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Higgs field popular descriptions

  1. Jul 16, 2012 #1
    With the recent announcement at Cern there have been many video clips published describing the Higgs field. They show heavy and light particles passing through a field and the commentary says that the effect of the field is to slow down particles and thus give them mass. The Higgs field supposedly permeates empty space. As we know particles travelling through empty space continue with constant velocity and momentum. The Higgs field description suggests that particles travelling through the Higgs field are slowed so the more they travel through the Higgs field the more they should be slowed down. The Higgs field theory seems to be inconsistent with observation. Can anyone explain?

    Regards
    WaveHarmony
     
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  3. Jul 16, 2012 #2

    Drakkith

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    How is it inconsistent with observations?
     
  4. Jul 16, 2012 #3
    Well, the popular descriptions suggest that the Higgs field slows down particles. Particles in empty space will continue in a state of uniform motion without being slowed.
    WaveHarmony
     
  5. Jul 16, 2012 #4

    Bill_K

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    WaveHarmony, The Higgs field is (partially) responsible for particle masses, but the popular description that it "slows them down" is quite misleading. Especially, it does not mean that they get slower and slower and eventually come to a stop, like traveling through a jar of molasses!
     
  6. Jul 17, 2012 #5
    yeah, I think Physicists need to 'dumb it down' for the layman to help explain their mathematics and particle observations.
     
  7. Jul 17, 2012 #6
    I can be easily explained by saying that the Higgs field couples to the particle's acceleration. A particle indeed is being slowed down, but the opposing force is proportional to its acceleration.
     
  8. Jul 17, 2012 #7

    Drakkith

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    This is much harder than one might think. Things almost always get lost in the analogies. How would anyone describe the interaction of subatomic particles with a field when your target audience doesn't even know what a subatomic particle is. Or what an atom is for that matter. Or what a field means in science.

    It's comparable to me explaining a championship winning play in american football when you've never even seen a game before and I'm not allowed to explain the basic rules first.
     
  9. Jul 17, 2012 #8

    Drakkith

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    But you cannot word it like this, it is incorrect. The particle is not being "slowed down", that is a reduction in velocity. It has resistance to acceleration, which we already have a term for, inertia, which is interconnected to mass.

    This is exactly the case I was referring to in my above post. It's much more difficult than one might think to correctly describe theories in science without using scientific vocabulary and math. The Balloon Analogy for cosmology is another perfect example.
     
  10. Jul 17, 2012 #9
    Who is the target audience really? I have trouble understanding it, because I don't have the graduate mathematics to know the notations. All these shows that on youtube, news or Nova are interesting, but really, what are they trying to accomplish? I think it is only to gain public interest the best they can, considering the huge money investment in the LHC. The search for the Higgs boson (or lack of) is really only one step anyway as it doesn't get the full picture of explaining things.
     
  11. Jul 18, 2012 #10
    The problem is compounded by the fact that I thought I understood the nature of mass as described by general relativity. I am happy with the explanation of the observed properties of mass in terms of spacetime curvature. The mass of the Earth curves spacetime so the moon responds to the spacetime curvature and follows its orbit. GR explains that any object with mass curves spacetime and the effect is cummulative. So electrons protons and neutrons curve spacetime. It seems to me that this explanation of the nature of mass is very clear and the only missing piece of the puzzle is 'how does an electron curve spacetime?' The Higgs field description doesn't seem to help with this aspect of the problem.

    Can anyone explain to me in clear unambiguous terms how a Higgs field gives mass?
    WaveHarmony
     
  12. Jul 18, 2012 #11

    Drakkith

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    The shows have nothing to do with the LHC itself, it is purely entertainment for people who like science. Yes, entertainment. I read all kinds of stuff on science just because I enjoy it. The side benefit is that I also learn general knowledge.

    The higgs is a quantum theory, not a theory on gravitation. I believe you could say that the higgs explains inertial mass while relativity explains gravitational mass if you want to separate mass like that. But I'm really not sure.
     
  13. Jul 18, 2012 #12
    The Higgs has two responsibilities - to give mass to the force carriers of the weak force, and to give mass to the fermions. Let's start with the first.

    The weak force is mediated by three massive particles, called the W+, W-, and Z bosons. One important aspect of the Standard Model is electroweak symmetry - at a sufficiently high temperature (at a time immediately after the big bang), the weak force becomes indiscernible from the electromagnetic force. Of course, this means that the W and Z bosons were massless. Breaking this symmetry is the job of the Higgs. Spin 1 particles like the W and Z bosons have at least two degrees of freedom. One way a massless particle could gain mass is by the absorption of a scalar (spin 0) particle as it's longitudinal mode (as it's second degree of freedom). A scalar particle that does this is called a Nambu-Goldstone boson. Originally, the Higgs had four degrees of freedom - H+, H-, H0, and h. The thing about the first three is that they are equivalent to the longitudinal modes of W and Z bosons. So, they played the role of Goldstone bosons, and they were absorbed (or 'eaten' as it's often described) by the W and Z bosons, becoming their second degree of freedom, giving them mass.

    This leaves us with one degree of freedom for the Higgs, h. This ends up being the scalar Higgs boson, the quantum of the Higgs field. Now, the Higgs field takes a constant value at every point in space - called the vacuum expectation value. Through Yukawa coupling, fermions interact with this vacuum expectation value (in terms if Feynman diagrams, you can think of a particle as interacting with the VEV at various vertices). By interacting with the VEV they attain mass, determined by the exact value of the VEV.

    Note that, of course, this is a simplified explanation that leaves out more explicit details.
     
  14. Jul 20, 2012 #13
    That's not quite accurate, though, is it? One thing it seems to me about the term "unification" when used in the electroweak context is that it glosses over the fact that, prior to symmetry breaking, there are still two distinct forces: weak isospin (the Ws) and weak hypercharge (the B field), and these have different coupling constants. The theory describes how electromagnetism (the A field) and the Z then come about after symmetry breaking as orthogonal mixtures of W0 and B, with the Z also eating the H0.

    Prior to symmetry breaking, there is no electromagnetic force as such. There are the W and B forces. The latter would behave just as electromagnetism does now, except it would be a bit stronger, but is separate.
     
  15. Jul 20, 2012 #14
    Yes, you're correct - that's why I posted that last sentence, that I omitted many technical details for clarity.

    The Higgs mechanism breaks the electroweak symmetry [itex] SU(2) X U(1)_{Y} [/itex] to [itex] U(1)_{em} [/itex]. The generator of [itex] U(1)_{em} [/itex], Q, is given by [tex] Q = \frac {Y} {2} + I_{3} [/tex] Where Y is the weak hypercharge, and I3 is a component of the weak isospin. As you mention, this symmetry breaking mixes W0 and B0 to produce the photon and the Z, by [tex] \begin{pmatrix} \gamma \\ Z^{0} \end{pmatrix} = \begin{pmatrix} cos \theta_{w} & sin \theta_{w} \\ -sin \theta_{w} & cos \theta_{w} \end{pmatrix} \begin{pmatrix} B^{0} \\ W^{0} \end{pmatrix} [/tex] Thanks for pointing that out.
     
    Last edited: Jul 20, 2012
  16. Jul 21, 2012 #15
    Thank you very much for your explanation. I can't form a clear picture of the meaning of the descriptions but this is my lack of understanding of the fundamental concepts of the standard model. The big disappointment for me is that the concept of mass which is so nearly fully explained by General Relativity is treated in a completely different way in particle physics with no apparent link between the concepts involved.

    Does anyone else feel that physics is in need of a conceptual revitalisation to provide a single unified picture of everything?

    WaveHarmony
     
  17. Jul 21, 2012 #16
    How is mass fully explained in General Relativity?
     
  18. Jul 22, 2012 #17
    We experience mass in our everyday lives and in experiments in two forms: gravitational mass and inertial mass. General relativity explains that a mass distribution has the effect of curving spacetime. GR also indicates that the effect of mass in curving spacetime is cummulative so that the greater the mass the greater the spacetime curvature. Mass also responds to spacetime curvature resulting in objects with mass seeking to move closer together. This so called gravitational force is really due to the objects seeking a lower energy. (Actually all so called fundamental forces can be treated as a search for a lower energy state).

    Einstein also showed that there is an equivalence between an object in a curved spacetime environment (so called gravitational field) and an object under uniform acceleration indicating an equivalence between inertial and gravitational mass. So my claim is that GR fully explains the property we observe as mass with the one missing point that GR does not explain how mass curves spacetime. We can assume that the way mass curves spacetime is consistent so that electrons neutrons and protons which have mass do indeed curve spacetime in a similar way. So if we could explain how the electron curves spacetime then we would have a full explanation of the property mass.

    WaveHarmony
     
  19. Jul 22, 2012 #18

    Drakkith

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    Waveharmony, I could be wrong, but I don't believe the higgs is in any way related to general relativity. It is fully a quantum theory and has nothing to do with gravitation. General relativity explains that stress-energy curves spacetime, and since mass has energy it will do so as well.
     
  20. Jul 22, 2012 #19
    So, how does GR explain the fact that the mass of the electron is 511 keV/c2?
     
  21. Jul 22, 2012 #20
    WaveHarmony - general relativity has nothing to do with the Higgs mechanism. The Higgs mechanism explains why particles have mass. General relativity explains why (macroscopic) massive objects gravitate.
     
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