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nLab > Latest Changes: fundamental particle

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    • CommentRowNumber1.
    • CommentAuthorUrs
    • CommentTimeMar 27th 2025

    added pointer to:

    • David Griffiths: Introduction to Elementary Particles 2nd ed., Wiley-VCH (2008) [[pdf] (https://www.physics.utah.edu/~belz/phys5110/Griffiths.pdf), pdf, Wikipedia entry]

    diff, v10, current

    • CommentRowNumber2.
    • CommentAuthorDmitri Pavlov
    • CommentTimeMar 27th 2025

    What is the difference between a “fundamental particle” and a “particle”? The current version of this article doesn’t explain what a fundamental particle is.

    diff, v11, current

    • CommentRowNumber3.
    • CommentAuthorUrs
    • CommentTimeMar 27th 2025

    A fundamental or elementary particle is one that is not a bound state of other particles, hence which is “indivisible”. So electrons and quarks are elementary, but protons and nuclei are not.

    Yeah, the entry should say something. It’s just a stub waiting for somebody to do something.

    • CommentRowNumber4.
    • CommentAuthorUrs
    • CommentTimeMar 27th 2025
    • (edited Mar 27th 2025)

    Okay, I have written some paragraphs, just off the cuff:

    In physics, by a fundamental or elementary particle one means a particle which is not a bound state of other objects, hence which is “indivisible”.

    In computational practice this means that elementary particles are those that are really point-like, while non-elementary particles have a finite extension (if only in some averaged sense).

    In the standard model of particle physics elementary particles include among the fermions the electrons and quarks, and among the bosons the photon and the Higgs boson. In contrast, all hadrons, hence all baryons, hence in particular the proton and neutron, are bound states of quarks, and then all nuclei are bound states of protons and neutrons, and all atoms are bound states of nuclei and electrons.

    But of course, “atoms” get their name from a time when they were thought to be indivisible elementary particles, which highlights that the notion of what counts as “elementary” can change over time.

    Various “beyond standard” models postulate that at least some of the currently understood elementary particles are in fact not so. For instance in “composite Higgs models” such as in technicolor models, the Higgs boson (which appears to be an elementary particle according to available measurements) is postulated to be a bound state and hence non-elementary.

    In a slightly different manner, in usual string theory phenomenology none of the currently observed elementary particles would in fact be elementary, but all of them would arise as massless “states of strings”.

    diff, v12, current

    • CommentRowNumber5.
    • CommentAuthorperezl.alonso
    • CommentTimeMar 27th 2025

    Wait, are technicolor models still alive in practice? In what way?

    • CommentRowNumber6.
    • CommentAuthorUrs
    • CommentTimeMar 27th 2025

    Indeed they are not. But they are examples of models such that, and so forth.

    I don’t think my lines say otherwise, but feel free to edit if you find it necessary.

1 to 6 of 6

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