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Neutrino mass paper

  1. Dec 26, 2014 #1

    PeterDonis

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    I just came across this paper arguing that the electron neutrino may have negative mass squared:

    http://arxiv.org/abs/1408.2804

    It says it has been accepted for publication. I'm wondering if anyone has seen it and can comment on the paper's arguments.
     
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  3. Dec 26, 2014 #2

    ShayanJ

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    Weren't tachyons only instabilities in fields and not actual particles?
     
  4. Dec 26, 2014 #3

    Vanadium 50

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    I don't see where it has been accepted. If a referee, I would probably not accept it. There's very little new here - Ehrlich has been going on about this for more than a decade.

    It is absolutely true that the neutrino mass experiments that measure m-squared allow it to go negative in their fits. To do otherwise biases the result high. It is also true that these measurements come out negative - the PDG average is -0.6 +/- 1.9 and the statement "Given troubling systematics which result in improbably negative estimators of m2 in many experiments we use only Kraus 05 and Lobashev 99 (I think they mean Aseev 11) for our average." They then go on to comment on exactly how these two measurements are better than the ones they supersede and how the systematics are better controlled.

    As for the cosmological measurements, I am not at all surprised that if one replaces constants in the calculation that the results shift, nor that with the right set, the mass squared can go negative. However, what I don't see is a good argument that these are the right constants to use, apart from the fact that they give interesting conclusions.

    For me to believe neutrinos are tachyons, I would prefer to see one strong piece of evidence rather than a lot of weak ones.
     
  5. Dec 26, 2014 #4
    Existence of Tachyons is not yet established. But If it establish it would be actual particles with imaginary mass energy and negative time. Further they will loss energy with increase in time.
     
  6. Dec 26, 2014 #5

    http://phys.org/news/2014-12-faster-than-light-particles.html

    This article is mentioning it to be accepted in journal Astroparticle Physics http://www.journals.elsevier.com/astroparticle-physics/

    However On Journal Webpage It is not there
     
  7. Dec 26, 2014 #6

    ChrisVer

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    For me negative neutrino masses squared would be a disaster, because then what kind of cosmological contribution would one have?...So indeed systematic errors can play important role in determining the value.
     
  8. Dec 26, 2014 #7

    ShayanJ

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    I read it here:
    (From this page.)
     
  9. Dec 26, 2014 #8
    check this part of your link containing details http://en.wikipedia.org/wiki/Tachyon#Fields_with_imaginary_mass
    It is for field whose uncondensed states are tachyons but after tachyonic condensation they become positive squared mass.
    But its only one case which is partially tachyonic as final excitations are not tachyons, only intermediate are. Even Higgs Boson has imaginary mass in uncondensed phase
    Tachyons is rather general term whether possible or not, but include excitation which would actually travel faster than light
     
  10. Dec 26, 2014 #9

    mfb

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    The paper talks about a decay chain p->n->p->n->... for high-energetic particles. Do they want to violate special relativity? Otherwise I don't think that makes sense.
    I don't see enough evidence to introduce negative squared masses and violations of special relativity just to get better fits to current experimental data. It does not help to have 6 measurements consistent with the proposed negative value - they also have to be completely inconsistent with positive values to make the model interesting.
     
  11. Dec 26, 2014 #10

    Vanadium 50

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    Yes.
     
  12. Dec 26, 2014 #11

    PeterDonis

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  13. Dec 26, 2014 #12

    PeterDonis

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    This was my sense after skimming the paper, that it was giving multiple very weak pieces of evidence but no strong evidence (AFAIK no strong evidence exists of neutrinos, or any other particles, being tachyons). Thanks for the confirmation. :)
     
  14. Dec 26, 2014 #13

    mfb

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    Then they need really strong evidence. Especially in a field where 2-3 sigma effects come and go all the time and even 5 sigma effects can disappear.
     
  15. Dec 26, 2014 #14

    ShayanJ

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    Thanks for that. But this only treats scalar tachyons which isn't useful when we talk about neutrinos. I checked some QFT texts but non of them treat tachyons(which isn't surprising). Not much was on internet too. Can you suggest a text that treats tachyons?(Specially fermionic ones)
     
  16. Dec 26, 2014 #15

    PeterDonis

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    The original paper by Bilaniuk and Sudarshan (referenced in the article) turns out to be available online:

    https://www.uam.es/personal_pdi/ciencias/jcuevas/Teaching/Taquiones.pdf

    It doesn't explicitly discuss solutions of equations of motion the way the Usenet article does; however, the considerations raised in the paper appear to me to apply to any tachyonic particle, regardless of spin.

    Google shows a number of articles that appear to discuss tachyonic solutions of the Dirac equation. AFAIK the general solution properties of the Klein-Gordon equation that are discussed in the Usenet article should also hold for the Dirac and Maxwell equations, since both of those are known to be consistent with relativistic causality.
     
  17. Dec 26, 2014 #16

    ShayanJ

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    But I think whether or not the following sentence is true, depends to a high extent on the equation that the particle obeys. This is the main reason I ask for further references. Or its a general thing not depending much on spin?
     
  18. Dec 26, 2014 #17

    PeterDonis

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    I don't have a reference, as I said, but I'm curious why you think this would depend to a high extent on the equation of motion. The Dirac and Maxwell equations share a lot of properties with the Klein-Gordon equation, including, as I mentioned, consistency with relativistic causality. Indeed, multiplying the Dirac equation by its complex conjugate gives you the Klein-Gordon equation (this is one way of expressing the fact that two fermions with opposite spins can form a zero-spin bound state). So I'm not sure why you would expect a drastic difference in the behavior of tachyonic solutions to these equations.
     
  19. Dec 27, 2014 #18

    Matterwave

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    If neutrinos are Tachyons, wouldn't the neutrinos from SN1987A have arrived here much earlier? Is this addressed in the paper? My internet connection is very poor, and loading it is taking some time lol.
     
  20. Dec 27, 2014 #19

    PeterDonis

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    Not if their energy was large enough for their velocity to be sufficiently close to the speed of light. (Of course, that "sufficiently close" might be a problem--I haven't run the numbers to see if the required energy would be compatible with what was detected.)

    Not as far as I can see.
     
  21. Dec 27, 2014 #20

    Matterwave

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    From what I know of neutrinos from SN1987A, the fact that they arrived ~3 hours ahead of the light means their speed is bound very close to the speed of light. It originated from the LMC I believe, so it has been traveling to us for ~150,000 years... that they arrived only 3 hours early limits their speed to c to one part in a billion.
     
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