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What is charge? Why do fundamental particles possess it?

  1. Mar 26, 2008 #1
    I attended a colloquium a few days ago concerning the LHC and the search for the Higgs Boson. After some thought, I have the following question.

    Among other things, there are two measurable properties of all of the fundamental particles in the Standard Model: mass and charge. It is hypothesized that a particle gets its mass by interacting with the Higgs field (colloquially, by the tendancy of local vacuum to 'cling' to it as it moves through space).

    But what gives a particle its electric charge?

    Is this a meaningful question? Is it by some interaction with some charge field - by interaction with the local EM field? No, for charge generates a local EM field, right? Is my question off the wall, unresearched, or being currently discussed? Is it only meaningful by way of discussing gauge theories? Essentially, what is charge, and why do some particles have it and others don't?
     
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  3. Mar 26, 2008 #2

    arivero

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    There are really two different question: 1) Why does a preserved quantity such as electric charge exist? and 2) Why is it quantized?
     
  4. Mar 26, 2008 #3
    It's one of the fundamental forces of nature [electric charge], it's a phenomenon we take for granted. People should be able to explain why [what happens] when one charged particle is attracted to another one, but to break it down further than that is not really known.

    Not really sure if I am answering your question though...
     
  5. Mar 26, 2008 #4
    ...meaning we should just consider it as a conserved quantity of a system, similar to energy, momentum, etc. From that point of view, why is it considered special, and not just a dynamical symmetry? Because it is quantized and its greater applicability?

    It would seem to me that mass would hold that status, too. That it is a fundamental property of nature, and that it's origin cannot be probed further - but that's seemingly incorrect. I guess why one can be probed further and the other not is the nature of my confusion.
     
    Last edited: Mar 26, 2008
  6. Mar 26, 2008 #5

    Yeah gravity is also a fundamental force in nature, and it hasn't been probed further yet. Gravitational forces and electrical forces share similar mathematical properties, so uncanny that scientists are intriqued to find out why they behave in similar fashions. That is more getting into string theory though:

    http://en.wikipedia.org/wiki/String_theory



    But honestly I am still a little fuzzy on what you are asking?
     
  7. Mar 26, 2008 #6

    tiny-tim

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    … t3 + Y … ?

    Is it fundamental … isn't it hypercharge plus t3?
     
  8. Mar 26, 2008 #7
    Consider the Standard model (say, as it appears on the Wiki article http://en.wikipedia.org/wiki/Standard_Model). Each particle is listed in the left-most column, and to the right are listed the currently known values of its various observables (electric charge, weak isospin, weak hypercharge, color charge, mass).

    So the positron has electric charge +1 and mass 511 keV.

    A month ago, I would have thought it strange to ask, "Why does the positron have a mass of 511 keV?" Today, a particle physicist would likely answer, "Because it interacts with the Higgs field in such a way as to give it a 'mass' of 511 keV." That is, the positron's mass is defined by the strength of its interaction with the Higgs field.

    My question is exactly this, "Why does the positron (or any other fundamental particle) have the charge it has." Is it because it interacts with some field that gives it its charge? This seems to me like a perfectly reasonable question that follows from our new understanding of mass and the Higgs field.
     
  9. Mar 27, 2008 #8
    Yes why ?
    The yukawa coupling between higgs and fermions do not look really quantized.
    Why electric charge is ? And why is it such that it cancels prefectly eg anomalies ?
    Can it be explained in GUT theories ?
     
  10. Mar 27, 2008 #9

    pam

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    Charge (electric, weak or color) follows from the principle of Local Gauge Invariance (LGI) in quantum mechanics. If it is desired that the phase of a spinor wave function psi have no physical effect, then vector fields must be introduced with a psibar V psi interaction.
    Why LGI is needed, and why e^2=1/137 are deeper questions.
     
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