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Higgs Mechanism and Gravity

  1. Sep 8, 2014 #1
    I understand that Higgs mechanism “gives” mass to particles in QM sense. My first question is, why it also gives mass in GR sense, bending space-time? Of course, I don’t expect an answer now as it is definitely a TOE/Quantum gravity territory. However, let me rephrase my question in a narrower sense.

    Are there any constraints that guarantee that any invariant mass in QM sense is also a mass in GR sense? What if, say, only Higgs mechanism gives “GR” mass, and neutrinos (as I understand their masses are not explained by Higgs?), while they have tiny mass in QM sense don’t bend space-time at all (even they have to react to gravity, so their path thru space-time curves like light)

    Invariant mass is not conserved, so such QM-but-not-GR mass should not lead to bad paradoxes?
     
  2. jcsd
  3. Sep 8, 2014 #2

    Demystifier

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    Not really. The Higgs mechanism is classical in essence.

    Concerning your main question, there is a general principle called equivalence principle which guarantees that any mass obtained in a classical manner will also have gravitational manifestations.
     
  4. Sep 8, 2014 #3
    Makes sense.
    However, as I understand, experimental support of equivalence principle doesn't include neutrinos (for obvious reasons), so all these experiments prove the equivalence principle for Higgs-given mass only?
     
  5. Sep 8, 2014 #4

    Demystifier

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    Experiments which test equivalence principle do not see a difference between masses obtained by Higgs mechanism and those obtained by other means. Besides, equivalence principle is valid even for massless particles such as photons.
     
  6. Sep 8, 2014 #5

    ohwilleke

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    1. Mass in the QM sense is also always mass-energy in the GR sense, although the reverse is not true.

    2. The rest mass of a particle in the QM sense can be extrapolated to determine special relativistic momentum at a velocity of a given fraction of the speed of light.

    3. The Higgs mechanism gives rise to fundamental particle rest masses in the Standard Model. It is emphatically not the only source of GR mass.

    4. GR mass-energy that goes into the stress-energy tensor in GR is a broader concept that does not distinguish between mass and energy (converting according to E=mc^2). GR mass-energy includes, for example, (1) pure energy (e.g. in a photon) contained in a particle with zero rest mass, (2) the mass of a hadron (i.e. a composite particle made of quarks bound by gluons such as protons and neutrons) that arises from strong force interactions of gluons between quarks that dwarfs the rest mass of the fundamental particles themselves rather than the Higgs mechanism, and (3) the mass-energy of a neutrino's combined rest mass and kinetic energy (often relativistic and many times the neutrino's rest mass).

    5. The only form of mass or energy that is treated specially in GR from the point of view of the form of the equations is gravitational field energy (a technical issue discussed in the "Do Gravity Gravitate" thread right now at the GR forum at physics forum https://www.physicsforums.com/showthread.php?t=768604). This is a quite tricky issue.

    6. Neutrinos bend space-time, just as any other clump of mass-energy does, in GR and since they have a non-zero rest mass are not light photons. They could get their mass from the Higgs mechanism like any other fundamental particle (Dirac mass), or they might get their mass from another mechanism (e.g. the see-saw mechanism). The lambda CDM model of cosmology assumes that neutrinos have mass and that in the aggregate this has a gravitational impact on the way that the universe evolves and makes predictions about the sum of the neutrino mass eigenstates based upon observation that are in accord with nuclear physics measurements.

    7. The equivalence principle applies to neutrinos.
     
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