Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question on relationships between nuclear models

  1. Dec 12, 2012 #1
    So far in my physics education I've developed a basic understanding of two nuclear models, the liquid-drop model and the shell model.

    I read something a while ago (don't have the text on hand to quote the exact phrasing, unfortunately) that seemed to imply, in a couple of places, at least some degree of mutual-incompatibility between the two models. This seemed odd to me because as well as both models making accurate predictions, I'm not aware of any important features of either model that strike me as being explicitly contradictory. Stanger still is the idea that although both models are decent approximations of reality, only one of them is actually "true" (this may just be me reading too much into what I read, but it's the impression I got).

    What seemed more reasonable to me is that the models are complimentary - that is, the liquid drop model is derived from nuclear geometry, and the shell model is based on a QM approach to the nucleus, but the two are both (at least approximately) "true," so to speak, with each model arriving at compatible predictions based on different data, experiments and assumptions. But I could be completely wrong, of course.

    If anyone could shed some insight onto how nuclear models actually relate to each other, it would be much appreciated.
  2. jcsd
  3. Dec 12, 2012 #2


    User Avatar
    Science Advisor

    Both are crude approximations of what's going on within the nucleus. For a good example of where both models completely fail, consider the EMC Effect.

    As far as incompatibility between liquid-drop and shell models, they make completely different predictions for how the nucleons are distributed within the nucleus. The surprising result here is that liquid-drop model manages to make good predictions on binding energies within the nucleus, because it's based on assumptions that really aren't all that reasonable on the scale of a nucleus.
  4. Dec 13, 2012 #3
    Hm. That's very interesting. Is there any particular reason why it still works besides being unreasonable?

    And as a follow-up question, are there more accurate models currently in use?
  5. Dec 14, 2012 #4


    User Avatar
    Science Advisor

    I don't actually know if there is a specific good reason for drop model to work. But I don't work with nuclei, so I'm not the best person to ask.

    As far as better models, we definitely have them, but they tend to be computationally complex, which is why liquid-drop model and shell models with effective potential are used in the first place.

    Parton model is certainly an improvement. Problem is, you can get away with modeling a deuterium, maybe 3He, and that's about it. Then you have to start cutting corners. But even with parton model, a lot of information is lost. (I have to pull some tricks to get parton distribution function for a single meson.)

    Then there is lattice, of course, but I don't know if they do any calculations with multiple baryons.
  6. Dec 14, 2012 #5
    one can find different nuclear models and relevant thing in book 'nuclear models' by greiner.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook