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Qestions on concept of mass

  1. May 4, 2010 #1
    Mass is the amount of matter in an object. Or at least that's the classical definition. But there are particles of matter that don't have mass. How is that possible if it's a particle of matter? Plus how can the theoretical Higgs give "stuff" to matter if the matt er is matter and therefore has matter in them?
  2. jcsd
  3. May 5, 2010 #2
    no that is wrong, in classical mechanics mass is a measure of inertia and how it respond to gravity, thus we have mass_inertia and mass_gravity (Einstein showed that they are equal)

    Thus a good popular description of the Higgs mechanism is that inertia at quantum level is due to the particles "swimming" in the pool of higgs, thus makes them go slower than without higgs -> they cannot move at speed of light c anymore and thus are massive.

    Another example is a famous person entering a room with many people, they will gather around him and make it hard for him to move at fast pace. But if I entered that room- no one would care and I could go faster then the famous person.

    So, your mistake was the classical definition of mass.
  4. May 5, 2010 #3
    Ok but as for the massless particles are they not affected by the theoretical Higgs field?
  5. May 5, 2010 #4
  6. May 5, 2010 #5


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    The U(1)*SU(2) theory is constructed such that the coupling of the Higgs vev to one gauge boson (which is identified with the photon) vanishes; therefore by construction the photon is exactly massless.

    The so-called Yukawa couplings of the Higgs to the fermions (electron, ... neutrinos, ..., quarks, ...) is arbitrary, that means it must be adjusted according to the experimental data.
  7. May 22, 2010 #6
    Regardless of mass or "masslessness", I want to ask if it is not fair to say that at the level of quanta, we can conceptualize replusion, wobble, spin, even pressures, as the result of particle collisions, but that without a clear understanding or concept of a medium of some kind, the fact is we really don't know what attraction is about at any level? Is this what is driving the various brane theories, this quest for a "Sea of Higgs" - is this what we are after? a "medium" to explain attraction? Other than the joy of looking at a really elegant single equation, Is this the root of the search for a unified field theory? Hope you find the question attractive.
  8. May 22, 2010 #7
    I was always wondering, if 'massive' particle is at rest, what is a source of its gravitational field?

    massive particle has mass=0, and its mass is an illusion because it couples with Higgs field. Without having quantum gravity, can we use some kind of semi-classical approach and tell what components of stress-enegry tensor are non-zero in such case?
  9. May 22, 2010 #8


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    This is confusing. Are you suggesting that objects must be moving in order to gravitate? Anything with energy gravitates, even particles at rest.
  10. May 22, 2010 #9
    "An isolated non-spinning solid object moving at a constant speed will not radiate."

    I am not a physicist, I don't have the name that goes with this quote, I believe we are in the process of sending spacecraft billions of miles apart to attempt to resolve the question: Is "gravitating" a form of "radiating"? I would like to be pushed toward some reference material on this thread. Thanks
  11. May 22, 2010 #10


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    No. Gravitating and radiating (in the context that you are quoting) are very different things. I don't have time to elaborate now, but I will check back. Perhaps in the meantime someone else can help out...
  12. May 23, 2010 #11
    massive particle has mass = 0

    that is a contradiction... were you drunk when you wrote this? ;)
  13. May 23, 2010 #12

    No we are looking if there IS gravitation radiation - not if gravity is a FORM of radiation...

    compare with electromagnetism and electromagnetic waves.
  14. May 23, 2010 #13

  15. May 23, 2010 #14
    No, I am Russian so vodka does not affect my reasoning :)
    As I understand there are no massive particles
    All particles have rest mass = 0
    Higgs mechanism gives an illusion that they are 'massive'
    So what we call 'mass' of massive particle is just a effect of the Higgs condensate on the truly massless particle
  16. May 23, 2010 #15
    1) protons have mass without the Higgs mechanism

    2) it is just not an illusion, the Higgs mechanism GIVES mass to particles.
  17. May 23, 2010 #16
    1. Most of it is "relativistic" mass of bound system, as quarks are very light
    2. If it GIVES mass then without Higgs particles are massless. Hence, they are Fundamentally massless (for example, at very high temperatures when Higgs mechanism does not work).
  18. May 23, 2010 #17
    1. that doesn't matter from a graviational point of view

    2. They have mass without higgs particles ;) but not without the higgs field. And in all high energy/temperature limits the effect of rest mass vanish ...

    so a massive particle at rest has mass and thus it has a stress energy tensor
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