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Very special relativity?

  1. Jan 24, 2007 #1
    http://arxiv.org/PS_cache/hep-ph/pdf/0601/0601236.pdf

    Anyone seen this?:-

    You'll probablly have to read the PDF to get a good view as the layout get's a bit mangled by the forum.

    Here's the source paper, sounds interesting if a little speculative? Thoughts?Praise? condemnation, sneering indignation?

    edited for length - please only post a brief portion of the article and allow people to download themselves. Thanks.
     
    Last edited by a moderator: Jan 28, 2007
  2. jcsd
  3. Jan 24, 2007 #2
    Ok sorry I was in a hurry before, essentially what this rather laborius and scientific paper is saying, or more correctly what the two of them are saying, is that in certain cases Special relativity may be broken, For example they postulate since Neutrinos have only left spin and only massless particles have single directional spin, they suggest Neutrinos are peculiar in some way. And may actually be able to travel faster than light, justification for this is simply that we can never see right handed spin because of the speed they travel at. It's a rather tenuous proposition and it relies on just the right mass to make a point that maybe in this instance the underpinning law that nothing can travel as fast as light with mass, may just be innacurate. Anyway. Sorry for not putting an explanitory on it, but my Bus was waiting.
     
    Last edited: Jan 25, 2007
  4. Jan 26, 2007 #3
    I read this article in last weeks (20/1/07) Newscientist titled Einstein’s Nemesis – the flaw in space-time that could wreck relativity.

    It’s from scientists with credibility (Nobel prizewinner Sheldon Glashow and colleague Andrew Cohen), and they do make a valid point that special relativity needs a fix to explain neutrino observations.
    All observed neutrinos have left-handedness – they spin to the left – anticlockwise - as they approach you. But only massless particles can be one-handed, because of the rules associated with relativity. And it is now known that neutrinos have mass and so cannot travel at the speed of light. Therefore, it’s possible to have a reference frame that moves faster than the approaching neutrino. And an observer in an inertial frame overtaking a neutrino would see the back of it as he approached, and would see it spinning to the right. So some neutrinos should have right-handedness, but none are observed. So they give space-time a directional component to compensate, effectively ruling out the possibility of a right handed observation being possible.

    It was an interesting article, but not the nemesis I expected.
     
  5. Jan 26, 2007 #4

    Garth

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    One significant (IMHO) fact that is often forgotten is that SR is only completely valid for the ideal situation of a space-time in which the components of the Riemannian are all zero, i.e. no curvature.

    However, all the observations we make today are made either in the Earth's gravitational field, or that of the Sun (by spacecraft in deep space such as Pioneer) or, in future, that of the galaxy and cosmos at large, where the presence of matter, stress and energy cause at least some of the Riemannian components to be non-zero.

    Such space-time has matter in it, and the presence of matter allows a particular frame of reference to be identified, that which co-moves with the Centre of Mass/Momentum. A Machian argument might be that the Principle of Relativity does not hold in such an environment and that in the real universe SR is inappropriate, except as an approximation limit.

    Thus fact that neutrinos are only observed left handed, even though they do not travel at the speed of light, might simply be evidence that in the presence of matter the Principle of Relativity breaks down, not that in the absence of matter SR breaks down.

    In other words the New Scientist article may be describing the Nemesis of the foundations of GR, not SR.

    Garth
     
    Last edited: Jan 26, 2007
  6. Jan 28, 2007 #5
    I agree, it's a bit overly speculative a bit like MWI, but let's not go there. :rofl:

    Reading the actual paper, is like standing in a loft with musak playing dull; it's interesting, but it's making too many leaps of logic.
     
  7. Jan 28, 2007 #6

    Gokul43201

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    Such as what?

    I would hardly knock a paper by (unarguably) one the the greatest physicists of the century unless I've at least understood every single argument made in it.
     
  8. Jan 28, 2007 #7

    JesseM

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    What is thought to be the main source of neutrinos we observe--stars, cosmic rays, what? Perhaps the asymmetry could be explained in terms of the sources typically not moving at relativistic velocities relative to us, and typically emitting the neutrinos at high velocities relative to the source?
     
  9. Jan 29, 2007 #8
    Why does mass and only one spin lead to the conclusion that something can travel faster than the speed of light? A resort to authority is not really a valid argument, Newton was wrong about the Nature of light. Just because he's a Nobel prize winner doesn't mean everything he says from that point on is true.

    And I do understand what he's saying if you don't think I do what do you think the summary of the paper was based on, moonbeams and fairies? :wink: :tongue::smile:

    Anyway what I think is not really important I wanted to see what others thought.
     
    Last edited: Jan 29, 2007
  10. Jan 29, 2007 #9
    To know one's ignorance is the best part of knowedge - Lao Tzu
     
  11. Jan 29, 2007 #10
    Ok I'm an idiot, now we've established that may we proceed :smile:
     
  12. Jan 31, 2007 #11
    I must admit I'm a little dissapointed, I'd kind of hoped someone sould shed a bit more light on this, but I guess people just agree they are right.:approve:
     
  13. Jan 31, 2007 #12

    jtbell

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    More likely, nobody here knows enough about the subject and has read the paper in enough detail to be able to comment intelligently on it.
     
  14. Feb 1, 2007 #13
    Or that :smile: I asked someone in the know and he said? How did he figure that? Bloody cynics:tongue2: :rolleyes: :biggrin:

    In his opinion it could just be that we haven't detected bosons with right spin because there aren't any full stop, anyway since this is easy enough to prove in experimentation I'll reserve judgement as I'm way to untutored to really understand what's behind this. :smile: although to be frank after reading the NS article, I have a pretty good idea even if I don't know the math.

    Interesting though

    http://www.newscientist.com/channel/fundamentals/mg19325871.400-sending-einstein-into-a-spin.html

    Dummed down for laymen:-:smile:

     
    Last edited: Feb 1, 2007
  15. Feb 1, 2007 #14

    Garth

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    As I implied in my post #4 above, perhaps it is GR that needs 'fixing up' not SR. :wink:

    Garth
     
  16. Feb 1, 2007 #15

    jtbell

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    Neutrinos from beta decay of nuclei typically have energies of a few MeV. If I remember correctly, neutrino oscillations indicate a mass in the ballpark of a few eV, which gives a relativistic [itex]\gamma[/itex] on the order of a million, which corresponds to a speed of about 0.9999999999995c, or better, [itex](1 - 0.5 \times 10^{-12})c[/itex]. In order to "flip" the helicity of a neutrino, it seems to me that an observer would have to be moving at least that fast relative to the source.

    Off the top of my head, I can't think of any processes that produce lower-energy neutrinos. Then there's the little problem of detecting them! :bugeye:
     
  17. Feb 1, 2007 #16
    What I'm having trouble understanding though is why this leads to the conclusion that there is VSR? Could it not just be that we cannot detect them because they travel at .9999999999995c? Mind you it sounds like we won't have to wait long for an answer.:smile:
     
  18. Feb 1, 2007 #17

    jtbell

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    Here's how I understand the situation...

    By the nature of the weak interaction as we know it, neutrinos must be produced with left-handed helicity (and antineutrinos with right-handed helicity). If neutrinos were massless, then they would maintain that helicity according to all observers, because it would be impossible to travel faster than a neutrino and thereby reverse the direction of its velocity (and its helicity) from your point of view.

    But neutrino oscillations indicate that neutrinos do have mass, so why don't we see right-handed neutrinos or left-handed antineutrinos?

    One possibility is that such neutrinos can indeed exist in principle, but it's simply not practical to produce or observe them. That was the point I was trying to make with my calculation.

    Another possibility is that such neutrinos are forbidden by some mechanism (other than masslessness which doesn't apply), which is what Glashow and Cohen seem to be proposing with VSR.

    If in fact there is no practical way to produce or detect "wrong-helicity" neutrinos, then their apparent absence can't be used as evidence for VSR, just as an initial motivation for it. If VSR can predict other phenomena that are experimentally testable, then it would definitely be interesting to carry out those experiments! But until such experiments are done, all we can say about VSR is that it's an interesting idea.
     
  19. Feb 1, 2007 #18

    Nice expanation, thanks.
     
  20. Feb 4, 2007 #19
    Since relativity is a macroscopic theory and not quantum mechanical in itself, it seems justified to search for departures from it at the microscopic level. Neutrino mass may very well serve as one departure point.
     
  21. Feb 5, 2007 #20

    JesseM

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    But all the known quantum field theories, like quantum electrodynamics and quantum chromodynamics, obey special relativity (they have Lorentz-symmetry).
     
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