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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.
     
  22. Jul 22, 2012 #21
    Wave:
    that's an objective, for sure, but hasn't been achieved yet. The Higgs fields, so many of them I can't keep track, attempt to provide a mechanism for mass....But like many other components of the standard model, these Higgs fields are manual insertions individually tailored with the specific properties needed to provide different particles with the observed mass. A nice interim step, but hardly a comphrehensive theory.

    I happen to be reading right now Alan Guth's 'The Inflationary Universe' and he discusses a few Higgs fields in Chapter 10/11. As an example, three Higgs fields are used to describe [construct] magnetic monopoles. So Guth talks about how he tried to avoid the magnetic monopole problem in a theory of inflation, that is, the fact that there could be many, but we observe none. How do we avoid them?

    He realized if he could delay a phase transition in inflationary expansion#, horizons would increase in size and magnetic monopoles would disappear....be smeared out of existence, hence his reliance on a Higgs field with a false [temporary] vacuum...the old 'Mexican hat' energy density profile.

    Sidney Coleman's 1977 paper THE FATE OF THE FALSE VACUUM describes "The process by which the Higgs fields of the false vacuum can tunnel thorugh the energy barrier..and Coleman's work was a big help to Guth.

    Voila: when you know the physical characteristics required, you can invent mathematics to produce them and glue them into whatever model you'd like. It's not like all this stuff is available via first principles. How could Higgs fields, if they exist at all[+], not be related to gravity when both a related to mass.....but that link apparently remains a mystery as already noted in a prior post.

    # Guth points out what he thought he 'discovered' about inflation turned out to be in a 1925 Lemaitre paper from MIT that he knew nothing about....the de Sitter solution to Einstein's field equations....but apparently Guth coined the term INFLATION as part of his research.

    + I am referring to the existence of multiple Higgs fields not whatever might have be identifiey at CERN....
     
    Last edited: Jul 22, 2012
  23. Jul 26, 2012 #22
    I agree that General Relativity doesn't predict the mass of the electron but it is the nature of the property mass that I am trying to focus on. If we perform a measurement of mass by experiment we are measuring the inertial or gravitational mass and the underlying theory that applies to these measurements is general relativity. So what we experience as mass is described by GR.

    From a GR perspective when asked how does an electron curve spacetime we would naturally look to the structure of the electron for an explanation rather than an external agency such as a Higgs field that gives it mass.

    The fundamental theories of physics seem to operate in their own separate compartments. General Relativity, the standard model, quantum theory, string theory all seem to have a different underlying world view. For the standard model, the elecron is an elementary particle so we don't ask about its structure. In quantum theory (copenhagen interpretation) the electron doesn't exist between emission and observation. String theory would describe the electron as a string but without any explanation of what a string is made of.

    Each theory has grown up from mathematical models which correlate with observation and experiment but there does seem to be a need for fundamental examination of basic physics to develop a coherent physical world view in a top down way rather than starting from the maths. The theories are clearly correct in their own sphere of applicability but there is a need for unification.
    WaveHarmony
     
  24. Jul 26, 2012 #23
    Higgs field can explain time dilation near light speed C?
    It is Relativity theory area?
     
    Last edited: Jul 26, 2012
  25. Jul 26, 2012 #24
    No, it has no relevance to special relativity. Lorentz transformations occur to preserve a constant speed of light in all inertial frames of reference.
     
  26. Jul 28, 2012 #25
    In trying to understand the nature of mass and starting from the question 'How does an electron curve spacetime?' there is another area of physical theory which seems relevant. The relationship between the energy and frequency E=hf where E is the energy equivalent of the mass and h is planks constant. This frequency relates to the wave character of the electron as evidenced by interference experiments. This emphasises the wave character of the electron as opposed to the particle character emphasised in the standard model.

    If the electron is considered as a wavelike object in spacetime this would seem to fit better with the GR viewpoint than the Higgs field hypothesis.

    WaveHarmony
     
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