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Prediction of Lepton mass

  1. Oct 11, 2008 #1
    Do we have prediction of Lepton mass (Electron, muon, tau) from any “Theory of everything” ?

    The string theory is here for decades. If string theory is truly a “theory of everything”, the Lepton mass should be predicted all ready.

    what is the status to this issue ?
  2. jcsd
  3. Oct 12, 2008 #2
    Koide formula
  4. Oct 12, 2008 #3
    The string theory predict the Koide formula from basic principles?

    Not only is this result odd in that three apparently random numbers should give a simple fraction, but also that Q is exactly halfway between the two extremes of 1/3 and 1.
    This result has never been explained nor understood.

    We expect from the "Theory of Everything" to explained the Koide formula

    Frankly speaking we expect to have all the arbitrary parameters of the standard model to be explained from first principle
  5. Jan 3, 2009 #4
    I just realized that the koide formula allows for the possibility of a fourth lepton of mass zero. I know that it used to be believed that the electron had no mass and that this belief was indeed based on some kind of experimental evidence. I wonder what the experiment was?
  6. Jan 3, 2009 #5

    Vanadium 50

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    It was never believed that electrons had no mass. The electron discovery is usually credited to J.J. Thomson, who first measured q/m for the electron. So from the point of its discovery, it was known to be massive.
  7. Jan 3, 2009 #6
    somebody believed it. I remember reading about it. but I cant remember where. maybe someday it will come to me.
  8. Jan 3, 2009 #7

    Vanadium 50

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    As you might expect, that's not a terribly compelling reference.

    Do we agree that before the electron was discovered it doesn't make any sense to talk about its mass? And do we agree that after the electron was discovered it was known to have mass? If you agree with those statements, you have to believe the logical conclusion that there was never a time when electrons were thought to be massless.
  9. Jan 3, 2009 #8
    who are you arguing with??

    I said that I once read something where someone said the electron was massless. I asked if anyone knew anything about it or the experiment that they referred to.
  10. Jan 3, 2009 #9

    Vanadium 50

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    You said more than that - you said there was experimental evidence for this. For the reasons I gave, I do not believe that what you said is correct.
  11. Jan 3, 2009 #10


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    The OT mentioned leptons in general. Perhaps you mixed up the electron with the neutrinos? which were originally believed to be massless. In the original "standard model" neutrions were assumed massless, but now there are indications that they might have have mass, although a tiny one. But the fundamental understanding of the origin of neutrino masses is on the list of open problems in physics, as well as the other parameters of the standard model.

    String theory seems so far to rather than reduce the number of free parameters, increase them.

  12. May 22, 2009 #11
    the idea was that the mass of the electron could be explained purely by its self inductance (if its electric field extended far enough down). so it was thought to be massless but at the same time it wasnt thought to be massless.

    but I retract any suggestion that a massless charged particle might actually exist. I far as I know that would not be allowed by quantum mechanics.

    I distinctly remember reading a book which said that the result of an experiment, which it described in detail, was that the electron showed no mass beyond its self inductance. now the book may have been wrong but I know what I read. I just cant remember what book it was.
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