anyone attempted to contact the authors, and/or friends at ILL (say), to ask about the science as opposed to the title?

  10. Bernhard says:

    Anything to do with experiments cannot, by definition, have anything to do with string theory.

  11. Bee says:

    I presently don’t have access to Nature, so have only read the abstract. It sounds related to the experiments with bouncing neutrons in the gravitational field that we discussed on our blog some years back. Yes, one can get down to distances of some micrometers, yet I’m not sure how sensitive one is at this distance to Newton’s law. For that I suppose one would have to actually read the paper. Needless to say, the connection to string theory is vague. Also, if one wanted to test extra-dimensional scenarios with that, those with a lowered Planck scale around a TeV, one would only test d=2 or maybe 3, and these are strongly disfavored by astrophysical measurements already. Details are in the Particle Data Book.

  12. Proudmemberofthecult says:

    One can discuss the phrasing of the press release but it should be obvious that any measurement of a deviation of Newton’s law is indicative of radically new physics beyond what is presently known. If you were writing the press release though you would also put in something about what this would mean. The layman does not know ADD, but does know the word string theory, so this is what they write.

    Big deal.

    Although logically disconnected, any measured deviation *would* strongly favour string theory types of scenario. Even this blog’s owner might agree with that.

    Of course I do not believe they will find anything, but it’s an interesting proposal for which they should get credit.

  13. Bernhard says:

    “Although logically disconnected, any measured deviation *would* strongly favour string theory types of scenario. Even this blog’s owner might agree with that. ”

    This is no way true. Really far from it. It would indicate new physics. There is no way on this Earth this would favour a string scenario. Only if you accept Seiberg’s claim that whatever new thing that appears you call it string theory. This is by the way likely to happen also with whatever new thing we find at the LHC. Somehow it will support string theory, but this is completely dishonest.

  14. Proudmemberofthecult says:

    Dear Bernhard, which other consistent physical theories do you know which support large extra dimensions? That is, theories which do not have a string theory (-inspired) description? Hence the ‘favour’.

    Note it’s the same kind of ‘favour’ which fancies susy solutions to the hierarchy problem. Or inflation as a solution to cosmology problems. For both of these the ‘generic’ mechanism works although figuring out the exact one is beyond current understanding (how many xxxxxx-inflation type models exist, where the x’s are some word?).

    I tried to be careful to say that measuring deviations does not *prove* string theory in any sense, shape or form. Not with the current state of it. It would erect a huge sign in the sky pointing at string theory saying “look here”.

  15. Peter Woit says:

    No, the blog owner doesn’t believe that an observation of a violation of Newton’s law would favor “string theory types of scenario” or “string theory (-inspired) descriptions”. Just because string theory has turned out to be an empty idea you can use to get anything doesn’t mean it’s the thing to turn to if you observe something unexpected.

    I’m somewhat amused by the way string theory partisans have adopted various favored weasel-words. A translation table to keep in mind would be:

    “string theory description”: almost anything
    “string theory-inspired description”: everything else

  16. Proudmemberofthecult says:

    If deviations of Newton’s laws are observed at these scales and no explanation can be found within the known laws of physics, what would *your* explanation be?

    Please note I am being careful with my words because I wanted to avoid being too ‘partisan’… sorry to note I failed.

    - string theory description: arises naturally as a well-defined low energy limit of a string theory setup (modulo all the usual things we do not understand about string theory (time-dependence, non-perturbative behavior, vacuum selection)).

    - string theory-inspired description: incorporates some elements natural in string theory (extra dimensions, supersymmetry, grand unification, etc, etc.), but not all. Usually some form of effective action where the string theory inspiration bit provides some constraint to limit parameter space (usually also rather arbitrarily).

  17. Peter Woit says:

    If evidence is found for new physics at a distance scale of 10^-6 meters, I don’t have any good ideas about what that physics might be. However, in terms of places to start looking, a theory based on new physics appearing at 10^{-35} meters wouldn’t be an obvious place to begin.

  18. Eric says:

    Peter,

    You’ve missed the entire point regarding large extra dimensions in string theory. If the extra dimensions are large, this lowers the string scale so that the new physics appears at larger distance scales than 10^{-35} meters. This is exactly why black holes could be produced at the LHC in models with large extra dimensions.

  19. Zathras says:

    Proudmemberofthecult,

    Care to explain the logical leap between “radically new physics beyond what is presently known” and “which support large extra dimensions?” There’s been a lot of radically new physics done in the past without inventing extra dimensions out of thin air.

  20. Peter Woit says:

    Eric,

    I realize you can make “string theory-inspired” models (such as ADD) with observable effects an any distance scale you want. This doesn’t seem to me a point in their favor. I’m just pointing out that the conventional thing to do when faced with new phenomena at a certain distance scale is start by looking for models where that specific distance scale appears naturally for some reason.

  21. Proudmemberofthecult says:

    Zathras,

    If any deviations from Newton’s law are measured this would be unexpected to say the least. You are right I should have stressed more I’m presuming these measurements would conform to the large extra dimensions scenario. As this is the only known class of physical theories accommodating such deviations in a natural way as far as I know (correct me if I’m wrong!), this is not such a big assumption.

    Hence IF some non-trivial effect is measured it’s a fair bet it will support large extra dimensions. This in turn would favour (not prove) a very specific type of background in string theory.

    Let me stress again that I don’t believe in this scenario, basically for the same reason as Peter W. mentioned. For me though it’s not `natural’ in string theory :). Not ‘natural’ does not mean impossible though: improving bounds by orders of magnitude as is proposed in the press release is a good thing.

  22. Higgs? says:

    Internal Note
    Report number ATL-COM-PHYS-2011-415
    Title Observation of a γγ resonance at a mass in the vicinity of 115 GeV/c2 at ATLAS and its Higgs interpretation
    Author(s) Fang, Y (-) ; Flores Castillo, L R (-) ; Wang, H (-) ; Wu, S L (University of Wisconsin-Madison)
    Imprint 21 Apr 2011. – mult. p.
    Subject category Detectors and Experimental Techniques
    Accelerator/Facility, Experiment CERN LHC ; ATLAS
    Free keywords Diphoton ; Resonance ; EWEAK ; HIGGS ; SUSY ; EXOTICS ; EGAMMA
    Abstract Motivated by the result of the Higgs boson candidates at LEP with a mass of about 115~GeV/c2, the observation given in ATLAS note ATL-COM-PHYS-2010-935 (November 18, 2010) and the publication “Production of isolated Higgs particle at the Large Hadron Collider Physics” (Letters B 683 2010 354-357), we studied the γγ invariant mass distribution over the range of 80 to 150 GeV/c2. With 37.5~pb−1 data from 2010 and 26.0~pb−1 from 2011, we observe a γγ resonance around 115~GeV/c2 with a significance of 4σ. The event rate for this resonance is about thirty times larger than the expectation from Higgs to γγ in the standard model. This channel H→γγ is of great importance because the presence of new heavy particles can enhance strongly both the Higgs production cross section and the decay branching ratio. This large enhancement over the standard model rate implies that the present result is the first definitive observation of physics beyond the standard model. Exciting new physics, including new particles, may be expected to be found in the very near future.

    See: http://cdsweb.cern.ch/record/1346326?

  23. Brathmore says:

    Peter,

    Quick questions from someone who is not a physicist but enjoys reading this blog: What is the state of the experimental evidence saying that gravity is quantized? Is the BBC correct when it says that in 2002, “gravity’s quantum nature was proven”? How strong is this evidence? (I had thought– perhaps erroneously–that the quest to find a quantum theory of gravity was motivated largely by theoretical concerns).

    Thanks

  24. Peter Woit says:

    Higgs?

    That looks very, very interesting! It looks like one can’t yet get a copy of the paper without a CERN login. If anyone can provide this or more information, that would be great.

  25. McNicholl says:

    After a quick read of the article: a sensitive resonance measurement of the energy levels of slow neutrons due to the gravitation potential from the earth (among other boundary interactions). The results agree at the current level of precision with a classical treatment of the gravitational potential. The authors propose to improve precision with a technique analogous to a well known resonant technique (separated oscillatory fields). Now I am not a theoretician so up to you guys but, for what it is worth: (1) this is not a high precision measurement of graviation per se–the precision is required due to the small mass of the neutrons; (2) much of the misleading hype (not sure how much due to the paper itself) comes from the misleading juxtaposition of the words “quantum states” and gravitation; (3) though the vertical (transverse) dimensional scale of the experiment is ~ 20 microns, one is not measuring graviational effects between two objects of this scale ( a la Cavendish balls)–one of the objects is indeed the earth.

  26. Peter Woit says:

    Brathmore,

    What’s observed is the effect of the classical gravitational potential on the wavefunction of a particle. This isn’t really “quantum gravity”, by which one normally means quantization of the gravitational degrees of freedom (e.g. the metric), which would show up as new phenomena such as a graviton (quantized excitation of the gravitational field). If this method works out, you would get more information about classical gravity at shorter distances, but still nothing about whether and how gravity gets quantized.

  27. McNicholl says:

    Still questionable that it provides information on classical gravity at small scales…if I intrpet scale as the range we are always inverting. I.e., the effective range we know from 101 is ~ radius of the earth.

  28. Arun says:

    Assuming Higgs? is not spoofing us:
    http://arxiv.org/abs/1103.0631

    Quoting from the abstract: “…the di-photon Higgs signal $pp->h->\gamma\gamma$ is a sensitive probe for new physics…….(i) In the MSSM the signal rate for the SM-like Higgs boson (the lightest CP-even Higgs boson) is suppressed compared to the SM prediction, and for many survived parameter samples the suppression can be over one order; (ii) For the SM-like Higgs boson in the NMSSM the signal rate can be either suppressed or enhanced by one order, depending on the parameter space; (iii) For the SM-like Higgs boson in the nMSSM the signal rate is much suppressed.”

  29. OhDear says:

    “Higgs?” more information please…

    Why are only a few authors listed, and not the whole collaboration? Also I wouldn’t expect the abstract of an experimental paper to gush about new physics like that. So I’m a little sceptical and think you might be pulling our collective leg.

  30. Amos says:

    @OhDear:

    Re “Why are only a few authors listed”? That seems to be how Atlas organizes its papers. See http://www-wisconsin.cern.ch/physics/papers.html .

    And its the right names. But it still doesn’t feel right.

  31. Anonymous (but PW can see my details anyway) says:

    Higgs? is not pulling any leg, the paper is there. Of course the reason there are only few authors and such a strong claim is the same – it’s still an internal publication. And there seems to be some room for discussion about the photon identification methods, but after all that’s why internal notes are internal.

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