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Question about strong force

  1. Oct 13, 2012 #1
    Reading about the strong force and the residual strong force I'm a bit confused about the interaction. Largely it keeps mentioning it the result of particle exchange and mentions that it has infinite distance, but that the residual strong force doesn't have infinite distance. However, it doesn't really explain that well. Why is that? Is the residual strong force something like Van der Waals effects within hadrons?

    Also if it is a particle interaction does that mean it occurs only between two particles at once in a highly dynamic manner (switching between all those around it)? Or is the residual strong force a field force like EM or gravity? Just much steeper cutoff.

    Also any good particle physics books?
    Last edited: Oct 13, 2012
  2. jcsd
  3. Oct 13, 2012 #2
    Reading up on Quantum Chromodynamics may give you the answers you want. Also Yang-Mills Quantum Field Theory.
  4. Oct 14, 2012 #3
    Yes. To make the analogy more explicit, we could say that even though atoms are electrically neutral, the "residual electromagnetic force" can bind them together into molecules. But this residual force falls off quite quickly. The usual Coulomb force falls off like 1/r^2, but the residual attraction falls off like 1/r^6 (I think). Similarly, the strong force can bind nucleons into nuclei even though nucleons have no strong-force charge. However, while the usual strong force between quarks falls off like 1/r^2 + a constant, the residual force between nucleons falls off like e^(-r/r0)/r, where r0 is a characteristic length scale (about 10^-15 meters).

    Sort of. Actually, electromagnetism only looks like a "field force" at long distances: at short distances we need to describe it in terms of particles (photons). The same is probably true of gravity but we can't probe at short enough distances to confirm that. For the strong force, we pretty much always have to talk about particles, because the force does not extend far enough for there to be much long-distance physics to talk about. Note that the above discussion of how the strong force falls off with distance is implicitly a field-ish concept, and should therefore be taken with a lot of salt.
  5. Oct 17, 2012 #4
    In terms of exchange particles, the strong force is mediated by gluons. It has infinite range like the electromagnetic force but in contrast to it, gluons themselves are charged and therefore can not spread through all of space. They always confine quarks and themselves into bound states, the hadrons.

    The residual strong forces that act in between these hadrons can be thought of as mediated by other hadrons. There are various models to describe this in detail, but roughly since hadrons are always massive, the range of the interaction will fall off with the inverse mass of the hadron that is exchanged.
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