Question on relationships between nuclear models

In summary, the conversation discusses two nuclear models, the liquid-drop model and the shell model, and their compatibility. The speaker suggests that these models are complimentary rather than contradictory, and that they are both crude approximations of what is happening within the nucleus. They also mention the EMC Effect and the limitations of these models. The conversation ends with a mention of more accurate models such as the parton model and lattice, but their computational complexity makes them less commonly used.
  • #1
Wormaldson
21
0
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.
 
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  • #2
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.
 
  • #3
K^2 said:
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.

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?
 
  • #4
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.
 
  • #5
one can find different nuclear models and relevant thing in book 'nuclear models' by greiner.
 

Related to Question on relationships between nuclear models

1. What are the different nuclear models?

There are three main nuclear models: the Liquid Drop Model, the Shell Model, and the Collective Model. The Liquid Drop Model describes the nucleus as a droplet of incompressible nuclear matter, the Shell Model explains the nuclear structure in terms of energy levels and nucleons filling those levels, and the Collective Model considers the nucleus as a vibrational system.

2. How do these nuclear models differ from each other?

The main difference between these models lies in their approach to describing the nuclear structure. The Liquid Drop Model treats the nucleus as a uniform liquid, while the Shell Model considers the nucleons as individual particles occupying specific energy levels. The Collective Model, on the other hand, describes the nucleus as a system of collective vibrations.

3. Which nuclear model is the most accurate?

Each nuclear model has its own strengths and limitations, and there is no single model that can fully explain the behavior of all nuclei. However, the Shell Model has been the most successful in predicting the properties of stable nuclei, while the Liquid Drop Model is better at describing the properties of very heavy and highly excited nuclei.

4. How do these nuclear models help us understand nuclear reactions?

Nuclear models provide a theoretical framework for understanding the behavior of nuclei and their interactions. By using these models, scientists can predict the behavior of nuclei in various nuclear reactions, such as fission or fusion. This information is crucial for applications in fields such as nuclear energy and medicine.

5. Are there any current developments in nuclear modeling?

Yes, there are ongoing efforts to improve and expand upon existing nuclear models. For example, there are efforts to combine the Liquid Drop Model and the Shell Model to create a more comprehensive model that can describe both stable and unstable nuclei. Additionally, advances in computer simulations have allowed for more complex and accurate models to be developed.

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