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Can string theory predict faster than light neutrinos ?

  1. Sep 27, 2011 #1
    Can string theory or quantum gravity theory predict faster than light neutrinos ?
     
    Last edited: Sep 27, 2011
  2. jcsd
  3. Sep 27, 2011 #2

    atyy

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  4. Sep 28, 2011 #3

    MathematicalPhysicist

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    They publish articles faster than mushrooms spreading on a tree.
     
  5. Sep 28, 2011 #4
    Ok , In the paper the author said that neutrinos can explore regions where the value of h is slightly larger than 1 . Where are these regions ? are they on the surface of D-brane or in the bulk geometry outside?Also if neutrinos are open strings then they can't escape to the extra dimensions they will be confined to the brane.Does the author talk about randall sandurm theory in this paper . I do not know much in string theory so explanation of these matters will be useful .
     
  6. Sep 28, 2011 #5

    haushofer

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    And cite each other faster than the speed of light.
     
  7. Sep 28, 2011 #6
    Of course it can, ST can predict everything
     
  8. Sep 28, 2011 #7

    Demystifier

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    If so, then why string theorists do not like loop quantum gravity, which is also predicted by string theory? :biggrin:
     
  9. Sep 28, 2011 #8

    Haelfix

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    Every theorist in the world has tried to come up with a method to make the Opera result work, and had to revisit basic assumptions about the nature of reality. This is quite fun, even though it is a completely tortured process, whereby the theorist has to bend over backwards.

    If you actually had read the paper, you would know that embedding/UV completing such an extra dimension model (the EFT) into String theory is extremely difficult, b/c it violates the Null Energy condition. Read, it just doesn't seem to work.

    Many of us have come to similar conclusion for different but related reasons, even at the level of the effective field theories. You either have to introduce an enormous amount of finetuning, and a whole superstructure to enforce that things work out properly, or you run afoul of basic experimental facts and start having theoretical breakdowns.

    (I wrote down a model that ended up having an unstable vacuum at 3 GeV to give you an idea of the sorts of issues). The fun fact that you end up learning is that exact Lorentz invariance and universal couplings really protects you from disaster in hundreds of different ways.

    One of the many fundamental problems any such theory faces is that neutrinos and leptons are linked, and so explaining why one doesn't feel the effect, and the other does, invariably leads you to write down a new model for electroweak symmetry breaking. This is bad, b/c we already know a lot about that, and the constraints are more or less extreme.
     
  10. Sep 28, 2011 #9
    A nice answer; what a wisdom. So: what kind of model do we have to built if (a) no Higgs and (b) neutrinos with a small mass and a speed over that of the photon? More generally where and how can one present or propose a (toy) model to professionnals?
     
  11. Sep 28, 2011 #10
    Stumbled across this page, which suggests that one solution for superluminal neutrinos via string theory is that neutrinos can under some circumstances escape the brane and move in the bulk (as gravitons do). This paper and this follow up were cited-- there appears to be nothing special about these papers, they just appear to be the two articles that could be dug up where someone made a model with neutrinos that escape in the bulk. If I'm understanding this right the neutrinos in this model are NOT superluminal, instead the reason for allowing neutrino escape was to "explain" the lack of right handed neutrinos in the observable universe (they all fled out into the bulk). I do not know if this is the same kind of model discussed in the paper atyy links.
     
  12. Sep 28, 2011 #11

    Haelfix

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    Again, the fundamental problem with most types of Opera ideas is twofold

    1) You need to have a very sharp energy dependance in the dispersion relationships to explain the Supernovae measurement. This is doable in the extra dimension models, whereby only past a certain scale do the neutrino's 'feel' the extra metric structure.

    2) You need to explain why in the standard model, each family of lepton doublets (say the electron and the electron neutrino) do NOT react similarly to the changing geometry. This is the key point where most ideas hit a wall (and not so much in the actual spontaneous breaking of Lorentz invariance perse). Simply put, we know the electron doesn't move past the speed of light with extreme precision. So you need to explain this experimental asymmetry somehow. Of course this goes right to the heart of electroweak symmetry breaking, and really requires changing the universality of the couplings. This is where problems lurk for those aforementioned papers, whether for string theory or really any phenomenology.

    To give an analogy, it would be like if you measured an apple falling upwards in an experiment and were asked to figure out a plausible explanation. You could come up with all sorts of ideas whereby another force breaks the inertial frame (say a fan on the ground blowing air upwards), or even modifying Newtons laws perse (more drastic). But you would get stuck rapidly if in addition the experiment tested every other particle, and those didn't fall upwards (Eg apples, and only apples fell upwards).
     
    Last edited: Sep 28, 2011
  13. Sep 28, 2011 #12

    marcus

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    Thanks for giving your opinion on this! I think your second post may have some shared viewpoints with what Andreas Weiler said in NewSci as quoted by N.E.W. I'll get both so we can compare.

    http://www.math.columbia.edu/~woit/wordpress/?p=3996
    This Week’s Hype
    Posted on September 28, 2011 by woit
    ==quote N.E.W.==
    It had to happen. New Scientist managed to find a physicist willing to describe the OPERA result as “evidence for string theory”:

    So if OPERA’s results hold up, they could provide support for the existence of sterile neutrinos, extra dimensions and perhaps string theory. Such theories could also explain why gravity is so weak compared with the other fundamental forces. The theoretical particles that mediate gravity, known as gravitons, may also be closed loops of string that leak off into the bulk. “If, in the end, nobody sees anything wrong and other people reproduce OPERA’s results, then I think it’s evidence for string theory, in that string theory is what makes extra dimensions credible in the first place,” Weiler says.
    ===endquote===

    It seems to me that both your hypothetical* explanation and that of Andreas Weiler involve assuming large extra dimensions so that our world is immersed in a bulk, out into which particles can under some circumstances "leak" or whose geometry (as you put it) certain ones of them may be able to "feel".

    *if the results hold up, then how to make that explainable within string context.
     
    Last edited: Sep 28, 2011
  14. Sep 28, 2011 #13

    marcus

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    I checked some outward signs to see who Andreas Weiler is. I think I'd say HEP phenomenologist, who has co-authored highly cited papers, quite a few 100+.
    http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=a+Weiler%2C+Andreas&FORMAT=WWW&SEQUENCE=citecount%28d%29 [Broken]
    Born 1975. PhD 2005. He is now permanent/faculty at DESY Hamburg, I think. He has been at good places: Munich, CERN, Cornell. His most recent paper, that I can find, was posted August 2011.

    http://arxiv.org/abs/1108.1183
    If no Higgs then what?
    Adam Falkowski, Christophe Grojean, Anna Kaminska, Stefan Pokorski, Andreas Weiler
    (Submitted on 4 Aug 2011)
    In the absence of a Higgs boson, the perturbative description of the Standard Model ceases to make sense above a TeV. Heavy spin-1 fields coupled to W and Z bosons can extend the validity of the theory up to higher scales. We carefully identify regions of parameter space where a minimal addition - a single spin-1 custodial SU(2) triplet resonance - allows one to retain perturbative control in all channels. Elastic scattering of longitudinal W and Z bosons alone seems to permit a very large cut-off beyond the Naive Dimensional Analysis expectation. We find however that including scattering of the spin-1 resonances then leads to an earlier onset of strong coupling. Most importantly for LHC searches, we define a self-consistent set-up with a well-defined range of validity without recourse to unitarization schemes whose physical meaning is obscure. We discuss the LHC phenomenology and the discovery reach for these electroweak resonances and mention the possibility of a nightmare scenario with no Higgs nor resonance within the LHC reach. Finally, we discuss the effects of parity breaking in the heavy resonance sector which reduces the contributions to the S parameter.
    34 pages, 10 figures

    He describes himself as HEP theorist
    http://www.desy.de/~aweiler/Home.html [Broken]
    But his interests seem closely tied to what can be found out using LHC and what immediate changes in Standard Model might result. He does not seem, from his 26 co-authored papers, to be in any sense a string theorist.
     
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  15. Sep 28, 2011 #14

    Haelfix

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    Actually I don't agree with Andreas. I don't see any consistent theory or explanation of the data at the moment other than the rejection of the hypothesis. Not from string theory, not from effective field theory, not from anywhere.

    So absent any plausible model (so far none exist), I can't 'say' that the data favors anything.

    Obviously if 2 or 3 other experiments confirm the result, then an extra dimension model might be a good research path, but then embedding the result into string theory would probably be the last thing on my mind at that point. Step 1000, in a long road, so to speak.
     
  16. Sep 29, 2011 #15
    Indeed so, like so many who say nonsensible things about string theory. Other recent example: Gordy Kane a string physicist neither, which does not prevent him to write high-visibilty articles full of nonsense. And ouf course this is then eagerly exploited by the Woit at al's to suggest that string physicist are typically like that. Sigh.
     
  17. Sep 29, 2011 #16

    marcus

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    Ooops! The Weiler in question is TOM Weiler at Vanderbilt U. in Tennessee. Not Andreas.

    Sorry about that! It is Tom Weiler that you don't agree with.
     
    Last edited: Sep 29, 2011
  18. Sep 29, 2011 #17

    marcus

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    I think an important thing to notice about T. J. Weiler is that currently he is not involved with string theory at all. His work seems mainly in astrophysics.
    http://www.hep.vanderbilt.edu/~weilertj/

    In his description of his research interests I see primarily neutrino astrophysics, with also some interest in cosmic ray astro.
    He has 86 papers on arxiv including recent co-authorship with Lawrence Krauss also with Robert Scherrer, and other people whose names ring a bell.

    Of the 86 papers, 78 are in hep-ph, that is in phenomenology.

    When I look down his webpage describing his research interests (and his research group at Vanderbilt) I see nothing at all about string. It is all astroparticle, cosmology, etc.

    However going back to 2006 I see this rather speculative short paper about neutrinos possibly taking "shortcuts in large extra dimensions".
    http://arxiv.org/abs/hep-ph/0611263
    Shortcuts in extra dimensions and neutrino physics
    Heinrich Päs (Alabama), Sandip Pakvasa (Hawaii), Thomas J. Weiler (Vanderbilt)
    (Submitted on 20 Nov 2006)
    We discuss the possibility of sterile neutrinos taking shortcuts in extra dimensions, and the consequences for neutrino oscillations. This effect influences the active-sterile neutrino mixing and provides a possibility to accommodate the LSND evidence for neutrino oscillations together with bounds from accelerator and reactor experiments. We briefly comment on causality in such schemes.
    Comments: 4 pages, 3 figures, talk presented by H. Paes at SUSY06, UC Irvine

    and a followup 2007 paper
    http://arxiv.org/abs/0710.2524
    Neutrino time travel
    James Dent, Heinrich Päs, Sandip Pakvasa, Thomas J. Weiler
    (Submitted on 12 Oct 2007 (v1), last revised 9 Dec 2007 (this version, v2))
    We discuss causality properties of extra-dimensional theories allowing for effectively superluminal bulk shortcuts. Such shortcuts for sterile neutrinos have been discussed as a solution to the puzzling LSND and MiniBooNE neutrino oscillation results. We focus here on the sub-category of asymmetrically warped brane spacetimes and argue that scenarios with two extra dimensions may allow for timelike curves which can be closed via paths in the extra-dimensional bulk. In principle sterile neutrinos propagating in the extra dimension may be manipulated in a way to test the chronology protection conjecture experimentally.
    Comments: 4 pages, 2 figures. Submitted for the SUSY07 proceedings

    On closer inspection I also found these more recent papers:
    http://arxiv.org/abs/0906.0150
    Baseline-dependent neutrino oscillations with extra-dimensional shortcuts
    Sebastian Hollenberg, Octavian Micu, Heinrich Päs, Thomas J. Weiler


    http://arxiv.org/abs/0908.3986
    Explaining LSND using extra-dimensional shortcuts
    Sebastian Hollenberg, Octavian Micu, Heinrich Päs, Thomas J. Weiler
     
    Last edited: Sep 29, 2011
  19. Sep 29, 2011 #18

    atyy

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    What are the constraints like on muons compared to electrons? Are those less tight? Could you make just the muon and muon neutrino break light speed, but not the electron and electron neutrino?
     
  20. Sep 29, 2011 #19

    Haelfix

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    I do not know the current experimental bounds on the speed of propagation of the Muon.

    You would have to redo the analysis of this beautiful paper:
    arXiv:hep-ph/0209264

    For electrons, we know that they obey Lorentz invariance up to at least 100 TeV, through a combination of Supernovae measurement (from eg the Crab Nebula) as well as the absence of the vacuum Cerenkov effect. Thus you are looking at a hard to explain difference of at least 10^4 between electron neutrinos and electrons.

    Honestly, imposing a family asymmetry in the propogation speed, in addition to the electroweak one, makes things worse, not better. For one thing, I suspect that such a thing would already have shown up in existing neutrino oscillation experiments as a violent departure from expectations. I'd have to work out the exact physics...
     
  21. Oct 3, 2011 #20
    If Higgs boson is not detected at LHC , Could it signal a mechanism of electroweak symmetry breaking by extradimensional models regarding also that extradimensions could explain OPERA results without violating relativity?
     
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