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Only four fundamental forces in the universe?

  1. Nov 16, 2003 #1
    Are we being very naive to think that there are only four fundamental forces in the universe? I mean after all the Greeks thought that there were only four elements in the universe. How do we expect to know for sure that unification involves only those four forces?
     
  2. jcsd
  3. Nov 16, 2003 #2
    Re: Unification?

    We work with what we know. We can hardly unify forces that we don't know about. (Although it could potentially happen that, in the process of unifying the four interactions we know about, we find that the mathematics requires a the existence of a new interaction in order to consistently unify the other four.)
     
  4. Nov 17, 2003 #3
    How does the Higgs Boson fit in (if they ever find it)? If this is finally discovered, which force will it carry?
     
  5. Nov 17, 2003 #4
    The Higgs boson is required to explain why the particles that mediate the weak nuclear force - the W and Z - are so massive. The extraordinarily high masses of these particles are mathematically inconsistent with the Standard model, so particle physicists postulated the existence of another particle (or particles): the Higgs boson.

    Folks at the LEP collider at CERN in Switzerland found tracks that were consistent with the Higgs boson, but couldn't also rule out that these came from other particles. Until the Large Hadron Collider is completed, experiments are continuing at Fermilab in the USA.

    Jess
     
  6. Nov 17, 2003 #5

    chroot

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    Actually, the Higgs field (and concomitant Higgs boson) are the mechanism responsible for giving all particles mass, not just the weak bosons.

    The reason the weak bosons are massive is very simple -- it is because the weak force is very short-ranged. This might be a chicken-before-the-egg situation, of course, since you could just as well argue that the weak force is short-ranged because the weak bosons are massive.

    - Warren
     
  7. Nov 17, 2003 #6
    Thanks for that guys, but if the Higgs boson is real and gives mass the property it has, it must carry a force that is felt by some particles and not by others.
    Which of the four forces is this?
     
  8. Nov 17, 2003 #7

    selfAdjoint

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    Your conclusion is incorrect. The Higgs does not carry a force. The way it gives some particles mass and not others is technical (translation: I don't know how to explain it). But the Higgs interacts in a different way than a force carrying boson.

    The key test is the Z particle and the photon, which are sort of like Arnold Schwartzeneggar and Danny DeVito in Twins. I wish someone would post on just how one of them gets mass and the other not, and not just by handwaving about "broken symmetry". How does it break? And both of them are mixtures of other particles; how does that work too? If you have to start in LaTex let it be, then maybe others can get it down to words.
     
  9. Nov 17, 2003 #8

    chroot

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  10. Nov 17, 2003 #9
    Higgs

    Hi all,

    I don't have the quantum math that is probably involved, but perhaps someone could enlighten me about the following line of thought:

    1.The Higgs field/partical is proposed to explain the short range of forces between quarks, (weak force), but requires a very high mass coefficient to do so. Correction?

    2.The concept of mass is beginning to break down at the quark scale, as is shown by the fact that the proposed masses of quarks do not add up to the masses of the particals they form. Correction?

    3.Below the scale of nuclear particals (protons and neutrons) extradimensional effects begin to predominate, allowing the conservation laws (symetries) to appear to be broken, as virtual particals, quantum tunneling, and time reversals become common, altho statistically they cancel out at larger scales, thus preserving the physical laws observed on the human scale. Comments?

    4.Given the above, and the uncertainties of measurement at the quantum scale, we are reduced to raw speculation about processes that occur at the sub-nuclear scale. The best we can hope for is an internally consistant model which predicts the statistical behavior of particals and forces we actually observe. Comments?

    5.I have been playing with a toy model multiverse idea which I believe may be promising as a candidate for an internally consistant model which will predict observed statistical behaviors. It isn't a theory, exactly, but I would like the opportunity to present it in an intellectually challenging environment, such as this forum. Perhaps more experienced forum members will forward some advice in this regard.

    Thanks,

    Richard T. Harbaugh
     
  11. Nov 17, 2003 #10

    chroot

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    Re: Higgs

    The Higgs mechanism does one, and only one thing: imbue particles (all of them) with mass.
    It's quite difficult to establish distinct masses for quarks, due to the fact that they cannot be isolated. The "extra mass" is just the binding energy of the system. It is not a "breakdown" of anything.
    The various symmetries (C, P, and T, for example) have nothing to do with extra dimensions. They are the quantum-mechanical versions of classical symmetries in which things in the universe operate similarly at all times and places in the universe. In the microscopic domain, there is no well-defined notion of thermodynamics (since thermodynamics is statistical), and thus there is no well-defined notion of a "forward arrow of time." In any event, extra dimensions have nothing to do with it. The theories, such as string theory, that involve extra dimensions have made no predictions which are testable with existing technology.
    "Raw speculation?" Are you kidding? We have a theory, the Standard Model, which explains to high precision every experiment we are currently capable of performing, and many more that we should soon be able to perform. We know there are inconsistencies when masses are large and sizes are small, and thus the theory is incomplete -- but certainly no one is engaging in "raw speculation."
    You are welcome to post your theory in our Theory Development forum, accessible under the General Physics forum.

    - Warren
     
  12. Nov 17, 2003 #11
    what does all that have to do with my question?
     
  13. Nov 17, 2003 #12
    raw speculation

    It does seem from your reply that it would be premature to post any models, since my choice of words has ellicited a critical response. That is, of course, what I was looking for and I thank you for it.

    Is it appropriate to carry on a conversation about the above in this forum? I will presume so until notified otherwise.

    You said:
    "The Higgs mechanism does one, and only one thing: imbue particles (all of them) with mass."

    So does this contradict something in my statement? I will not pick on the side issue of the proposed existance of massless particals at this time.

    You said:
    "It's quite difficult to establish distinct masses for quarks, due to the fact that they cannot be isolated. The "extra mass" is just the binding energy of the system. It is not a "breakdown" of anything."

    Thank you for challenging my use of the term "breakdown". I am slightly familiar with the mass-energy equivalence. I am puzzled, though, by an explanation of mass that involves proposing that the W and Z particals, many of which might be supposed to inhabit a hydrogen atom, are many times heavier than the atom itself. If there is a large amount of energy present, why does it not reveal itself as mass when we measure the mass of the hydrogen?

    You said:
    "The theories, such as string theory, that involve extra dimensions have made no predictions which are testable with existing technology."

    Yes, you have revealed my "secret," which is that I am actually interested in sting theory, which, I think, may never be measurable, altho the existance of macroscopic objects which exhibit what may be quantum behaviors (I am thinking of BEC and C_60 here) may give us some windows by way of analogy to sub-microscopic systems. By the way, I have studied microbiology at university and some people may have issue with the use of the word "microscopic" to describe processes occuring at sub-nuclear scales. We have, as yet, no microscope capable of seeing objects smaller than atoms, as far as I have heard.

    The purpose of my model, which I have spent some years on (in my spare time) is to make such predictions which are testable with existing technology, or at least to make predictions which are in line with existing observations.

    You said:

    "We know there are inconsistencies when masses are large and sizes are small, and thus the theory is incomplete -- but certainly no one is engaging in "raw speculation."

    Thanks for your reaction. I didn't mean to touch on any sore points with my choice of words. My self-critical features have taken a fancy to those words but I am not bound by them. However, surely you will agree that the whole Higgs theory is pretty speculative. Even the standard model is open to questions. What is the significance of the observed families and generations of particals? I hope to be able to show some correspondence between my rather simple model and the stability of observed quanta of matter, including mass numbers. But I am still a long way off from a coherent theory, and so I am looking for the exact kind of criticizm you offer. Thanks!

    Richard T. Harbaugh
     
  14. Nov 17, 2003 #13

    chroot

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    Re: raw speculation

    Anytime! Welcome to physicsforums.
    The only kinds of discussion which must be conducted only in the Theory Development forum are the kind that begin with "I believe existing theory is wrong. My theory is that..."
    Sorry for nitpicking. You said the Higgs mechanism can be used to explain the short-range nature of nuclear forces, but it doesn't do that directly. The short-range nature of nuclear forces is understood to be a result of the large masses of the gauge bosons. In an indirect way, their coupling to the Higgs field is therefore the reason why the nuclear forces are so short-ranged. Even if the Higgs mechanism turns out to be wrong however, the short-range nature of the nuclear forces will still be understood simply as a consequence of the bosons' mass -- we simply won't know why they have such masses.
    Because the force-carrying particles are virtual. They exist fleetingly, in accordance with the uncertainty principle, borrowing energy from the vacuum for a short time. The total energy (and thus mass) of the system is constant -- a virtual particle in a system does not alter the system's mass.
    We have many such microscopes. They go by names like Tevatron and LHC.
    I welcome you to post your ideas in the Theory Development forum for discussion.
    It is speculative, but not because the theory is not sound. It is possible that any theory, despite being very plausible, just isn't correct. We haven't done enough experiments yet to rule it out, and it is on good theoretical footing -- so we'll keep it around for now.
    Hence your quote, "who ordered that?!"
    If your theory can explain the masses of the known particles, people will take notice -- even if it's just a black box mathematical machine whose gears even you do not fully understand.

    - Warren
     
  15. Nov 17, 2003 #14
    I'm not entirely sure what is relevant and what isn't, but it has certainly made for an interesting thread!

    Chroot - thanks for the link to the Higgs Boson explanations - excellent.
     
  16. Nov 17, 2003 #15
    This has been fun, thanks all. one last note, perhaps to be taken up again later:

    "We have many such microscopes. They go by names like Tevatron and LHC."

    I am very interested in these "microscopes", but my understanding is that they work by examining reactions which occur at some time and distance from the event of interest. As such, though there are lots of tracks and so on to measure, we have to use a lot of inference about what the tracks represent. I may be old fashioned, but my idea of a microscope is of something where I can gaze into the big end and get a visual glimpse of something going on at the small end. Atom smashers give us lots and lots of valuable information (most of which filters down to us amatures as conclusions, not as evidence) but they do not give a picture in the sense of "scope," which seems to me to be an optical property. Anyway I am open to correction on this minor sidelight.

    Thanks,

    Richard T. Harbaugh
     
  17. Nov 17, 2003 #16

    chroot

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  18. Nov 17, 2003 #17

    chroot

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    This is indeed quite old-fashioned. Electron microscopes certainly don't work this way, and they're ubiquitous. Even more advanced is x-ray crystallography, which doesn't involve anything even resembling "vision." And beyond that, we have particle accelerators. They are microscopes, for certain -- their function is to allow us to determine the small details of something, and that's what a microscope does.

    - Warren
     
  19. Nov 17, 2003 #18
    gauge symmetry is broken whenever you have a scalar field with some VEV (vacuum expectation value).

    the Higgs is proposed to be this field. the Higgs must carry weak isospin and hypercharge if it is to break SU(2), and hypercharge, if it is to break U(1). it should also be neutral, because we like our long range EM forces.
     
  20. Nov 17, 2003 #19

    selfAdjoint

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    Okay on the VEV, I think. Makes the vacuum not symmetric?

    I have a question about isospin and hypercharge. Unless I am mistaken these are just metaphors for quark content. Spin "up" is having more u quarks than d quarks, and spin "down" is the reverse. And hypercharge is just baryonness + strangeness, where the first is +1 or -1 (antiparticles) if the particle contains three quarks and 0 otherwise, and strangeness is +1 or -1 if the particle contains an s quark and 0 otherwise. Right? Or I guess you could say it labels representations of SU(3), but I'm not as clear on that as I'd like to be.
     
  21. Nov 17, 2003 #20
    well, i require that the Higgs be a scalar field, in order that the vacuum is symmetric. any field in a nontrivial rep of the lorentz group cannot have a VEV, for it would violate isotropy of the vacuum.


    i was talking about weak isospin, which labels not the quark content, but the weak isospin content. leptons have these quantum numbers as well as quarks.

    for example, the neutrino has +1 weak isospin, and the electron has -1. neither has any quarks.

    and hypercharge has nothing to do with baryonness either. its just another gauge group that a particle can be charged under. there are three: SU(3), SU(2), and U(1). which rep of SU(3) you are in tells you the color of the state, which irrep of SU(2) tells you the weak isospin, and U(1) tells you the hypercharge.

    the strong isospin symmetry (which is only an approximate symmetry. only the strong force respects this symmetry), is true basically because you can change flavors without changing color, and all asymptotic states are color singlets, i.e. transform trivially under SU(3), i.e. there are no free colored states.
     
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